原子最小操作的高性能工具 [英] High performance implement of atomic minimal operation

问题描述

OpenMP中没有原子的最小操作，英特尔MIC的指令集中也没有固有的最小操作.

There is no atomic minimal operation in OpenMP, also no intrinsic in Intel MIC's instruction set.

#pragmma omp critial的性能非常不足.

我想知道是否有用于Intel MIC的atomic minimal高性能工具.

I want to know if there is a high performance implement of atomic minimal for Intel MIC.

推荐答案

根据 OpenMP 4.0规范(第2.12.6节)，有很多快速的原子最小操作，您可以使用#pragma omp atomic构造代替#pragma omp critical(从而避免其锁定的巨大开销.

According to the OpenMP 4.0 Specifications (Section 2.12.6), there is a lot of fast atomic minimal operations you can do by using the #pragma omp atomic construct in place of #pragma omp critical (and thereby avoid the huge overhead of its lock).

让x作为您的线程共享变量:

Let x be your thread-shared variable:

• 使用#pragma omp atomic read，您可以自动让您的共享变量x被读取:

• With #pragma omp atomic read you can atomically let your shared variable x be read:

v = x;

使用#pragma omp atomic write，您可以为共享变量x原子分配一个新值；新值表达式(expr)必须与x无关:

With #pragma omp atomic write you can atomically assign a new value to your shared variable x; the new value expression (expr) has to be x-independant:

x = expr;

使用#pragma omp atomic update，您可以自动更新共享变量x；实际上，您只能在独立于x的表达式和x之间将新值分配为二进制运算(binop):

With #pragma omp atomic update you can atomically update your shared variable x; in fact you can only assign a new value as a binary operation (binop) between an x-independant expression and x:

x++;
x--;
++x;
--x;
x binop= expr;
x = x binop expr;
x = expr binop x;

使用#pragma omp atomic capture，您可以自动地让共享变量x读取和更新(按您想要的顺序)；实际上，capture是read和update构造的组合:

With #pragma omp atomic capture you can atomically let your shared variable x be read and updated (in the order you want); in fact capture is a combination of the read and update construct:

• 您有update然后是read的简写形式:

v = ++x;
v = --x;
v = x binop= expr;
v = x = x binop expr;
v = x = expr binop x;

和它们的结构块类似物:

And their structured-block analogs:

{--x; v = x;}
{x--; v = x;}
{++x; v = x;}
{x++; v = x;}
{x binop= expr; v = x;}
{x = x binop expr; v = x;}
{x = expr binop x; v = x;}

您可以使用read然后是update的几种缩写形式:

And you have a few short forms for read and then update:

v = x++;
v = x--;

以及它们的结构块类似物:

And again their structured-block analogs:

{v = x; x++;}
{v = x; ++x;}
{v = x; x--;}
{v = x; --x;}

最后还有另外的read和update，它们仅以结构块形式存在:

And finally you have additional read then update, which only exists in structured-block forms :

{v = x; x binop= expr;}
{v = x; x = x binop expr;}
{v = x; x = expr binop x;}
{v = x; x = expr;}

在前面的表达式中:

• x和v均为 l值表达式；
• expr是标量类型的表达式；
• binop是+，*，-，/，&，^，|，<<或>>之一;
• binop，binop=，++和--不是重载运算符.

• x and v are both l-value expressions with scalar type;
• expr is an expression with scalar type;
• binop is one of +, *, -, /, &, ^, |, << or >>;
• binop, binop=, ++ and -- are not overloaded operators.

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