{"id":4496,"date":"2018-04-03T17:53:04","date_gmt":"2018-04-03T08:53:04","guid":{"rendered":"https:\/\/blog.bitmeister.jp\/?p=4496"},"modified":"2018-04-09T18:49:48","modified_gmt":"2018-04-09T09:49:48","slug":"%e3%82%b9%e3%83%ac%e3%83%83%e3%83%89%e9%96%93%e3%81%a7%e3%82%ab%e3%82%a6%e3%83%b3%e3%82%bf%e3%82%92%e5%85%b1%e6%9c%89%e3%81%99%e3%82%8b","status":"publish","type":"post","link":"https:\/\/blog.bitmeister.jp\/?p=4496","title":{"rendered":"\u30b9\u30ec\u30c3\u30c9\u9593\u3067\u30ab\u30a6\u30f3\u30bf\u3092\u5171\u6709\u3059\u308b"},"content":{"rendered":"

C\u8a00\u8a9e\u3067\u306f\u3001\u8907\u6570\u306e\u30b9\u30ec\u30c3\u30c9\u304c\u5171\u6709\u3059\u308b\u5909\u6570\u3092\u5358\u7d14\u306b\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3059\u308b\u3068\u671f\u5f85\u901a\u308a\u306e\u7d50\u679c\u306b\u306a\u308a\u307e\u305b\u3093\u3002\u3042\u308b\u3044\u306f\u7c21\u5358\u306a\u30c6\u30b9\u30c8\u3067\u3046\u307e\u304f\u52d5\u3044\u305f\u3068\u3057\u3066\u3082\u3001\u9ad8\u8ca0\u8377\u306b\u306a\u308b\u3068\u304a\u304b\u3057\u306a\u7d50\u679c\u3092\u8fd4\u3057\u307e\u3059\u3002\u3053\u306e\u624b\u306e\u30d0\u30b0\u306f\u518d\u73fe\u6761\u4ef6\u3092\u63c3\u3048\u308b\u3053\u3068\u81ea\u4f53\u304c\u96e3\u3057\u3044\u306e\u3067\u3001\u306f\u3058\u3081\u304b\u3089\u5b89\u5168\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u3051\u308b\u3088\u3046\u306b\u6319\u52d5\u3092\u77e5\u3063\u3066\u304a\u304f\u3053\u3068\u304c\u5927\u4e8b\u3067\u3059\u3002<\/p>\n

<\/p>\n

\u307e\u305a\u3046\u307e\u304f\u3044\u304b\u306a\u3044\u30b5\u30f3\u30d7\u30eb\u30b3\u30fc\u30c9\u304c\u3053\u3061\u3089\u300210\u500b\u306e\u30b9\u30ec\u30c3\u30c9\u3092\u8d77\u3053\u3057\u3066\u3001\u305d\u308c\u305e\u308c\u306e\u30b9\u30ec\u30c3\u30c9\u304c\u5171\u6709\u5909\u6570\u3092\u30ca\u30a4\u30fc\u30d6\u306b100\u4e07\u56de\u30ab\u30a6\u30f3\u30c8\u30a2\u30c3\u30d7\u3057\u307e\u3059\u3002<\/p>\n

\r\n#include <stdio.h>\r\n#include <pthread.h>\r\n\r\nvoid *func(void *i) {\r\n    int j;\r\n\r\n    for (j = 0; j < 1000000; j++)\r\n        (*(int *)i)++;  \/\/ <- counts up\r\n\r\n    return NULL;\r\n}\r\n\r\nint main() {\r\n    int n = 0, x = 0;\r\n    pthread_t th[10];\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_create(&th[n], NULL, func, &x);\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_join(th[n], NULL);\r\n\r\n    printf("%d\\n", x); \r\n\r\n    return 0;\r\n}\r\n<\/pre>\n
\u3059\u308b\u3068\u3001\u3053\u3093\u306a\u7d50\u679c\u304c\u8fd4\u308a\u307e\u3059\u3002\uff08\u3042\u3068\u3067\u6027\u80fd\u306b\u3064\u3044\u3066\u3082\u8003\u3048\u308b\u306e\u3067\u3001time\u30b3\u30de\u30f3\u30c9\u3092\u565b\u307e\u305b\u307e\u3059\u3002\uff09<\/p>\n
\r\n$ time .\/a.out\r\n2871703\r\n\r\nreal\t0m0.037s\r\nuser\t0m0.207s\r\nsys\t0m0.000s\r\n<\/pre>\n
\u671f\u5f85\u3059\u308b\u7d50\u679c1000\u4e07(10\u30b9\u30ec\u30c3\u30c9*100\u4e07\u56de\u30ab\u30a6\u30f3\u30c8\u30a2\u30c3\u30d7)\u306b\u6bd4\u3079\u3066\u3001\u51fa\u529b\u3055\u308c\u305f\u5024\u306f\u9065\u304b\u306b\u5c11\u306a\u3044\u3067\u3059\u3002\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u306fC\u3067\u306f1\u884c\u3067\u6e08\u3080\u306e\u3067\u30a2\u30c8\u30df\u30c3\u30af\uff08\u4e0d\u53ef\u5206\uff09\u306a\u51e6\u7406\u306b\u601d\u3044\u304c\u3061\u3067\u3059\u304c\u3001Read-Modify-Write\u3068\u3044\u30463\u3064\u306e\u51e6\u7406\u306b\u5206\u3051\u3066\u5b9f\u884c\u3055\u308c\u308b\u306e\u304c\u666e\u901a\u3067\u3059\u3002<\/p>\n
    \n
  1. \u30e1\u30e2\u30ea\u304b\u3089\u30ec\u30b8\u30b9\u30bf\u306b\u8aad\u307f\u8fbc\u307f<\/li>\n
  2. \u30ec\u30b8\u30b9\u30bf\u306b\u5165\u308c\u305f\u5024\u306b\u5bfe\u3057\u3066\u547d\u4ee4\u3055\u308c\u305f\u6f14\u7b97\u3092\u884c\u3046<\/li>\n
  3. \u7d50\u679c\u306e\u5165\u3063\u305f\u30ec\u30b8\u30b9\u30bf\u306e\u5024\u3092\u30e1\u30e2\u30ea\u306b\u66f8\u304d\u8fbc\u3080<\/li>\n<\/ol>\n
    \u3068\u3044\u3046\u6d41\u308c\u306e\u51e6\u7406\u3067\u3059\u3002\u3053\u3093\u306a\u611f\u3058\u3002<\/p>\n
    \r\nread a\r\n>------+\r\n       |\r\n       * modify a\r\nwrite a|\r\n<------+\r\n\r\nread b\r\n>------+\r\n       |\r\n       * modify b\r\nwrite b|\r\n<------+\r\n<\/pre>\n
    \u3053\u306e\u6d41\u308c\u306b\u5247\u3063\u3066\u51e6\u7406\u3055\u308c\u3066\u3044\u308c\u3070\u554f\u984c\u306a\u3044\u306e\u3067\u3059\u304c\u3001\u30e1\u30e2\u30ea\u30a2\u30af\u30bb\u30b9\u306f\u975e\u5e38\u306b\u6642\u9593\u304c\u304b\u304b\u308b\u30cf\u30a4\u30b3\u30b9\u30c8\u306a\u64cd\u4f5c\u306a\u306e\u3067\u3001\u30de\u30eb\u30c1\u30b9\u30ec\u30c3\u30c9\u3060\u3068\u6b21\u306e\u3088\u3046\u306a\u30ec\u30fc\u30b9\u30b3\u30f3\u30c7\u30a3\u30b7\u30e7\u30f3(\u7af6\u5408\u72b6\u614b)\u304c\u983b\u767a\u3057\u307e\u3059\u3002\u305f\u3068\u3048\u3070\u3001\u30af\u30ed\u30b9\u30aa\u30fc\u30d0\u30fc\u3002<\/p>\n
    \r\nread a\r\n>------+\r\n       |\r\n       |\r\n       * modify a\r\nread b |\r\n>-----------+\r\n       |    |\r\n       |    |\r\nwrite a|    * modify b\r\n<-------    |\r\n            |\r\nwrite b     |\r\n<-----------+\r\n<\/pre>\n
    \u3042\u308b\u3044\u306f\u3001\u30aa\u30fc\u30d0\u30fc\u30e9\u30c3\u30d7\u3002<\/p>\n
    \r\nread a\r\n>-----------+\r\n            |\r\nread b      * modify a\r\n>------+    |\r\n       |    |\r\n       * modify b\r\n       |    |\r\nwrite b|    |\r\n<-------    |\r\n            |\r\nread c      |\r\n>------+    |\r\n       |    |\r\n       * modify c\r\n       |    |\r\nwrite c|    |\r\n<-------    |\r\n            |\r\nwrite a     |\r\n<-----------+\r\n<\/pre>\n
    \u3053\u306e\u3088\u3046\u306b\u51e6\u7406\u304c\u5272\u308a\u8fbc\u307e\u308c\u308b\u3068\u3001\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u306b\u5931\u6557\u3057\u307e\u3059\u3002\u5bfe\u51e6\u3068\u3057\u3066\u305f\u307e\u306b\u898b\u304b\u3051\u308b\u8aa4\u3063\u305f\u4f8b\u306f\u3001\u5171\u6709\u3055\u308c\u308b\u5909\u6570\u306e\u5ba3\u8a00\u306bvolatile\u4fee\u98fe\u5b50\u3092\u4ed8\u3051\u308b\u3068\u3044\u3046\u3082\u306e\u3067\u3059\u3002<\/p>\n
    \r\n#include <stdio.h>\r\n#include <pthread.h>\r\n\r\nvolatile int i = 0;\r\n\r\nvoid *func() {\r\n    int j;\r\n\r\n    for (j = 0; j < 1000000; j++)\r\n        i++;\r\n\r\n    return NULL;\r\n}\r\n\r\nint main() {\r\n    int n = 0;\r\n    pthread_t th[10];\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_create(&th[n], NULL, func, NULL);\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_join(th[n], NULL);\r\n\r\n    printf("%d\\n", i); \r\n\r\n    return 0;\r\n}\r\n<\/pre>\n
    C\u8a00\u8a9e\u3067\u306fvolatile\u4fee\u98fe\u5b50\u306e\u5f79\u5272\u306f\u30b3\u30f3\u30d1\u30a4\u30e9\u306e\u6700\u9069\u5316\u3092\u6291\u6b62\u3059\u308b\u3053\u3068\u3067\u3059\u3002\u305f\u3068\u3048\u3070\u3001\u30e1\u30e2\u30ea\u30de\u30c3\u30d7\u30c8I\/O\u306e\u3088\u3046\u306a\u5510\u7a81\u306b\u7279\u5b9a\u306e\u30a2\u30c9\u30ec\u30b9\u3078\u66f8\u304d\u8fbc\u307f\u3092\u884c\u3046\u3088\u3046\u306a\u30b3\u30fc\u30c9\u3092\u30b3\u30f3\u30d1\u30a4\u30e9\u304c\u4e0d\u8981\u3068\u307f\u306a\u3057\u3066\u52dd\u624b\u306b\u6d88\u3057\u3066\u3057\u307e\u3046\u3053\u3068\u3092\u6291\u6b62\u3059\u308b\u3088\u3046\u306a\u7528\u9014\u306b\u4f7f\u3044\u307e\u3059\u3002\u4fee\u98fe\u3055\u308c\u305f\u5909\u6570\u3078\u306e\u51e6\u7406\u304c\u30b9\u30ec\u30c3\u30c9\u5b89\u5168\u306b\u306a\u308b\u308f\u3051\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u3002\u3080\u3057\u308d\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u30fb\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3067\u306f\u307b\u3068\u3093\u3069\u306a\u306b\u3082\u4fdd\u8a3c\u3057\u3066\u304f\u308c\u306a\u3044\u3068\u601d\u3063\u305f\u307b\u3046\u304c\u3044\u3044\u3067\u3059\u3002\u3070\u3063\u3061\u308a\u5272\u308a\u8fbc\u307e\u308c\u307e\u3059\u3002(POS03-C. volatile \u3092\u540c\u671f\u7528\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u3068\u3057\u3066\u4f7f\u7528\u3057\u306a\u3044)<\/a><\/p>\n
    $ time .\/a.out \r\n2546514\r\n\r\nreal\t0m0.040s\r\nuser\t0m0.225s\r\nsys\t0m0.000s\r\n<\/pre>\n
    \u89e3\u6c7a\u3068\u3057\u3066\u4e00\u822c\u7684\u306a\u65b9\u6cd5\u306fmutex(MUTual EXclusion)\u3092\u4f7f\u3063\u3066\u8907\u6570\u306e\u30b9\u30ec\u30c3\u30c9\u304c\u540c\u6642\u306b\u30af\u30ea\u30c6\u30a3\u30ab\u30eb\u30bb\u30af\u30b7\u30e7\u30f3\u3078\u5165\u308b\u3053\u3068\u3092\u9632\u3050\u3068\u3044\u3046\u3082\u306e\u3067\u3059\u3002<\/p>\n
    #include <stdio.h>\r\n#include <stdatomic.h>\r\n#include <pthread.h>\r\n\r\n\r\nstruct params {\r\n    int *i; \r\n    pthread_mutex_t *mut;\r\n};\r\n\r\nvoid *func(void *arg) {\r\n    int j;\r\n    struct params *prm = (struct params *) arg;\r\n\r\n    for (j = 0; j < 1000000; j++) {\r\n        pthread_mutex_lock(prm->mut);\r\n        (*(int *)prm->i)++;\r\n        pthread_mutex_unlock(prm->mut);\r\n    }   \r\n\r\n    return NULL;\r\n}\r\n\r\nint main() {\r\n    int n = 0, x = 0;\r\n    pthread_t th[10];\r\n    pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;\r\n    struct params prm = {&x, &mut};\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_create(&th[n], NULL, func, &prm);\r\n\r\n    for (n = 0; n < 10; n++)\r\n        pthread_join(th[n], NULL);\r\n\r\n    printf("%d\\n", x); \r\n\r\n    return 0;\r\n}\r\n<\/pre>\n
    \u3053\u308c\u3067\u671f\u5f85\u901a\u308a\u306e\u7d50\u679c\u3092\u5f97\u3089\u308c\u307e\u3059\u3002<\/p>\n
    \r\n$ time .\/a.out \r\n10000000\r\n\r\nreal\t0m2.117s\r\nuser\t0m1.272s\r\nsys\t0m14.747s\r\n<\/pre>\n
    \u554f\u984c\u306f\u3001mutex\u306f\u975e\u5e38\u306b\u30b3\u30b9\u30c8\u304c\u304b\u304b\u308b\u3068\u3044\u3046\u3053\u3068\u3067\u3059\u30021000\u4e07\u56de\u306e\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u306b\u5b9f\u6642\u9593\u30672\u79d2\u4ee5\u4e0a\u304b\u304b\u308a\u3001CPU\u6642\u9593\u3067\u306f16\u79d2\u3082\u304b\u304b\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n
    \u6b21\u56de<\/a>\u306f\u3053\u306e\u6027\u80fd\u52a3\u5316\u306b\u3064\u3044\u3066\u8003\u3048\u3066\u307f\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
    C\u8a00\u8a9e\u3067\u306f\u3001\u8907\u6570\u306e\u30b9\u30ec\u30c3\u30c9\u304c\u5171\u6709\u3059\u308b\u5909\u6570\u3092\u5358\u7d14\u306b\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3059\u308b\u3068\u671f\u5f85\u901a\u308a\u306e\u7d50\u679c\u306b\u306a\u308a\u307e\u305b\u3093\u3002\u3042\u308b\u3044\u306f\u7c21\u5358\u306a\u30c6\u30b9\u30c8\u3067\u3046\u307e\u304f\u52d5\u3044\u305f\u3068\u3057\u3066\u3082\u3001\u9ad8\u8ca0\u8377\u306b\u306a\u308b\u3068\u304a\u304b\u3057\u306a\u7d50\u679c\u3092\u8fd4\u3057\u307e\u3059\u3002\u3053\u306e\u624b\u306e\u30d0\u30b0\u306f\u518d\u73fe\u6761\u4ef6\u3092\u63c3\u3048\u308b\u3053\u3068\u81ea\u4f53\u304c\u96e3 […]<\/p>\n","protected":false},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-4496","post","type-post","status-publish","format-standard","hentry","category-tech"],"_links":{"self":[{"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/posts\/4496","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4496"}],"version-history":[{"count":33,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/posts\/4496\/revisions"}],"predecessor-version":[{"id":4562,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=\/wp\/v2\/posts\/4496\/revisions\/4562"}],"wp:attachment":[{"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4496"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4496"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.bitmeister.jp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4496"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}