{"id":2291,"date":"2022-12-11T20:10:33","date_gmt":"2022-12-11T19:10:33","guid":{"rendered":"https:\/\/ff.mhrooz.xyz\/?p=2291"},"modified":"2022-12-12T12:41:28","modified_gmt":"2022-12-12T11:41:28","slug":"openmp_zhong_de_shu_ju_gong_xiang_gui_ze_data_sharing_rules","status":"publish","type":"post","link":"https:\/\/blog.mhrooz.xyz\/index.php\/2022\/12\/11\/openmp_zhong_de_shu_ju_gong_xiang_gui_ze_data_sharing_rules\/","title":{"rendered":"OpenMP\u4e2d\u7684\u6570\u636e\u5171\u4eab\u89c4\u5219(data sharing rules)"},"content":{"rendered":"\n

Data-Sharing Rules<\/h1>\n\n\n\n

\u53d8\u91cf\u5728OpenMP\u4e2d\u53ef\u4ee5\u662f\u5171\u4eab(shared)\u8fd8\u662f\u79c1\u6709(private)\u7684\uff0c\u5171\u4eab\u548c\u79c1\u6709\u88ab\u79f0\u4f5c\u53d8\u91cfData-sharing\u7684\u5c5e\u6027\uff08attribute\uff09\u3002\u5982\u679c\u53d8\u91cf\u662f\u5171\u4eab\u7684\uff0c\u5728\u6240\u6709\u7ebf\u7a0b\u4e2d\u5b58\u5728\u4e00\u4e2a\u5b9e\u4f8b\u4f7f\u5f97\u8fd9\u4e2a\u53d8\u91cf\u88ab\u5171\u4eab\u3002\u5982\u679c\u53d8\u91cf\u662f\u79c1\u6709\u7684\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u5c06\u4f1a\u5f97\u5230\u79c1\u6709\u53d8\u91cf\u7684local copy\u3002<\/p>\n\n\n\n

Implicit Rules<\/h2>\n\n\n\n

OpenMP\u6709\u4e00\u7cfb\u5217\u89c4\u5219\uff0c\u6765\u63a8\u6d4b\u6570\u636e\u5171\u4eab\u7684\u5c5e\u6027(attributes)\u3002<\/p>\n\n\n\n

\u4f8b\u5982\uff0c\u8003\u8651\u4e0b\u9762\u8fd9\u6bb5\u4ee3\u7801\uff1a<\/p>\n\n\n\n

int i = 0; \nint n = 10; \nint a = 7;\n\n\u200b#pragma omp parallel for \nfor (i = 0; i < n; i++) {\n \u00a0 \u00a0int b = a + i; \u00a0 \n    ... \n}<\/pre>\n\n\n\n
\u67094\u4e2a\u53d8\u91cfi<\/code>,n<\/code>,a<\/code>,b<\/code>\u3002<\/p>\n\n\n\n
\u5728\u5e76\u884c\u533a\u57df\u4ee5\u5916\u58f0\u660e\u53d8\u91cf\u7684\u6570\u636e\u5171\u4eab\u5c5e\u6027\u901a\u5e38\u662f\u5171\u4eab\u7684\uff0cn<\/code>,a<\/code>\u662f\u5171\u4eab\u53d8\u91cf<\/p>\n\n\n\n
\u5bf9\u4e8e\u5faa\u73af\u8fed\u4ee3\u53d8\u91cf\uff0c\u9ed8\u8ba4\u662f\u79c1\u6709\u7684\uff0c\u56e0\u6b64i<\/code>\u662f\u79c1\u6709\u53d8\u91cf\u3002<\/p>\n\n\n\n
\u5728\u5e76\u884c\u533a\u57df\u5185\u90e8\u58f0\u660e\u7684\u53d8\u91cf\u662f\u79c1\u6709\u7684\uff0cb<\/code>\u662f\u79c1\u6709\u7684\u3002<\/p>\n\n\n\n
\u8fd9\u91cc\u5efa\u8bae\u58f0\u660e\u5728\u5faa\u73af\u5185\u90e8\u58f0\u660e\u5faa\u73af\u53d8\u91cf\uff0c\u8fd9\u6837\uff0c\u53d8\u91cf\u79c1\u6709\u5c31\u4f1a\u975e\u5e38\u660e\u786e\u3002<\/p>\n\n\n\n
int n = 10;                 \/\/ shared\nint a = 7;                  \/\/ shared\n\n#pragma omp parallel for \nfor (int i = 0; i < n; i++) \/\/ i private\n{\n    int b = a + i;          \/\/ b private\n    ...\n}<\/pre>\n\n\n\n
Explicit Rules<\/h2>\n\n\n\n
\u6211\u4eec\u53ef\u4ee5\u663e\u5f0f\u8bbe\u7f6e\u53d8\u91cfData-sharing\u7684\u5c5e\u6027\u3002<\/p>\n\n\n\n
Shared<\/h3>\n\n\n\n
shared(list)<\/code>\u5b50\u53e5\u58f0\u660e\u5728list\u4e2d\u7684\u53d8\u91cf\u90fd\u662f\u5171\u4eab\u7684\uff0c\u4f8b\u5b50\uff1a<\/p>\n\n\n\n
#pragma omp parallel for shared(n, a)\nfor (int i = 0; i < n; i++)\n{\n    int b = a + i;\n    ...        \n}<\/pre>\n\n\n\n
a<\/code>\u548cn<\/code>\u90fd\u662f\u5171\u4eab\u53d8\u91cf\u3002<\/p>\n\n\n\n
\u6ce8\u610fOpenMP\u6ca1\u6709\u7ed9\u51fa\u4e00\u4e2a\u673a\u5236\u6765\u9632\u6b62\u5171\u4eab\u53d8\u91cf\u4e4b\u95f4\u7684data race\u3002\u8fd9\u5e94\u8be5\u662f\u7a0b\u5e8f\u5458\u7684\u8d23\u4efb\u3002<\/p>\n\n\n\n
\u6240\u8c13data race\u5c31\u662f\u4e0d\u540c\u7ebf\u7a0b\u540c\u65f6\u8bfb\u5165\u4e00\u4e2a\u53d8\u91cf\uff0c\u4e0d\u540c\u65f6\u5199\u4e00\u4e2a\u53d8\u91cf\uff0c\u4f1a\u9020\u6210\u7ed3\u679c\u4e0d\u5bf9\u3002<\/p>\n\n\n\n
\u4f8b\u5982\uff1a<\/p>\n\n\n\n
\u505a\u6c42\u548c\uff0c\u56db\u4e2a\u7ebf\u7a0b\u9700\u8981\u5c06\u6c42\u51fa\u7684\u7ed3\u679c\u653e\u5728\u53d8\u91cfsum<\/code>\u91cc\u3002\u90a3\u4e48\u8fd9\u56db\u4e2a\u7ebf\u7a0b\u5982\u679c\u540c\u65f6\u8bfb\u5199sum\u53ef\u80fd\u4f1a\u51fa\u9519\uff08\u56db\u4e2a\u7ebf\u7a0b\u540c\u65f6\u8bfb\u5230\u4e00\u4e2a\u8001\u503c\uff0c\u5f97\u5230\u7684\u65b0\u503c\u5c06\u4ec5\u4ec5\u662f\u67d0\u4e00\u4e2a\u7ebf\u7a0b\u7684\u7ed3\u679c\u52a0\u5230sum\u91cc\uff09\u3002\u5177\u4f53\u6765\u8bf4\uff1a \u8bbesum=6,\u7ebf\u7a0b1\u5f97\u52301\uff0c\u7ebf\u7a0b2\u5f97\u52302\uff0c\u7ebf\u7a0b3\u5f97\u52303\uff0c\u7ebf\u7a0b4\u5f97\u52304\uff0c \u56db\u4e2a\u7ebf\u7a0b\u73b0\u5728\u60f3\u8981\u5c06\u7b97\u51fa\u6765\u7684\u7ed3\u679c\u540c\u65f6\u5199\u5230sum\u91cc\uff0c \u5047\u8bbe\u56db\u4e2a\u7ebf\u7a0b\u8fd0\u884c\u7684\u6c42\u548c\u4ee3\u7801\u4e3asum = sum + a;<\/code>\u5176\u4e2da\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u6c42\u5f97\u7684\u503c \u6b64\u65f6\u7b49\u5f0f\u53f3\u8fb9\u7684sum\u4e3a6\uff0c\u6240\u4ee5\u5bf9\u4e8e\u7ebf\u7a0b1\u6765\u8bf4\uff0c\u73b0\u5728\u8981\u8fd0\u884c\u7684\u5c31\u662fsum = 6 + 1<\/code>,\u5199\u5165\u5f97\u65b0sum=7\uff0c \u4f46\u662f\u7ebf\u7a0b2\u5728\u7ebf\u7a0b1\u5199\u5165\u524d\uff0c\u5c31\u5df2\u7ecf\u8bfb\u5230sum=6\uff0c\u90a3\u4e48\u5bf9\u4e8e\u7ebf\u7a0b2\uff0c\u8fd0\u884c\u7684\u5c31\u662fsum = 6 + 2<\/code>\uff0c\u5f97\u5230sum=8. \u5176\u4ed6\u4e24\u4e2a\u4f9d\u6b21\u7c7b\u63a8\uff0c \u6240\u4ee5\u6700\u7ec8\u5f97\u5230\u7684\u503c\u662f\u4ec0\u4e48\u4e0d\u786e\u5b9a\u3002<\/p>\n\n\n\n
\u5171\u4eab\u53d8\u91cf\u4f1a\u5f15\u5165\u989d\u5916\u5f00\u9500\uff0c\u56e0\u4e3a\u53d8\u91cf\u7684\u4e00\u4e2a\u5b9e\u4f8b\u5728\u591a\u4e2a\u7ebf\u7a0b\u4e4b\u95f4\u5171\u4eab\u3002\u5f53\u9700\u8981\u826f\u597d\u6027\u80fd\u65f6\u5019\uff0c\u5e94\u8be5\u5c3d\u91cf\u51cf\u5c11\u5171\u4eab\u53d8\u91cf\u7684\u6570\u91cf\u3002<\/p>\n\n\n\n
Private<\/h3>\n\n\n\n
private(list)<\/code>\u5b50\u53e5\u58f0\u660e\u5728list\u4e2d\u7684\u53d8\u91cf\u90fd\u662f\u79c1\u6709\u7684<\/p>\n\n\n\n
#pragma omp parallel for shared(n, a) private(b)\nfor (int i = 0; i < n; i++)\n{\n \u00a0 \u00a0b = a + i;\n\n \u00a0  ...\n}<\/pre>\n\n\n\n
\u8fd9\u91cc\u53d8\u91cfb<\/code>\u662f\u79c1\u6709\u53d8\u91cf\u3002\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6709\u53d8\u91cfb<\/code>\u7684local copy\u3002<\/p>\n\n\n\n
\u79c1\u6709\u53d8\u91cf\u6709\u65f6\u5019\u662f\u53cd\u76f4\u89c9\u7684\u3002\u5047\u8bbe\u79c1\u6709\u53d8\u91cf\u5728\u5e76\u884c\u533a\u57df\u524d\u9762\u5df2\u7ecf\u88ab\u58f0\u660e\uff0c\u4f46\u662f\u5728\u5e76\u884c\u533a\u57df\u5f00\u59cb\u9636\u6bb5\uff0c\u8fd9\u4e2a\u79c1\u6709\u53d8\u91cf\u503c\u53d8\u4e3a\u672a\u5b9a\u4e49\uff0c\u5728\u5e76\u884c\u533a\u57df\u7ed3\u675f\u4ee5\u540e\uff0c\u4e5f\u4f1a\u53d8\u6210\u672a\u5b9a\u4e49\u3002\u4f8b\u5982\uff1a<\/p>\n\n\n\n
int p = 0; \n\/\/ the value of p is 0\n\u200b\n#pragma omp parallel private(p)\n{\n    \/\/ the value of p is undefined\n    p = omp_get_thread_num();\n    \/\/ the value of p is defined\n    ...\n}\n\/\/ the value of p is undefined\n<\/pre>\n\n\n\n
\u6240\u4ee5\u4e3a\u4e86\u987a\u4ece\u6211\u4eec\u7684\u76f4\u89c9\uff0c\u6211\u4eec\u5c3d\u91cf\u5728\u5e76\u884c\u533a\u57df\u5185\u90e8\u5b9a\u4e49\u53d8\u91cf\u3002\u4f8b\u5982\u4e0a\u9762\u8fd9\u6bb5\u4ee3\u7801\uff0c\u6211\u4eec\u53ef\u4ee5\u53d8\u6210<\/p>\n\n\n\n
#pragma omp parallel\n{\n  int p = omp_get_thread_num();\n  ...\n}\n<\/pre>\n\n\n\n
\u8fd9\u6837\u7684\u5199\u6cd5\u4e5f\u80fd\u63d0\u9ad8\u4ee3\u7801\u53ef\u8bfb\u6027\u3002<\/p>\n\n\n\n
Default<\/h3>\n\n\n\n
default\u6709\u4e24\u4e2a\u7248\u672c\u3002\u6211\u4eec\u5148\u6765\u770b\u4e00\u4e0bdefault(shared)<\/p>\n\n\n\n
default(shared)<\/strong><\/h4>\n\n\n\n
default(shared)<\/code>\u5b50\u53e5\u5c06\u4f1a\u628a\u6240\u6709\u6d89\u53ca\u5230\u6570\u636e\u5171\u4eab\u7684\u53d8\u91cf\u8bbe\u7f6e\u4e3a\u5171\u4eab\u53d8\u91cf\u3002\u4f8b\u5982\uff1a<\/p>\n\n\n\n
int a, b, c, n;\n...\n\n#pragma omp parallel for default(shared)\nfor (int i = 0; i < n; i++)\n{\n    \/\/ using a, b, c\n}<\/pre>\n\n\n\n
<\/p>\n\n\n\n
\u8fd9\u91cca<\/code>,b<\/code>,c<\/code>,n<\/code>\u90fd\u662f\u5171\u4eab\u53d8\u91cf<\/p>\n\n\n\n
\u53e6\u5916\u4e5f\u53ef\u4ee5\u5c06\u5927\u591a\u6570\u53d8\u91cf\u9ed8\u8ba4\u4e3ashared\uff0c\u5c06\u90e8\u5206\u53d8\u91cf\u7279\u6307\u6210private\u3002<\/p>\n\n\n\n
int a, b, c, n;\n\n#pragma omp parallel for default(shared) private(a, b)\nfor (int i = 0; i < n; i++)\n{\n    \/\/ a and b are private variables\n    \/\/ c and n are shared variables \n}\t<\/pre>\n\n\n\n
Default(none)<\/strong><\/h4>\n\n\n\n
default(none)<\/code>\u5b50\u53e5\u5f3a\u5236\u7a0b\u5e8f\u5458\u6307\u5b9a\u6240\u6709\u53d8\u91cf\u7684data sharing\u5c5e\u6027\u3002<\/p>\n\n\n\n
\u4eba\u5728\u70e6\u7684\u65f6\u5019\uff0c\u53ef\u80fd\u4f1a\u778e\u5199\u51fa\u8fd9\u4e9b\u4ee3\u7801\uff1a<\/p>\n\n\n\n
int n = 10;\nstd::vector<int> vector(n);\nint a = 10;\n\n#pragma omp parallel for default(none) shared(n, vector)\nfor (int i = 0; i < n; i++)\n{\n    vector[i] = i * a;\n}<\/pre>\n\n\n\n
\u7136\u540e\u7f16\u8bd1\u5668\u5c31\u4f1a\u62a5\u9519\uff1a<\/p>\n\n\n\n
error: \u2018a\u2019 not specified in enclosing parallel
         vector[i] = i * a;
                       ^
error: enclosing parallel
     #pragma omp parallel for default(none) shared(n, vector)<\/pre>\n\n\n\n
\u7f16\u8bd1\u5668\u5403\u51fa\u8fd9\u91cca\u6ca1\u6709\u88ab\u6807\u660e\u6570\u636e\u5171\u4eab\u5c5e\u6027,\u4fee\u6539\u6210\uff1a<\/p>\n\n\n\n
int n = 10;\nstd::vector<int> vector(n);\nint a = 10;\n\n#pragma omp parallel for default(none) shared(n, vector, a)\nfor (int i = 0; i < n; i++)\n{\n    vector[i] = i * a;\n}<\/pre>\n\n\n\n
\u53ef\u4ee5\u901a\u8fc7\u7f16\u8bd1\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5199\u5728\u6700\u540e\uff1a<\/p>\n\n\n\n
\u6709\u4e24\u6761\u89c4\u5219<\/p>\n\n\n\n
    \n
  1. \u9f13\u52b1\u5927\u5bb6\u5728\u5199\u5e76\u884c\u533a\u57df\u65f6\u5019\uff0c\u4f7f\u7528default(none)\u5b50\u53e5\uff0c\u8fd9\u6837\u53ef\u4ee5\u8feb\u4f7f\u7a0b\u5e8f\u5458\u601d\u8003\u53d8\u91cf\u7684\u6570\u636e\u7c7b\u578b\u5e94\u8be5\u662f\u600e\u6837\u7684<\/li>\n\n\n\n
  2. \u5c3d\u53ef\u80fd\u5728\u5e76\u884c\u533a\u57df\u5185\u58f0\u660e\u79c1\u6709\u53d8\u91cf\uff0c\u63d0\u9ad8\u4ee3\u7801\u53ef\u8bfb\u6027\uff0c\u4f7f\u5f97\u903b\u8f91\u6e05\u6670<\/li>\n<\/ol>\n\n\n\n
    Links:<\/p>\n\n\n\n