{"id":65,"date":"2013-08-24T03:53:27","date_gmt":"2013-08-23T19:53:27","guid":{"rendered":"http:\/\/blog.stlover.org\/?p=65"},"modified":"2013-08-28T09:40:46","modified_gmt":"2013-08-28T01:40:46","slug":"%e7%a6%bb%e6%95%a3%e5%82%85%e7%ab%8b%e5%8f%b6%e5%ad%a6%e4%b9%a0","status":"publish","type":"post","link":"http:\/\/blog.xuhao1.me\/?p=65","title":{"rendered":"\u79bb\u6563\u5085\u7acb\u53f6\u5b66\u4e60\u4e4bFFT"},"content":{"rendered":"<p>FFT\uff0c\u5feb\u901f\u5085\u7acb\u53f6\u53d8\u6362\u662f\u4e2a\u86ee\u6709\u610f\u601d\u7684\u73a9\u610f\uff0c\u5e94\u7528\u5f88\u5e7f\uff0c\u5c24\u5176\u5728\u4fe1\u606f\u5904\u7406\u65b9\u9762\uff0c\u6700\u8fd1\u9700\u8981\u7528\u5230\uff0c\u5c31\u5b66\u5b66\u5566\u3002<\/p>\n<p>\u4e07\u4e8b\u5f00\u5934\u96be\uff0c\u5148\u505a\u4e2a\u7b80\u5355\u7684\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\u3002<\/p>\n<p>\u4ec0\u4e48\u662f\u5085\u7acb\u53f6\u53d8\u6362\uff0c\u5c31\u4e0d\u591a\u89e3\u91ca\u4e86\uff0c\u5c31\u662f\u628a\u51fd\u6570\u6253\u6210\u4e00\u5806\u6ce2\uff0c\u4e0d\u61c2\u7684\u8bf7\u51fa\u95e8\u5de6\u8f6c\u53bb\u4ea4\u91cd\u4fee\u8d39\u3002<\/p>\n<p><!--more--><\/p>\n<p>\u4e00\uff0c\u4ec0\u4e48\u662f\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\uff08DFT\uff09<\/p>\n<p>\u8be6\u7ec6\u5185\u5bb9\u89c1\uff1ahttp:\/\/zh.wikipedia.org\/wiki\/%E7%A6%BB%E6%95%A3%E5%82%85%E9%87%8C%E5%8F%B6%E5%8F%98%E6%8D%A2<\/p>\n<p>\u867d\u7136\u6211\u89c9\u5f97\u6211\u7528\u56fe\u62cd\u5b83\u62cd\u7684\u66f4\u6e05\u695a\u3002<\/p>\n<p>\u81f3\u4e8e\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\uff0c\u5219\u662f\u5e94\u7528\u4e8e\u5b9e\u8df5\u7684\u5bf9\u4fe1\u53f7\u91c7\u6837\u7684\u5085\u7acb\u53f6\u53d8\u6362\u7b97\u6cd5\uff0c\u65e0\u59a8\u6211\u4eec\u5148\u7528mathematica\u751f\u6210\u4e00\u4e2a4096\u4f4d\u7684\u4fe1\u53f7\uff0c\u501f\u7528mathematica\u6765\u4e86\u89e3\u4e0b\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\uff0c\u6298\u817e\u534a\u5929\u7ec8\u4e8e\u641e\u61c2\u4e86\u79bb\u6563\u5085\u7acb\u53f6\u7684\u5de5\u4f5c\u539f\u7406\u3002\u9996\u5148\u6211\u4eec\u901a\u8fc7\u4e00\u4e2a\u6f14\u793a\u6765\u8bf4\u4e0b.<\/p>\n<p>\u9996\u5148\u7528mathematica\u505a\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u51fd\u6570\u53d1\u751f\u5668\u3002<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"pun\">(*<\/span><span class=\"typ\">Mathematica<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Code<\/span><span class=\"pun\">*)<\/span><\/li>\n<li class=\"L1\"><span class=\"typ\">SignalMk<\/span><span class=\"pun\">[<\/span><span class=\"pln\">t_<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Omega<\/span><span class=\"pln\">_<\/span><span class=\"pun\">]<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">:=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">(<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"typ\">Omega<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">200<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0f<\/span><span class=\"pun\">[<\/span><span class=\"pln\">x_<\/span><span class=\"pun\">]<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">:=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Sin<\/span><span class=\"pun\">[<\/span><span class=\"pln\">x<\/span><span class=\"pun\">*<\/span><span class=\"typ\">Omega<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">]<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">+<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Sin<\/span><span class=\"pun\">[<\/span><span class=\"lit\">2<\/span><span class=\"pln\">\u00a0x<\/span><span class=\"pun\">*<\/span><span class=\"typ\">Omega<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"typ\">Signal<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Table<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0f<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"pln\">i<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">*<\/span><span class=\"pln\">t<\/span><span class=\"pun\">}];(*\u5047\u8bbe<\/span><span class=\"lit\">1<\/span><span class=\"pun\">\u79d2\u91c7\u6837<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">\u4e2a<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"typ\">Return<\/span><span class=\"pun\">[<\/span><span class=\"typ\">Signal<\/span><span class=\"pun\">]<\/span><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"pun\">)<\/span><\/li>\n<\/ol>\n<p>\u6211\u4eec\u5982\u679c\u53d6<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><span class=\"typ\">SignalMk<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0.1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">200<\/span><span class=\"pun\">]]<\/span><\/li>\n<\/ol>\n<p>\u751f\u6210\u4e00\u4e2a\u65f6\u957f0.1\u79d2\uff0comega\u4e3a200\u7684\u56fe\u50cf\u5982\u4e0b<\/p>\n<p><a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/anal.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-70\" alt=\"anal\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/anal.jpg\" width=\"666\" height=\"406\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/anal.jpg 666w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/anal-300x182.jpg 300w\" sizes=\"(max-width: 666px) 100vw, 666px\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>\u4e00\u4e2a\u4e8c\u4e8c\u7684\u56fe\u50cf\uff0c\u4e8e\u662f\u6211\u4eec\u628a\u5b83\u6254\u5230mathematica\u81ea\u5e26\u7684\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u5316\u91cc\u9762\u89c2\u5bdf\u4e0b\u3002<\/p>\n<p>\u4e0b\u9762\u662f\u8001\u957f\u7684\u4ee3\u7801<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"typ\">Table<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0ts\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">10<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0sig\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">SignalMk<\/span><span class=\"pun\">[<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Omega<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"typ\">Print<\/span><span class=\"pun\">[<\/span><span class=\"str\">&#8220;omega\u00a0is&#8221;<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Omega<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0dr\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">100<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0P1\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Abs<\/span><span class=\"pun\">[<\/span><span class=\"typ\">Fourier<\/span><span class=\"pun\">[<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">FourierParameters<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">&#8211;<\/span><span class=\"lit\">1<\/span><span class=\"pun\">}]]<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">)[[<\/span><span class=\"lit\">1<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">;;<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">]],<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">All<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">DataRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">}*(<\/span><span class=\"lit\">2<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Pi<\/span><span class=\"pun\">)\/<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotStyle<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Red<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0P2\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Re<\/span><span class=\"pun\">[<\/span><span class=\"typ\">Fourier<\/span><span class=\"pun\">[<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">FourierParameters<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">&#8211;<\/span><span class=\"lit\">1<\/span><span class=\"pun\">}]])<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">[[<\/span><span class=\"lit\">1<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">;;<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">]],<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">All<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">DataRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">}*(<\/span><span class=\"lit\">2<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Pi<\/span><span class=\"pun\">])\/<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotStyle<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Blue<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0P3\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Im<\/span><span class=\"pun\">[<\/span><span class=\"typ\">Fourier<\/span><span class=\"pun\">[<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">FourierParameters<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">&#8211;<\/span><span class=\"lit\">1<\/span><span class=\"pun\">}]]<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">)[[<\/span><span class=\"lit\">1<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">;;<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">]],<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">All<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">DataRange<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0dr<\/span><span class=\"pun\">*<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">}*(<\/span><span class=\"lit\">2<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Pi<\/span><span class=\"pun\">)\/<\/span><span class=\"pln\">ts<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">PlotStyle<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">-&gt;<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Yellow<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"typ\">Show<\/span><span class=\"pun\">[<\/span><span class=\"pln\">P1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0P2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0P3<\/span><span class=\"pun\">]<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<\/ol>\n<p>\u751f\u6210\u4e00\u7cfb\u5217\u4eceomega\u4e3a100-150-200\u7684\u5085\u7acb\u53f6\u540e\u7684\u56fe\u50cf\uff0c\u5982\u4e0b<\/p>\n<p><a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/50fly.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-71\" alt=\"50fly\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/50fly.jpg\" width=\"681\" height=\"408\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/50fly.jpg 681w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/50fly-300x179.jpg 300w\" sizes=\"(max-width: 681px) 100vw, 681px\" \/><\/a> <a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/100fly.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-72\" alt=\"100fly\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/100fly.jpg\" width=\"666\" height=\"399\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/100fly.jpg 666w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/100fly-300x179.jpg 300w\" sizes=\"(max-width: 666px) 100vw, 666px\" \/><\/a> <a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/200fly.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-73\" alt=\"200fly\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/200fly.jpg\" width=\"652\" height=\"392\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/200fly.jpg 652w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/200fly-300x180.jpg 300w\" sizes=\"(max-width: 652px) 100vw, 652px\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>\u53ef\u89c1\u5728\u6b63\u786e\u7684\u5730\u65b9\u51fa\u73b0\u4e86\u5c16\u5cf0\uff0c\u4e5f\u5c31\u662f\u6211\u4eec\u5f97\u5230\u4e86\u4e00\u4e2a\u6f02\u4eae\u9891\u8c31\u7684\u5206\u5e03\u3002<\/p>\n<p>\u90a3\u4e48\u6765\u89e3\u91ca\u4e00\u4e0bdft\uff08\u79bb\u6563\u5085\u7acb\u53f6\uff09\u5427\uff0c<\/p>\n<p>\u6240\u8c13\u79bb\u6563\u5085\u7acb\u53f6\uff0c\u5c31\u662f\u628a\u79bb\u6563\u5316\u7684\u6570\u636e\u70b9\u8f6c\u5316\u4e3a\u4e00\u4e2a\u79bb\u6563\u7684\u5085\u7acb\u53f6\u7ea7\u6570\uff0c\u7528\u6765\u83b7\u5f97\u9891\u8c31\u5206\u6790\u7b49\uff0c\u5728\u4e2a\u9886\u57df\u90fd\u6709\u5f88\u5927\u7528\u9014\uff0c\u5176\u672c\u8d28\u5c31\u662f\u4e00\u5806\u6570\u636e\u70b9\uff0c\u6309\u7167\u65f6\u5e8f\u8fdb\u884c\u3002\u8f6c\u6362\u4e3a\u4e00\u4e2a\u9891\u7387\uff0d\u632f\u5e45\u7684\u5206\u5e03\uff0c<\/p>\n<p>\u5176\u4e2d<\/p>\n<p>$$!\\omega_k=k\\cdot\\frac{2\\pi}{NT}$$<\/p>\n<p>T\u4e3a\u91c7\u6837\u9891\u7387\uff0cN\u4e3a\u91c7\u6837\u6570\u91cf\uff0cNT\u4e3a\u91c7\u6837\u603b\u65f6\u957f\uff0ck\u4e3a\u7f16\u53f7,k\u4e3a\u53d8\u6362\u540e\u7684\u6837\u70b9\uff08\u5728\u8ba1\u7b97\u673a\u4e2d\u4e00\u822c\u662f\u632f\u5e45\u7684\u6807\u53f7\uff09<\/p>\n<p>\u4e5f\u5c31\u662f\u6211\u4e0a\u9762\u751f\u6210\u9891\u8c31\u56fe\u7684\u7cfb\u6570\u3002\u5bf9\u5e94\u7684\u5c06\u662f\u4e00\u4e2a\u632f\u5e45\uff0c\u53cd\u4e4b\u6211\u4eec\u53ef\u4ee5\u7528\u9006\u53d8\u6362\u628a\u5b83\u53d8\u56de\u53bb\u3002<\/p>\n<p>\u4e8e\u662f\u539f\u4fe1\u53f7\u5c31\u53ef\u4ee5\u8868\u793a\u6210<\/p>\n<p>$$\\sum_{k=0}^{n-1}Re[f(k)]\\cdot Cos(\\omega_{k}t)+Im[f(k)]\\cdot Sin(\\omega_{k}t)$$<\/p>\n<p>\u65e0\u59a8\u4e00\u8bd5\uff0c\u53c8\u662fmathematica<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"pun\">(*<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Mathematica<\/span><span class=\"pln\">\u00a0code<\/span><span class=\"pun\">*)<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">sig\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">SignalMk<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0.5<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">200<\/span><span class=\"pun\">];(*\u751f\u6210\u4e00\u4e2a0.5\u79d2\u957f\uff0c200omega\u7684\u4fe1\u53f7*)<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">fx\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Fourier<\/span><span class=\"pun\">[<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">];(*\u628a\u8fd9\u73a9\u610f\u5085\u7acb\u53f6\u4e86*)<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">omgk<\/span><span class=\"pun\">[<\/span><span class=\"pln\">k_<\/span><span class=\"pun\">]<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">:=<\/span><span class=\"pln\">\u00a0k\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"lit\">2<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Pi<\/span><span class=\"pun\">)\/<\/span><span class=\"lit\">0.5\/\/k\u5bf9\u5e94\u7684omega<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">y\u00a0<\/span><span class=\"pun\">=<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Table<\/span><span class=\"pun\">[<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Sum<\/span><span class=\"pun\">[<\/span><span class=\"typ\">Re<\/span><span class=\"pun\">[<\/span><span class=\"pln\">fx<\/span><span class=\"pun\">[[<\/span><span class=\"pln\">k\u00a0<\/span><span class=\"pun\">+<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">1<\/span><span class=\"pun\">]]]*<\/span><span class=\"typ\">Cos<\/span><span class=\"pun\">[<\/span><span class=\"pln\">omgk<\/span><span class=\"pun\">[<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]*<\/span><span class=\"pln\">t<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">](*\u6ce8\u610f\u4e0a\u9762\u63d0\u5230\u7684k\u662f0\u5f00\u59cb\u7f16\u53f7\uff0cmathematica\u9ed8\u8ba41\u5f00\u59cb\uff0c\u6545\u6709\uff0b1\uff0c\u6b64\u9879\u65e0\u59a8\u8ba4\u4e3a\u662f\u793a\u6ce2\u5668\u7684\u90a3\u4e2a\u201c\u76f4\u6d41\u6210\u5206\u201d*)<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">+<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Im<\/span><span class=\"pun\">[<\/span><span class=\"pln\">fx<\/span><span class=\"pun\">[[<\/span><span class=\"pln\">k\u00a0<\/span><span class=\"pun\">+<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">1<\/span><span class=\"pun\">]]]*<\/span><span class=\"typ\">Sin<\/span><span class=\"pun\">[<\/span><span class=\"pln\">omgk<\/span><span class=\"pun\">[<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]*<\/span><span class=\"pln\">t<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">]<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"pln\">k<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">500<\/span><span class=\"pun\">}]<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0 \u00a0(*\u8fd9\u4e2a\u5f0f\u5b50\u542f\u793a\u5c31\u662f\u5b9a\u4e49\u4e86*)<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">{<\/span><span class=\"pln\">t<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">2048<\/span><span class=\"pun\">}];<\/span><\/li>\n<li class=\"L2\"><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">]<\/span><\/li>\n<li class=\"L3\"><span class=\"typ\">ListLinePlot<\/span><span class=\"pun\">[<\/span><span class=\"pln\">y<\/span><span class=\"pun\">]<\/span><\/li>\n<\/ol>\n<p>\u5f97\u5230\u4e24\u5e45\u56fe<\/p>\n<p><a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/redft0.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-86\" alt=\"redft0\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/redft0.jpg\" width=\"477\" height=\"287\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/redft0.jpg 477w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/redft0-300x180.jpg 300w\" sizes=\"(max-width: 477px) 100vw, 477px\" \/><\/a> <a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/redft1.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-87\" alt=\"redft1\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/redft1.jpg\" width=\"527\" height=\"321\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/redft1.jpg 527w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/redft1-300x182.jpg 300w\" sizes=\"(max-width: 527px) 100vw, 527px\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>\u5206\u8fa8\u4e0d\u51fa\u6765\u90a3\u4e2a\u662f\u4fe1\u53f7\u6e90\u7684\u90a3\u4e2a\u662f\u91cd\u65b0\u9006\u5085\u7acb\u53f6\u56de\u53bb\u7684\uff1f\u90a3\u5c31\u662f\u9a8c\u8bc1\u6210\u529f\u4e86\u3002<\/p>\n<p><span style=\"line-height: 1.5;\">\u4e8c\uff0c\u7b80\u5355\u7684\u4e00\u7ef4\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362<\/span><\/p>\n<p>Now\uff0c\u6211\u4eec\u5148\u6487\u5f00Mathematica\u548cwiki\uff0c\u81ea\u5df1\u63a8\u5012\u4e00\u4e0b\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\u3002<\/p>\n<p>\u6253\u5f00\u6211\u4eec\u7684\u5fae\u79ef\u5206\u6559\u6750\uff0c\u8fde\u7eed\u5085\u7acb\u53f6\u53d8\u6362\u5982\u662f\u5b9a\u4e49<\/p>\n<p>$$!F(\\omega)=\\frac{1}{l}\\intop_{0}^{+l}f(t)e^{-i\\omega t}dt$$<\/p>\n<p>\u8fd9\u662f\u5bf9\u4e8e\u8fde\u7eed\u51fd\u6570\u7684\u79ef\u5206\uff0c\u5f53\u7136\u6211\u4eec\u4e0d\u80fd\u76f4\u63a5\u5b9e\u73b0\uff0c\u4e8e\u662f\u4e4e\uff0c\u6211\u4eec\u5f97\u628a\u5b83\u79bb\u6563\u5316\uff0c\u5f88\u5f00\u5fc3\u7684\u76f4\u63a5\u77e9\u9635\u79ef\u4e2a\u5206\u597d\u5566<\/p>\n<p>\u6211\u4eec\u8ba9\u91c7\u6837\u5468\u671f\u4e3a\u6700\u5c0f\u5206\u5ea6dt\u4e5f\u5c31\u662f$$\\frac{L}{N}(s)=T$$<\/p>\n<p>\u90a3\u4e48\u5f97\u5230\u5f0f\u5b50<\/p>\n<p>$$!F(\\omega)=\\frac{1}{l}\\sum_{k=0}^{n-1}f(k\\cdot T)e^{-i\\omega k\\cdot T}T$$<\/p>\n<p>\u5176\u4e2d\uff0ck\uff1d0, \u6b64\u5904\u4e0ewikipedia\u7565\u6709\u4e0d\u540c\uff0c\u5f52\u4e00\u5316\u5f97\u5230<\/p>\n<p>$$!F[l]=\\sum_{k=0}^{k-1}f(k)e^{-i\\frac{2\\pi}{N}k\\cdot l}$$<\/p>\n<p>\u6b64\u65f6\u9700\u8981\u6ce8\u610f\u7684\u662f\u5f97\u5230\u7684\u7cfb\u6570\u5e76\u975e\u6211\u4eec\u6700\u540e\u4f7f\u7528\u7684\uff0c\u4e2d\u95f4\u8fd8\u6709\u4e00\u4e2a\u5f52\u4e00\u5316\u7cfb\u6570\uff0c\u4e0d\u8fc7\u8fd9\u4e2a\u6682\u4e14\u65e0\u5173\u7d27\u8981\uff0c\u636e\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u5199\u51fa\u7b2c\u4e00\u4e2a\u7b80\u5355\u7684o(n^2)\u7684dft\u7a0b\u5e8f<\/p>\n<p>\u9996\u5148\uff0cc\u7b49\u8bed\u8a00\u662f\u4e0d\u652f\u6301\u865a\u6570\u7684\uff0c\u6d69\u6d69\u53c8\u4e0d\u60f3\u5b66fortran\uff0c\u4e8e\u662f\u5148\u8f6c\u4e3a\u4e24\u4e2a\u90e8\u5206<\/p>\n<p>$$!F[i].Re=\\sum_{k=0}^{k-1}f(k)\\cdot Cos(2\\cdot\\pi\\cdot k\\cdot i\/N)$$<\/p>\n<p>$$!F[i].Im=-\\sum_{k=0}^{k-1}f(k)\\cdot Sin(2\\cdot\\pi\\cdot k\\cdot i\/N)$$<\/p>\n<p>$$!F[i].Abs=Sqrt(F[i].Re^2+F[i].Im^2)$$<\/p>\n<p>\u4e8e\u662f\u4e4e\uff0crush\u4e00\u4e2a\u5c0fc\u7684\u7a0b\u5e8f\uff0c\u5c31\u662f\u6211\u4eec\u7684\u6162\u901f\u5085\u7acb\u53f6\u4e86\uff0c\u4e3a\u4e86\u8003\u8651\u5411\u5355\u7247\u673a\u8fc1\u79fb\uff0c\u4ee3\u7801\u98ce\u683c\u662f\u7eafc\u7684\u98ce\u683c\uff0c\u5927\u91cf\u6307\u9488\u6beb\u65e0\u7ed3\u6784\u6beb\u65e0\u7f8e\u611f\uff0c\u5404\u4f4d\u5c06\u5c31\u770b\u54c8\u3002<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"com\">#include<\/span><span class=\"str\">&#8220;stdio.h&#8221;<\/span><\/li>\n<li class=\"L1\"><span class=\"com\">#include<\/span><span class=\"str\">&#8220;stdlib.h&#8221;<\/span><\/li>\n<li class=\"L2\"><span class=\"com\">#include<\/span><span class=\"str\">&#8220;math.h&#8221;<\/span><\/li>\n<li class=\"L3\"><span class=\"com\">#define<\/span><span class=\"pln\">\u00a0pi\u00a0<\/span><span class=\"lit\">3.1415926<\/span><\/li>\n<li class=\"L4\"><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">\u00a0dft<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*&gt;<\/span><span class=\"pln\">re<\/span><span class=\"pun\">,<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*&gt;<\/span><span class=\"pln\">im<\/span><span class=\"pun\">)<\/span><span class=\"com\">\/\/return\u00a0abs \u6162\u901fdft\u6838\u5fc3<\/span><\/li>\n<li class=\"L5\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">abs<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">*<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0re<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">*<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0im<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">*<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0sumre<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0sumim<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0k<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">k<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sumre<\/span><span class=\"pun\">+=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]*<\/span><span class=\"pln\">cosf<\/span><span class=\"pun\">(<\/span><span class=\"lit\">2<\/span><span class=\"pun\">*<\/span><span class=\"pln\">pi<\/span><span class=\"pun\">*<\/span><span class=\"pln\">k<\/span><span class=\"pun\">*<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><span class=\"com\">\/\/calculate\u00a0re<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sumim<\/span><span class=\"pun\">-=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]*<\/span><span class=\"pln\">sinf<\/span><span class=\"pun\">(<\/span><span class=\"lit\">2<\/span><span class=\"pun\">*<\/span><span class=\"pln\">pi<\/span><span class=\"pun\">*<\/span><span class=\"pln\">k<\/span><span class=\"pun\">*<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"pln\">sumre<\/span><span class=\"pun\">&gt;<\/span><span class=\"lit\">4000<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0printf<\/span><span class=\"pun\">(<\/span><span class=\"str\">&#8220;%d\\n&#8221;<\/span><span class=\"pun\">,<\/span><span class=\"pln\">sumre<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0re<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">sumre<\/span><span class=\"pun\">\/<\/span><span class=\"pln\">sqrtf<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0im<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">sumim<\/span><span class=\"pun\">\/<\/span><span class=\"pln\">sqrtf<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><span class=\"com\">\/\/\u53d6\u5f52\u4e00\u5316\u7cfb\u6570\u90fd\u662fsqrt(n)<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0abs<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">sqrtf<\/span><span class=\"pun\">(<\/span><span class=\"pln\">sumre<\/span><span class=\"pun\">*<\/span><span class=\"pln\">sumre<\/span><span class=\"pun\">+<\/span><span class=\"pln\">sumim<\/span><span class=\"pun\">*<\/span><span class=\"pln\">sumim<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0abs<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L5\"><span class=\"pun\">}<\/span><\/li>\n<li class=\"L6\"><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">SignalMk<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0time<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0omega<\/span><span class=\"pun\">)\/\/\u4fe1\u53f7\u53d1\u751f\u5668<\/span><\/li>\n<li class=\"L7\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">int<\/span><span class=\"pun\">)<\/span><span class=\"pln\">time<\/span><span class=\"pun\">*<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">*<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sig<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">sinf<\/span><span class=\"pun\">(<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">((<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)<\/span><span class=\"pln\">i<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">omega<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">)+<\/span><span class=\"pln\">sinf<\/span><span class=\"pun\">(<\/span><span class=\"pln\">\u00a0<\/span><span class=\"lit\">2<\/span><span class=\"pun\">*((<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)<\/span><span class=\"pln\">i<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">omega<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0sig<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L5\"><span class=\"pun\">}<\/span><\/li>\n<li class=\"L6\"><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0main<\/span><span class=\"pun\">()<\/span><\/li>\n<li class=\"L7\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">re<\/span><span class=\"pun\">,*<\/span><span class=\"pln\">im<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">=<\/span><span class=\"typ\">SignalMk<\/span><span class=\"pun\">(<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"lit\">200<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0printf<\/span><span class=\"pun\">(<\/span><span class=\"str\">&#8220;Build\u00a0Sucessful\\n&#8221;<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">abs<\/span><span class=\"pun\">=<\/span><span class=\"pln\">dft<\/span><span class=\"pun\">(<\/span><span class=\"pln\">sig<\/span><span class=\"pun\">,<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">,<\/span><span class=\"pln\">re<\/span><span class=\"pun\">,<\/span><span class=\"pln\">im<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0printf<\/span><span class=\"pun\">(<\/span><span class=\"str\">&#8220;dft\u00a0Sucessful\\n&#8221;<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">FILE<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">fp<\/span><span class=\"pun\">=<\/span><span class=\"pln\">fopen<\/span><span class=\"pun\">(<\/span><span class=\"str\">&#8220;d.txt&#8221;<\/span><span class=\"pun\">,<\/span><span class=\"str\">&#8220;w&#8221;<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0fprintf<\/span><span class=\"pun\">(<\/span><span class=\"pln\">fp<\/span><span class=\"pun\">,<\/span><span class=\"str\">&#8220;%f\u00a0&#8220;<\/span><span class=\"pun\">,<\/span><span class=\"pln\">abs<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]);<\/span><\/li>\n<li class=\"L6\"><span class=\"pun\">}<\/span><\/li>\n<\/ol>\n<p>\u4e8e\u662f\uff0c\u7ed3\u679c\u5bfc\u5165\u4e86mathematica\u5f97\u5230\u4e86\u4e0b\u9762\u7684\u56fe<\/p>\n<p><a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/slowdft.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-97\" alt=\"slowdft\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/slowdft.jpg\" width=\"782\" height=\"484\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/slowdft.jpg 782w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/slowdft-300x185.jpg 300w\" sizes=\"(max-width: 767px) 89vw, (max-width: 1000px) 54vw, (max-width: 1071px) 543px, 580px\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>So cool!<\/p>\n<p>\u8fd9\u5c31\u662f\u90a3\u4e2a\u7b80\u5355\u7684c\u7a0b\u7684\u7ed3\u679c\u3002\u67d0\u79cd\u610f\u4e49\u4e0a\uff0c\u6211\u4eec\u5df2\u7ecf\u5b9e\u73b0\u4e86\u591a\u6570\u7684\u4fe1\u53f7\u5904\u7406\u3002<\/p>\n<p>\u4e09\uff0c\u4e3b\u9898\uff0cFFT\uff01\u6548\u7387\uff0c\u8fd8\u662f\u6548\u7387<\/p>\n<p>\u5bf9\u4e8e\u6570\u5b57\u4fe1\u53f7\u5904\u7406\uff0c\u8dd1\u572812MHz\u5355\u7247\u673a\u5403\u7740\u65e0\u53ef\u5fcd\u8010\u7684\u7834\u70c2\u73af\u5883\u8fd8\u8981\u5e72\u6700\u91cd\u7684\u6d3b\uff0c\u6211\u771f\u63d0\u5355\u7247\u673a\u7a0b\u5e8f\u5458\u611f\u5230\u6349\u6025\uff08\u4ee5\u524d\u73a9\u5355\u7247\u673a\u7684\u70ed\u60c5\u5c31\u662f\u88ab\u786c\u4ef6\u8d44\u6e90\u7184\u706d\u7684\uff0c\u76f8\u6bd4\u800c\u8a00\u6211\u66f4\u613f\u610f\u57288 cores\u4e3b\u673a\u5199\u975e\u7ed3\u6784\u7f51\u683cCFD\uff09\u3002\u4e8e\u662f\uff0c\u8fd9\u4e2a\u6548\u7387\u662f$$O(n^2)$$\u7b80\u76f4\u4e0d\u80fd\u5fcd\u6709\u6ca1\u6709\u3002\u3002\u3002\u8bbe\u60f3\u6211\u4eec\u8981\u5206\u6790\u4e00\u4e2a\u4eba\u7684\u58f0\u97f3\u6765\u786e\u5b9a\u4ed6\u7684\u8eab\u4efd\uff0c\u5085\u7acb\u53f6\u53d8\u6362\u662f\u57fa\u7840\u4e86\uff0c\u53ef\u662f\uff01mp3\u91c7\u6837\u7387\u662f44,100 Hz \uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c<\/p>\n<p>\u67d0\u9634\u68ee\u7684\u5730\u4e0b\u4f1a\u573a\uff0c\u7537A\u9053\uff0c\u201c\u4f60\u597d\u3002\u201d\uff0c\u8017\u65f6\u4e00\u79d2<\/p>\n<p>\u7537B\u6697\u9053\uff0c\u5f85\u6211\u5206\u6790\u4e0b\u5b83\u7684\u58f0\u97f3\u662f\u5426\u6b63\u786e\u3002<\/p>\n<p>\u7ecf\u8fc7\u4e86\u6f2b\u957f\u7684162\u79d2\uff08\u7528\u6211\u4eec\u7684slowdft\u9700\u898144100*44100\u6b21\u8fd0\u7b97\uff0c51\u5355\u7247\u673a\u9700\u8981162\u79d2\uff09\u3002\u672c\u62c9\u767b\u5df2\u7ecf\u6210\u529f\u8131\u8eab\u3002<\/p>\n<p>\u6216\u8005<\/p>\n<p>\u82e6\u82e6\u601d\u8003\uff0c\u67ef\u5357\u60f3\u5230\u4e86\u8bc1\u4eba\u662f\u8c01\uff0c\u6253\u5f00\u53d8\u58f0\u5668\uff0c\u8bf4\u4e86\u4e00\u6bb560\u79d2\u949f\u7684\u63a8\u7406\uff0c\u7ecf\u8fc7\u5355\u7247\u673a\u81ea\u71c3\u7684\u6e29\u5ea6\u7684162\u5c0f\u65f6\u8fd0\u7b97\uff0c<\/p>\n<p>\u72af\u4eba\u9003\u8dd1\u4e86\u3002<\/p>\n<p>&nbsp;<\/p>\n<p>\u8fd9\u6837\u4e0d\u5982\u627e\u5757\u8c46\u8150\u649e\u6b7b\u597d\u4e86\u3002\u4e8e\u662f\u4e4e\uff0cfft\u6a2a\u7a7a\u51fa\u4e16\u3002<\/p>\n<p>FFT\u662f\u4e00\u79cd\u590d\u6742\u5ea6\u4e3aNLog(N)\u7684\u7b97\u6cd5\uff0c\u4e00\u822c\u770b\u5230\u8fd9\u4e2a\u6548\u7387\uff0c\u5c31\u4f1a\u5f88\u660e\u4e86\u8fd9\u662f\u4e00\u4e2a\u4e8c\u5206\u6784\u9020\u7684\u8fc7\u7a0b\uff0c\u6574\u4e2a\u7b97\u6cd5\u5fc5\u7136\u5b58\u5728\u4e00\u5b9a\u7684\u5bf9\u79f0\u6027\uff0c\u800c\u4e14\u51e0\u4e4e\u53ef\u4ee5\u8ba4\u5b9a\u662f\u5b58\u5728\u9012\u5f52\u8fc7\u7a0b\u3002\u5269\u4e0b\u8981\u505a\u7684\u5c31\u662f\u627e\u5230\u90a3\u4e2a\u7b80\u5355\u7684\u9012\u5f52\u51fd\u6570\uff0c\u7136\u540e\u5f97\u5230\u6211\u4eec\u7684\u8fd0\u7b97\u7ed3\u679c\u3002\u4e0d\u8fc7\u5728\u8fd9\u91cc\uff0c\u7b97\u6cd5\u5bf9\u79f0\u6027\u5012\u662f\u7531\u6570\u5b66\u7ed9\u51fa\u7684\u3002<\/p>\n<p>\u53c2\u8003\uff1ahttp:\/\/zh.wikipedia.org\/wiki\/%E5%BF%AB%E9%80%9F%E5%82%85%E9%87%8C%E5%8F%B6%E5%8F%98%E6%8D%A2<\/p>\n<p>\u6211\u4eec\u7528$$W_N$$\u8868\u793a$$e^{-j\\frac{2\\pi}{N}}$$\uff0c\u4e8e\u662f\u4e4e<\/p>\n<p>$$!W_{N}^{k+N}=W_{N}^{k}$$<\/p>\n<p>$$!W_{N}^{k+\\frac{N}{2}}=-W_{N}^{k}$$<\/p>\n<p>$$!W_{N}^{m\\cdot k_{n}}=W_{\\frac{N}{m}}^{k_{n}}$$<\/p>\n<p>\u6839\u636e\u8fd9\u4e2a\uff0c\u6211\u4eec\u53ef\u4ee5\u5f97\u5230\u8fd9\u6837\u4e00\u4e2a\u9012\u5f52\u6784\u9020\u8fc7\u7a0b\uff08\u5728\u6b64\u6211\u5012\u66f4\u5b81\u613f\u7528\u8ba1\u7b97\u673a\u4e0a\u7684\u65b9\u5f0f\u800c\u975e\u7eaf\u7cb9\u6570\u5b66\u8bed\u8a00\u8868\u8ff0\uff09\u3002<\/p>\n<p>\u4e00\u822c\uff0c\u5bf9\u4e8e\u6b64\u7c7b\u95ee\u9898\u90fd\u662f\u5148\u5206\u89e3\u4e3a\u6734\u7d20\u9012\u5f52\uff0c\u7136\u540e\u627e\u5230\u91cd\u590d\u4f7f\u7528\u7684\u8c03\u7528\uff08\u6bd4\u5982\u5b8c\u5168\u76f8\u540c\u7684\u53c2\u6570\u8f93\u5165\uff09\uff0c\u5f97\u5230\u7ed3\u679c\uff0c\u662f\u4e3a\u8ba1\u5212\u641c\u7d22\u3002<\/p>\n<p>F(N,k)=<\/p>\n<p>If(k&lt;=$$\\frac{N}{2}$$)<\/p>\n<p>$$F_{even}(k)+W_N^kF_{odd}(k)$$<\/p>\n<p>If(k&gt;$$\\frac{N}{2}$$)<\/p>\n<p>$$F_{even}(k-\\frac{N}{2})-W_N^{k-\\frac{N}{2}}F_{odd}(k-\\frac{N}{2})$$<\/p>\n<p>\u7531\u6b64\u53ef\u4ee5\u9012\u5f52\u6784\u9020\u51faF(k)<\/p>\n<p>\u4e8e\u662f\uff0c\u6211\u5199\u4e86\u8fd9\u6837\u4e00\u4e2a\u9012\u5f52<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0dfftk<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">input\u00a0<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0k<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L1\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">even<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">odd<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><span class=\"com\">\/\/\u7b5b\u9009\u5668<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"pln\">i<\/span><span class=\"pun\">%<\/span><span class=\"lit\">2<\/span><span class=\"pun\">==<\/span><span class=\"lit\">0<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0even<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">else<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0odd<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">==<\/span><span class=\"lit\">1<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0input<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0<\/span><span class=\"pun\">]*<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"lit\">0<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&lt;=<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">even<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">)+<\/span><span class=\"pln\">W<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">odd<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">else<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">(<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">even<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&#8211;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">)-<\/span><span class=\"pln\">W<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&#8211;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">odd<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&#8211;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"lit\">0<\/span><span class=\"pun\">,<\/span><span class=\"lit\">0<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L8\"><span class=\"pun\">}<\/span><\/li>\n<\/ol>\n<p>\u7136\u540e\u4e3b\u51fd\u6570\u8fd9\u4e48\u641e<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">fft<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L1\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">*<\/span><span class=\"pln\">res<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"pln\">i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0res<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">i<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0res<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L7\"><span class=\"pun\">}<\/span><\/li>\n<\/ol>\n<p>\u4e8e\u662f\u5f97\u5230\u4e86\u6f02\u4eae\u7684\u7ed3\u679c<\/p>\n<p><a href=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/fft0.jpg\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-114\" alt=\"fft0\" src=\"http:\/\/blog.stlover.org\/wp-content\/uploads\/2013\/08\/fft0.jpg\" width=\"782\" height=\"484\" srcset=\"http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/fft0.jpg 782w, http:\/\/blog.xuhao1.me\/wp-content\/uploads\/2013\/08\/fft0-300x185.jpg 300w\" sizes=\"(max-width: 767px) 89vw, (max-width: 1000px) 54vw, (max-width: 1071px) 543px, 580px\" \/><\/a><\/p>\n<p>\u55ef\uff01\u8fd9\u5c31\u662f\u6211\u4eec\u60f3\u8981\u7684\uff0c\u73b0\u5728\u4e07\u4e8b\u4ff1\u5907\uff0c\u53ea\u6b20\u4e1c\u98ce\uff1a\u5982\u4f55\u8ba9\u5b83\u5feb\u8d77\u6765\u3002<\/p>\n<p>\u56db\uff1a\u96d5\u866b\u5c0f\u6280<\/p>\n<p>\u8ba9\u6211\u4eec\u5728\u56de\u987e\u4e0b\u6211\u4eec\u7684\u51fd\u6570\u8f93\u5165\uff0c\u5047\u5b9a\u8ba1\u7b97\u7684\u90fd\u662f2\u7684\u6307\u6570\uff0c\u51fd\u6570\u7684\u7ed3\u679c\u4f9d\u8d56\u4e8e<\/p>\n<p>1.\u70b9\u96c6\u5408\uff1ainput\uff0c\u5305\u542bSize\u4fe1\u606f\u3002<\/p>\n<p>2.k\u7684\u503c\u3002<\/p>\n<p>so\uff0c\u70b9\u96c6\u5408\u662f\u4e00\u4e2a\u9887\u4e3a\u865a\u65e0\u98d8\u6e3a\u7684\u6982\u5ff5\uff0c\u90a3\u6211\u4eec\u600e\u4e48\u786e\u5b9a\u5b83\u5462\uff0c\u6ce8\u610f\u5230\u6211\u4eec\u5047\u5b9a\u6570\u91cf\u4e00\u76f4\u662f\u4e8c\u7684\u6307\u6570\uff0c\u800c\u4e14\u4e00\u76f4\u4e8c\u5206\uff0c\u90a3\u4e48\uff0c\u53ea\u8981\u8bf4\u4e00\u4e2a\u70b9\u96c6\u5408\u7684Size\uff0c\u6211\u4eec\u5c31\u80fd\u786e\u5b9a\u4e8c\u5206\u4e86\u591a\u5c11\u6b21\uff0c\u7ed9\u51fa\u7b2c\u4e00\u4e2a\u70b9\u7684\u5168\u5c40\u7f16\u53f7\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u5728\u8fd9\u68f5\u67e5\u627e\u6811\u4e0a\u786e\u5b9a\u4ed6\u7684\u4f4d\u7f6e\u3002\u4e8e\u662f\uff0c\u5bf9\u4e8e\u6bcf\u6b21\u641c\u7d22\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u4ee5\u4e0b\u51e0\u4e2a\u70b9\u6807\u540d\u5176\u610f\u4e49<\/p>\n<p>\u6df1\u5ea6\uff0c\u9996\u4f4d\u7f16\u53f7\uff0c\u4ee5\u53cak\u3002<\/p>\n<p>\u5728\u8ba1\u7b97\u4e2d\uff0c\u6211\u4eec\u8981\u505a\u5bf9\u534a\u4f18\u5316\uff0c\u5176\u5b9e\u53ea\u9700\u5728k&lt;Size\/2\u65f6\u5019\u628a+Size\/2\u52a0\u4e0a\u3002<\/p>\n<p>\u4e8e\u662f\u4e4e\uff1a<\/p>\n<ol class=\"linenums\">\n<li class=\"L0\"><span class=\"kwd\">bool<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Travel<\/span><span class=\"pun\">[<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">][<\/span><span class=\"lit\">13<\/span><span class=\"pun\">][<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">]={<\/span><span class=\"lit\">0<\/span><span class=\"pun\">};\/\/\u7eaa\u5f55\u662f\u5426\u8bbf\u95ee\u8fc7<\/span><\/li>\n<li class=\"L1\"><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0val<\/span><span class=\"pun\">[<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">][<\/span><span class=\"lit\">13<\/span><span class=\"pun\">][<\/span><span class=\"lit\">4096<\/span><span class=\"pun\">];\/\/\u7eaa\u5f55\u8bbf\u95ee\u8fc7\u7684\u503c<\/span><\/li>\n<li class=\"L2\"><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0numheight<\/span><span class=\"pun\">[<\/span><span class=\"lit\">15<\/span><span class=\"pun\">]={<\/span><span class=\"lit\">0<\/span><span class=\"pun\">};<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0<\/span><\/li>\n<li class=\"L4\"><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0dfftk<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pun\">*<\/span><span class=\"pln\">nums\u00a0<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0k<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L5\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0h<\/span><span class=\"pun\">=<\/span><span class=\"pln\">log<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">)\/<\/span><span class=\"pln\">log<\/span><span class=\"pun\">(<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0top<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0top<\/span><span class=\"pun\">=<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Travel<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">])\/\/\u8bbf\u95ee\u8fc7\u5c31\u76f4\u63a5\u7528<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"pln\">val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Travel<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]=<\/span><span class=\"lit\">1<\/span><span class=\"pun\">;\/\/\u6807\u5b9a\u4e3a\u8bbf\u95ee\u8fc7<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">even<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pun\">*<\/span><span class=\"pln\">evenums<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">odd<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">float<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pun\">*<\/span><span class=\"pln\">oddnums<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)\/\/\u5947\u5076\u5206\u6d41<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"pln\">i<\/span><span class=\"pun\">%<\/span><span class=\"lit\">2<\/span><span class=\"pun\">==<\/span><span class=\"lit\">0<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0even<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0evenums<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">else<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0odd<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0oddnums<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">];<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">==<\/span><span class=\"lit\">1<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0<\/span><span class=\"pun\">]][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]=(<\/span><span class=\"pln\">input<\/span><span class=\"pun\">[<\/span><span class=\"lit\">0<\/span><span class=\"pun\">]*<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"lit\">1<\/span><span class=\"pun\">,<\/span><span class=\"lit\">0<\/span><span class=\"pun\">));<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"pln\">val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">if<\/span><span class=\"pun\">(<\/span><span class=\"pln\">k<\/span><span class=\"pun\">&lt;=<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">{<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0everes<\/span><span class=\"pun\">,<\/span><span class=\"pln\">oddres<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L5\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0everes<\/span><span class=\"pun\">=<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">even<\/span><span class=\"pun\">,<\/span><span class=\"pln\">evenums<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L6\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0oddres<\/span><span class=\"pun\">=<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">odd<\/span><span class=\"pun\">,<\/span><span class=\"pln\">oddnums<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]=(<\/span><span class=\"pln\">everes<\/span><span class=\"pun\">+<\/span><span class=\"pln\">W<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">oddres<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Travel<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">+<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=<\/span><span class=\"lit\">1<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">+<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">\/<\/span><span class=\"lit\">2<\/span><span class=\"pun\">]=(<\/span><span class=\"pln\">everes<\/span><span class=\"pun\">&#8211;<\/span><span class=\"pln\">W<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">k<\/span><span class=\"pun\">)*<\/span><span class=\"pln\">oddres<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"pln\">val<\/span><span class=\"pun\">[<\/span><span class=\"pln\">top<\/span><span class=\"pun\">][<\/span><span class=\"pln\">h<\/span><span class=\"pun\">][<\/span><span class=\"pln\">k<\/span><span class=\"pun\">]);<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"pun\">}<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0printf<\/span><span class=\"pun\">(<\/span><span class=\"str\">&#8220;You\u00a0are\u00a0Wrong\\n&#8221;<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">(<\/span><span class=\"lit\">0<\/span><span class=\"pun\">,<\/span><span class=\"lit\">0<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L4\"><span class=\"pun\">}<\/span><\/li>\n<li class=\"L5\"><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">fft<\/span><span class=\"pun\">(<\/span><span class=\"typ\">float<\/span><span class=\"pun\">*<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">)<\/span><\/li>\n<li class=\"L6\"><span class=\"pun\">{<\/span><\/li>\n<li class=\"L7\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">*<\/span><span class=\"pln\">res<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">Complex<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">Complex<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L8\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0i<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L9\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">=(<\/span><span class=\"typ\">int<\/span><span class=\"pln\">\u00a0<\/span><span class=\"pun\">*)<\/span><span class=\"pln\">malloc<\/span><span class=\"pun\">(<\/span><span class=\"kwd\">sizeof<\/span><span class=\"pun\">(<\/span><span class=\"typ\">int<\/span><span class=\"pun\">)*<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L0\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"pln\">i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L1\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0nums<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">i<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L2\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">for<\/span><span class=\"pun\">(<\/span><span class=\"pln\">i<\/span><span class=\"pun\">=<\/span><span class=\"lit\">0<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">&lt;<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">;<\/span><span class=\"pln\">i<\/span><span class=\"pun\">++)<\/span><\/li>\n<li class=\"L3\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0res<\/span><span class=\"pun\">[<\/span><span class=\"pln\">i<\/span><span class=\"pun\">]=<\/span><span class=\"pln\">dfftk<\/span><span class=\"pun\">(<\/span><span class=\"pln\">input<\/span><span class=\"pun\">,<\/span><span class=\"pln\">nums<\/span><span class=\"pun\">,<\/span><span class=\"typ\">Size<\/span><span class=\"pun\">,<\/span><span class=\"pln\">i<\/span><span class=\"pun\">);<\/span><\/li>\n<li class=\"L4\"><span class=\"pln\">\u00a0\u00a0\u00a0\u00a0<\/span><span class=\"kwd\">return<\/span><span class=\"pln\">\u00a0res<\/span><span class=\"pun\">;<\/span><\/li>\n<li class=\"L5\"><span class=\"pun\">}<\/span><\/li>\n<\/ol>\n<p>\u8dd1\u4e00\u4e0b\uff0c\u7ed3\u679c\u672a\u53d8\uff0c\u65f6\u95f4\u4ece<b>24646\u53d8\u6210\u4e86189\u6beb\u79d2\u3002\u3002\u3002\u3002\u3002\u8fd9\u5dee\u8ddd<\/b><\/p>\n<p>\u4e8e\u662f\uff0c\u65f6\u95f4\u5f97\u5230\u4e86\u4f18\u5316\uff0c\u518d\u56de\u5934\u770b\u6211\u4eec\u7684\u6570\u7ec4\uff0c\u6709\u4ec0\u4e48\u4e0d\u5bf9\u4e48\uff1f<\/p>\n<p>$$N^2*Log_2N$$\u7684\u7a7a\u95f4\uff1f\u4f60\u5728\u9017\u6211\u561b\uff1f<\/p>\n<p>\u4e94\uff0c\u4e27\u5fc3\u75c5\u72c2<\/p>\n<p>\u72b6\u6001\u538b\u7f29\uff1a<\/p>\n<p>\u9996\u5148\u770b\u8fd9\u4e2a\u8bb0\u5f55\uff0c\u6211\u4eec\u6b64\u65f6\u9700\u8981\u8ba1\u7b97\u4e00\u4e0b\u6211\u4eec\u771f\u6b63\u9700\u8981\u8bb0\u5f55\u7684\u6570\u91cf\uff0c\u4ece\u4e00\u5230k\u6b21\u6b21\u4e8c\u5206\uff0c\u5171\u6709$$NLog_2N$$\u4e2a\u72b6\u6001\uff0c\u5176\u4e2d\u6709\u4e00\u534a\u662f\u4f5c\u4e3ak&lt;Size\/2return\u7ed9\u51fa\u7684\uff0c\u4e00\u534a\u662f\u4f5c\u4e3a\u8bb0\u5f55\u7684\u3002\u4e8e\u662f\u6211\u4eec\u9700\u8981\u7cbe\u786e\u6784\u9020\u4e00\u4e2a\u65b0\u7684\u8bb0\u5f55\uff0c\u4f7f\u5f97\u8fd9\u4e2a\u5b58\u50a8\u91cf\u5927\u5e45\u5ea6\u51cf\u5c11\u3002<\/p>\n<p>\u9996\u5148\uff0c\u5f53\u7136\u662f\u6beb\u65e0\u8282\u64cd\u7684\u76f4\u63a5stl::Map\u4e86\uff08\u672c\u6765\u51c6\u5907\u81ea\u5df1\u5199\u4e2ahash\u6765\u7740\u3002\u3002\u56f0\u4e86\u3002\u3002\u3002\u53bb\u4ed6\u7684\u7eafc\u5e73\u53f0\uff09\u3002\u3002\u3002\u4e8e\u662f\u3002<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>FFT\uff0c\u5feb\u901f\u5085\u7acb\u53f6\u53d8\u6362\u662f\u4e2a\u86ee\u6709\u610f\u601d\u7684\u73a9\u610f\uff0c\u5e94\u7528\u5f88\u5e7f\uff0c\u5c24\u5176\u5728\u4fe1\u606f\u5904\u7406\u65b9\u9762\uff0c\u6700\u8fd1\u9700\u8981\u7528\u5230\uff0c\u5c31\u5b66\u5b66\u5566\u3002 \u4e07\u4e8b\u5f00\u5934\u96be\uff0c &hellip; <\/p>\n<p class=\"link-more\"><a href=\"http:\/\/blog.xuhao1.me\/?p=65\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201c\u79bb\u6563\u5085\u7acb\u53f6\u5b66\u4e60\u4e4bFFT\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[5],"tags":[],"_links":{"self":[{"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/posts\/65"}],"collection":[{"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=65"}],"version-history":[{"count":39,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/posts\/65\/revisions"}],"predecessor-version":[{"id":126,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=\/wp\/v2\/posts\/65\/revisions\/126"}],"wp:attachment":[{"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=65"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=65"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.xuhao1.me\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=65"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}