{"id":2149,"date":"2016-08-28T22:23:54","date_gmt":"2016-08-28T14:23:54","guid":{"rendered":"http:\/\/boweihe.me\/?p=2149"},"modified":"2016-08-28T22:23:54","modified_gmt":"2016-08-28T14:23:54","slug":"%e9%99%a4%e6%b3%95%e7%9a%84%e6%95%88%e7%8e%87","status":"publish","type":"post","link":"https:\/\/dayandcarrot.space\/?p=2149","title":{"rendered":"\u9664\u6cd5\u7684\u6548\u7387"},"content":{"rendered":"<p>\u4f30\u8ba1\u5e94\u8be5\u90fd\u77e5\u9053\u7b97\u9664\u6cd5\u7684\u6548\u7387\u6bd4\u7b97+-*\u4f4e\u597d\u591a\uff0c\u90a3\u4e48\u5230\u5e95\u4f4e\u591a\u5c11\u5462\uff1f\u7b80\u5355\u5199\u4e86\u4e00\u4e2a\u7a0b\u5e8f\u6d4b\u8bd5\u770b\u770b\u3002<br \/>\n<strong>\u6ce8\u610f<\/strong>\uff1aavg0\u51fd\u6570\u53ef\u80fd\u4f1a\u78b0\u5230\u6ea2\u51fa\u7684\u60c5\u51b5\uff0c\u8fd9\u79cd\u65b9\u6cd5\u5c3d\u91cf\u4e0d\u8981\u7528\u3002<\/p>\n<ul>\n<li>avg0: \u7edf\u4e00\u52a0\u8d77\u6765\uff0c\u518d\u505a\u9664\u6cd5\uff1b<\/li>\n<li>avg1: \u52a0\u7684\u65f6\u5019\u5c31\u505a\u9664\u6cd5\uff1b<\/li>\n<li>avg2: \u52a0\u7684\u65f6\u5019\u4e58\u4ee5\u9884\u5148\u7b97\u597d\u7684\uff0c\u5206\u6bcd\u7684\u5012\u6570\uff1b<\/li>\n<\/ul>\n<pre class=\"lang:c++ decode:true \">void printDuration(clock_t start, clock_t end){\n    cout &lt;&lt; \"Time elapsed: \" &lt;&lt; (end - start)\/(float)CLOCKS_PER_SEC &lt;&lt; \" seconds.\" &lt;&lt; endl;\n}\ndouble avg0(int* ary, int N, long again){\n    cout &lt;&lt; \"avg0: \";\n    clock_t start = clock();\n    double sum;\n    while(again &gt; 0){\n        sum = 0;\n        for(int i=0; i&lt;N; i++)\n            sum += ary[i];\n        sum \/= (double)N;\n        again --;\n    }\n    clock_t end = clock();\n    printDuration(start, end);\n    return sum;\n}\ndouble avg1(int* ary, int N, long again){\n    cout &lt;&lt; \"avg1: \";\n    clock_t start = clock();\n    double sum = 0;\n    while(again &gt; 0){\n        for(int i=0; i&lt;N; i++)\n            sum += ary[i]\/(double)N;\n        again--;\n    }\n    clock_t end = clock();\n    printDuration(start, end);\n    return sum;\n}\ndouble avg2(int* ary, int N, long again){\n    cout &lt;&lt; \"avg2: \";\n    clock_t start = clock();\n    double sum = 0;\n    while(again &gt; 0){\n        double denominator = 1 \/ (double)N;\n        for(int i=0; i&lt;N; i++)\n            sum += ary[i] * denominator;\n        again--;\n    }\n    clock_t end = clock();\n    printDuration(start, end);\n    return sum;\n}\nint main() {\n    int N;\n    long again;\n    cin &gt;&gt; N &gt;&gt; again; \/\/num of numbers to be generated\n    srand(time(NULL));\n    int* ary = new int[N];\n    for(int i=0; i&lt;N; i++)\n        ary[i] = rand();\n    double r0 = avg0(ary, N, again);\n    double r1 = avg1(ary, N, again);\n    double r2 = avg2(ary, N, again);\n    return 0;\n}<\/pre>\n<p>\u7ed3\u679c\uff1a<\/p>\n<pre class=\"lang:default decode:true \">50000 50000\navg0: Time elapsed: 7.49197 seconds.\navg1: Time elapsed: 16.7689 seconds.\navg2: Time elapsed: 7.51349 seconds.\nProcess finished with exit code 0\n<\/pre>\n<p>\u6bd4\u4e00\u500d\u8fd8\u591a\u7684\u65f6\u95f4\uff01\u53ef\u6015\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4f30\u8ba1\u5e94\u8be5\u90fd\u77e5\u9053\u7b97\u9664\u6cd5\u7684\u6548\u7387\u6bd4\u7b97+-*\u4f4e\u597d\u591a\uff0c\u90a3\u4e48\u5230\u5e95\u4f4e\u591a\u5c11\u5462\uff1f\u7b80\u5355\u5199\u4e86\u4e00\u4e2a\u7a0b\u5e8f\u6d4b\u8bd5\u770b\u770b\u3002 \u6ce8\u610f\uff1aavg0\u51fd\u6570\u53ef\u80fd\u4f1a\u78b0\u5230\u6ea2\u51fa\u7684\u60c5\u51b5\uff0c\u8fd9\u79cd\u65b9\u6cd5\u5c3d\u91cf\u4e0d\u8981\u7528\u3002 avg0: \u7edf\u4e00\u52a0\u8d77\u6765\uff0c\u518d\u505a\u9664\u6cd5\uff1b avg1: \u52a0\u7684\u65f6\u5019\u5c31\u505a\u9664\u6cd5\uff1b avg2: \u52a0\u7684\u65f6\u5019\u4e58\u4ee5\u9884\u5148\u7b97\u597d\u7684\uff0c\u5206\u6bcd\u7684\u5012\u6570\uff1b void printDuration(clock_t start, clock_t end){ cout &lt;&lt; &#8220;Time elapsed: &#8221; &lt;&lt; (end &#8211; start)\/(float)CLOCKS_PER_SEC &lt;&lt; &#8221; seconds.&#8221; &lt;&lt; endl; } double avg0(int* ary, int N, long again){ cout &lt;&lt; &#8220;avg0: &#8220;; clock_t start = clock(); double sum; while(again &gt; 0){ sum = 0; for(int i=0; i&lt;N; i++) [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-2149","post","type-post","status-publish","format-standard","hentry","category-study"],"_links":{"self":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts\/2149","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2149"}],"version-history":[{"count":0,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts\/2149\/revisions"}],"wp:attachment":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2149"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2149"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2149"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}