{"id":207402,"date":"2025-07-08T09:10:58","date_gmt":"2025-07-08T01:10:58","guid":{"rendered":"https:\/\/server.hk\/cnblog\/207402\/"},"modified":"2025-07-08T09:10:58","modified_gmt":"2025-07-08T01:10:58","slug":"golang-%e4%b8%ad%e7%9a%84%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2%e5%a6%82%e4%bd%95%e5%b7%a5%e4%bd%9c%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/207402\/","title":{"rendered":"golang \u4e2d\u7684\u7c7b\u578b\u8f6c\u6362\u5982\u4f55\u5de5\u4f5c\uff1f"},"content":{"rendered":"

<\/b> <\/p>\n

\u5f53\u524d\u4f4d\u7f6e\uff1a ><\/span> ><\/span> ><\/span> ><\/span> golang \u4e2d\u7684\u7c7b\u578b\u8f6c\u6362\u5982\u4f55\u5de5\u4f5c\uff1f<\/span><\/p>\n

\u6765\u6e90\uff1astackoverflow<\/span>
\n2024-04-22 12:09:35<\/span>
\n<\/i>0\u6d4f\u89c8<\/span>
\n<\/i>\u6536\u85cf<\/span> <\/p>\n

\u201c\u7eb5\u6709\u75be\u98ce\u6765\uff0c\u4eba\u751f\u4e0d\u8a00\u5f03\u201d\uff0c\u8fd9\u53e5\u8bdd\u9001\u7ed9\u6b63\u5728\u5b66\u4e60Golang<\/span>\u7684\u670b\u53cb\u4eec\uff0c\u4e5f\u5e0c\u671b\u5728\u9605\u8bfb\u672c\u6587\u300agolang \u4e2d\u7684\u7c7b\u578b\u8f6c\u6362\u5982\u4f55\u5de5\u4f5c\uff1f\u300b<\/span>\u540e\uff0c\u80fd\u591f\u771f\u7684\u5e2e\u52a9\u5230\u5927\u5bb6\u3002\u6211\u4e5f\u4f1a\u5728\u540e\u7eed\u7684\u6587\u7ae0\u4e2d\uff0c\u9646\u7eed\u66f4\u65b0Golang<\/span>\u76f8\u5173\u7684\u6280\u672f\u6587\u7ae0\uff0c\u6709\u597d\u7684\u5efa\u8bae\u6b22\u8fce\u5927\u5bb6\u5728\u8bc4\u8bba\u7559\u8a00\uff0c\u975e\u5e38\u611f\u8c22\uff01<\/p>\n

\u95ee\u9898\u5185\u5bb9
\n <\/p>\n

\u6211\u7684\u95ee\u9898\u9648\u8ff0\u662f\u52a0\u8f7d\u548c\u4fdd\u5b58\u5e26\u6709\u6570\u5b57\u7684\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u8fd9\u4e9b\u6570\u5b57\u53ef\u4ee5\u8f7b\u677e\u5b58\u50a8\u5728 uint32\/float32<\/code> \u4e2d\u3002\u8fd9\u5c06\u5728\u78c1\u76d8\u4e0a\u5927\u7ea6\u8d85\u8fc7 2gb\uff0c\u5e76\u4e14\u6240\u6709\u5185\u5bb9\u4e5f\u90fd\u9700\u8981\u5728\u5185\u5b58\u4e2d\u3002<\/p>\n

\u6211\u7684\u7a0b\u5e8f\u9700\u8981\u5927\u91cf\u6570\u5b66\u8fd0\u7b97\uff0cgolang\u6807\u51c6\u5e93\u51fd\u6570\/\u65b9\u6cd5\u9700\u8981int\/float64<\/code>\u53c2\u6570\uff0c\u6211\u5fc5\u987b\u5c06\u6211\u7684\u6570\u5b57\u8f6c\u6362\u4e3aint\/float64<\/code><\/p>\n

\u4e00\u4e2a\u7b80\u5355\u7684\u57fa\u51c6\u6d4b\u8bd5\uff08https:\/\/play.golang.org\/p\/a52-wbo3z34\uff09\u7ed9\u51fa\u4e86\u4ee5\u4e0b\u8f93\u51fa\uff1a<\/p>\n

$: go test -bench=. \ngoos: linux\ngoarch: amd64\npkg: gotrade\nBenchmarkCast-4             1000       1519964 ns\/op\nBenchmarkNoCast-4           3000        373340 ns\/op\nPASS\nok      gotrade 2.843s<\/pre>\n
\u8fd9\u6e05\u695a\u5730\u8868\u660e\u7c7b\u578b\u8f6c\u6362\u76f8\u5f53\u6602\u8d35\u3002<\/p>\n
int \u548c float64 \u7684\u7f3a\u70b9\uff1a<\/p>\n
    \n
  • \u5b83\u51e0\u4e4e\u9700\u8981\u53cc\u500d\u7684\u5185\u5b58<\/li>\n<\/ul>\n
    int \u548c float64 \u7684\u4f18\u70b9\uff1a<\/p>\n
      \n
    • \u907f\u514d\u5927\u91cf\u7c7b\u578b\u8f6c\u6362\u64cd\u4f5c<\/li>\n<\/ul>\n
      \u8bf7\u5efa\u8bae\u6211\u4e00\u79cd\u5904\u7406\u8fd9\u79cd\u60c5\u51b5\u7684\u65b9\u6cd5\uff0c\u6211\u5728\u8fd9\u91cc\u9057\u6f0f\u4e86\u4ec0\u4e48\u5417\uff1f<\/p>\n
      \u5982\u679c\u6211\u4eec\u9700\u8981\u901a\u8fc7\u6807\u51c6\u5e93\u8fdb\u884c\u5916\u90e8\u8ba1\u7b97\uff0c\u6211\u4eec\u662f\u5426\u5e94\u8be5\u59cb\u7ec8\u9009\u62e9 int<\/code> \u548c float64<\/code> \uff1f<\/p>\n
       <\/p>\n
      \u89e3\u51b3\u65b9\u6848<\/h2>\n
       <\/p>\n
      \u60a8\u7684\u903b\u8f91\u3001\u57fa\u51c6\u548c\u5047\u8bbe\u5b58\u5728\u4e00\u4e9b\u9519\u8bef\u3002<\/p>\n
      \u81f3\u4e8e\u5f3a\u5236\u8f6c\u6362\uff0c\u60a8\u7684\u7ed3\u679c\u663e\u793a\u60a8\u7684 for \u5faa\u73af\u8fd0\u884c\u4e86 1000 \u6b21\u3002\u7531\u4e8e\u5faa\u73af 100 \u4e07\u6b21\uff0c\u8fd9\u5b9e\u9645\u4e0a\u8fdb\u884c\u4e86 10 \u4ebf\u6b21\u8f6c\u6362\u64cd\u4f5c\u2026\u2026\u8fd8\u4e0d\u9519\u3002<\/p>\n
      \u5b9e\u9645\u4e0a\uff0c\u6211\u7a0d\u5fae\u4fee\u6539\u4e86\u4f60\u7684\u4ee3\u7801\uff1a<\/p>\n
      const (\n    min = float64(math.smallestnonzerofloat32)\n    max = float64(math.maxfloat32)\n)\n\nfunc cast(in float64) (out float32, err error) {\n\n    \/\/ we need to guard here, as casting from float64 to float32 looses precision\n    \/\/ therefor, we might get out of scope.\n    if in < min {\n        return 0.00, fmt.errorf(\"%f is smaller than smallest float32 (%f)\", in, min)\n    } else if in > max {\n        return 0.00, fmt.errorf(\"%f is bigger than biggest float32 (%f)\", in, max)\n    }\n\n    return float32(in), nil\n}\n\n\/\/ multi64 uses a variadic in parameter, in order to be able\n\/\/ to use the multiplication with arbitrary length.\nfunc multi64(in ...float64) (result float32, err error) {\n\n    \/\/ necessary to set it to 1.00, since float64's null value is 0.00...\n    im := float64(1.00)\n\n    for _, v := range in {\n        im = im * v\n    }\n\n    \/\/ we only need to cast once.\n    \/\/ you do want to make the calculation with the original precision and only\n    \/\/ want to do the casting once. however, this should not be done here - but in the\n    \/\/ caller, as the caller knows on how to deal with special cases.\n    return cast(im)\n}\n\n\/\/ multi32 is a rather non-sensical wrapper, since the for loop\n\/\/ could easily be done in the caller.\n\/\/ it is only here for comparison purposes.\nfunc multi32(in ...float32) (result float32) {\n    result = 1.00\n    for _, v := range in {\n        result = result * v\n    }\n    return result\n}\n\n\/\/ openfile is here for comparison to show that you can do\n\/\/ a... fantastic metric ton of castings in comparison to io ops.\nfunc openfile() error {\n    f, err := os.open(\"cast.go\")\n    if err != nil {\n        return fmt.errorf(\"error opening file\")\n    }\n    defer f.close()\n\n    br := bufio.newreader(f)\n    if _, _, err := br.readline(); err != nil {\n        return fmt.errorf(\"error reading line: %s\", err)\n    }\n\n    return nil\n}<\/pre>\n
      \u4f7f\u7528\u4ee5\u4e0b\u6d4b\u8bd5\u4ee3\u7801<\/p>\n
      func init() {\n    rand.seed(time.now().utc().unixnano())\n}\nfunc benchmarkcast(b *testing.b) {\n    b.stoptimer()\n\n    v := rand.float64()\n    var err error\n\n    b.resettimer()\n    b.starttimer()\n\n    for i := 0; i < b.n; i++ {\n        if _, err = cast(v); err != nil {\n            b.fail()\n        }\n    }\n}\n\nfunc benchmarkmulti32(b *testing.b) {\n    b.stoptimer()\n\n    vals := make([]float32, 10)\n\n    for i := 0; i < 10; i++ {\n        vals[i] = rand.float32() * float32(i+1)\n    }\n\n    b.resettimer()\n    b.starttimer()\n\n    for i := 0; i < b.n; i++ {\n        multi32(vals...)\n    }\n}\nfunc benchmarkmulti64(b *testing.b) {\n\n    b.stoptimer()\n\n    vals := make([]float64, 10)\n    for i := 0; i < 10; i++ {\n        vals[i] = rand.float64() * float64(i+1)\n    }\n\n    var err error\n    b.resettimer()\n    b.starttimer()\n\n    for i := 0; i < b.n; i++ {\n        if _, err = multi64(vals...); err != nil {\n            b.log(err)\n            b.fail()\n        }\n    }\n}\n\nfunc benchmarkopenfile(b *testing.b) {\n    var err error\n    for i := 0; i < b.n; i++ {\n        if err = openfile(); err != nil {\n            b.log(err)\n            b.fail()\n        }\n    }\n}<\/pre>\n
      \u4f60\u4f1a\u5f97\u5230\u8fd9\u6837\u7684\u4e1c\u897f<\/p>\n
      BenchmarkCast-4         1000000000           2.42 ns\/op\nBenchmarkMulti32-4       300000000           5.04 ns\/op\nBenchmarkMulti64-4       200000000           8.19 ns\/op\nBenchmarkOpenFile-4         100000          19591 ns\/op<\/pre>\n
      \u56e0\u6b64\uff0c\u5373\u4f7f\u4f7f\u7528\u8fd9\u79cd\u76f8\u5bf9\u611a\u8822\u4e14\u672a\u7ecf\u4f18\u5316\u7684\u4ee3\u7801\uff0c\u8087\u4e8b\u8005\u4ecd\u7136\u662f openfile \u57fa\u51c6\u6d4b\u8bd5\u3002<\/p>\n
      \u73b0\u5728\uff0c\u8ba9\u6211\u4eec\u6b63\u786e\u770b\u5f85\u8fd9\u4e00\u70b9\u3002 19,562ns \u7b49\u4e8e 0,019562 \u6beb\u79d2\u3002\u4e00\u822c\u4eba\u53ef\u4ee5\u611f\u77e5\u5230\u7684\u5ef6\u8fdf\u7ea6\u4e3a 20 \u6beb\u79d2\u3002\u56e0\u6b64\uff0c\u5373\u4f7f\u662f 100,000\uff08\u201c\u5341\u4e07\u201d<\/em>\uff09\u6587\u4ef6\u6253\u5f00\u3001\u884c\u8bfb\u53d6\u548c\u6587\u4ef6\u5173\u95ed\u4e5f\u6bd4\u4eba\u7c7b\u611f\u77e5\u7684\u901f\u5ea6\u5feb 1000 \u500d\u3002<\/p>\n
      \u4e0e\u6b64\u76f8\u6bd4\uff0c\u8f6c\u6362\u901f\u5ea6\u8981\u5feb\u51e0\u4e2a\u6570\u91cf\u7ea7<\/em><\/strong> – \u6240\u4ee5\u4f60\u53ef\u4ee5\u968f\u610f\u8f6c\u6362\uff0c\u4f60\u7684\u74f6\u9888\u5c06\u662f i\/o\u3002<\/p>\n
      \u7f16\u8f91<\/h2>\n
      \u8fd9\u7559\u4e0b\u4e86\u4e00\u4e2a\u95ee\u9898\uff0c\u4e3a\u4ec0\u4e48\u60a8\u4e0d\u9996\u5148\u5c06\u503c\u5bfc\u5165\u4e3a float64\uff1f<\/p>\n
      \u7406\u8bba\u8981\u638c\u63e1\uff0c\u5b9e\u64cd\u4e0d\u80fd\u843d\uff01\u4ee5\u4e0a\u5173\u4e8e\u300agolang \u4e2d\u7684\u7c7b\u578b\u8f6c\u6362\u5982\u4f55\u5de5\u4f5c\uff1f\u300b\u7684\u8be6\u7ec6\u4ecb\u7ecd\uff0c\u5927\u5bb6\u90fd\u638c\u63e1\u4e86\u5427\uff01\u5982\u679c\u60f3\u8981\u7ee7\u7eed\u63d0\u5347\u81ea\u5df1\u7684\u80fd\u529b\uff0c\u90a3\u4e48\u5c31\u6765\u5173\u6ce8\u516c\u4f17\u53f7\u5427\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
      \u5f53\u524d\u4f4d\u7f6e\uff1a > > ...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-207402","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207402","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=207402"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207402\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=207402"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=207402"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=207402"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}