#pragma omp parallel for reduction(+ : sum) for ( int i = 1; i <= 4; ++ i ) { std::cout << "thread " << omp_get_thread_num() << " sum's address is " << &sum << " value is " << sum << std::endl; sum += i; } std::cout << "After parallelism sum addr is...
在这段代码中,我们使用了“pragma omp parallel for”指令将for循环并行化。关键字“reduction”用于保证多个线程对同一个变量进行操作时的正确性。 **步骤 3:编译并运行程序** 最后,我们需要使用支持OpenMP的编译器来编译我们的程序,并在运行时指定线程数。 假设我们的文件名为“parallel_for.c”,我们可以使用以下...
-omp_get_num_threads, 返回当前并行区域中的活劢线程个数。 -omp_get_thread_num, 返回线程号 -omp_set_num_threads, 设置并行执行代码时的线程个数 omp_init_lock, 刜始化一个简单锁 omp_set_lock, 上锁操作 omp_unset_lock, 解锁操作,要和omp_set_lock函数配对使用。 omp_destroy_lock, omp_init_lo...
使用pragma omp 减少子句逼近 PICreated: November-22, 2018 int i; int n = 1000000; double area = 0; double h = 1.0 / n; #pragma omp parallel for shared(n, h) reduction(+:area) for (i = 1; i <= n; i++) { double x = h * (i - 0.5); area += (4.0 / (...
#pragma omp simd { for (i=0; i<N; i++) { a[i] = a[i] + b[i] * c[i]; } } Example 2 The loop in the following example contains a lexically forward loop-carried dependency that prohibits concurrent execution of all iterations of the loop. Theomp simd safelen(4)directive spec...
s，user 1 m46 s}在英特尔酷睿i7- 10850 H CPU上运行12个线程-与manual reduction.相同 ...
@krzakov,#pragma omp reduction(+:sum) 是不正确的。编译器很可能会忽略它,并且您会遇到一个由数值不精确性隐藏的危险数据竞争。 reduction是一个子句,它必须应用于另一个OpenMP指令 - 在您的情况下是parallel for指令。 - Hristo Iliev 1 替换: #pragma omp atomic 使用#pragma omp reduction(+:sum)或...
:对下面程序,说法正确的是 # pragma omp parallel for num_threads(thread_count) \ reduction(+:sum) for (k = 1; k <= n; k++) { sum += factor/(2*k-1); factor = -factor; } A. 利已通报细道查标走数利已通报细道查标走数破坏了数据依赖利已通报细道查标走数利已通报细道查标走数...
Variables specified in thereductionclause: must be of a type appropriate to the operator. must be shared in the enclosing context. must not be const-qualified. must not have pointer type. orderedSpecify this clause if an ordered construct is present within the dynamic extent of theomp fordirect...
for(int b=0; b<128;b++){ double myterm = (double)a*b; #pragma omp atomic S2 += myterm; } } return S2; } 问题是 #pragma omp atomic 对程序行为没有影响,即使我删除它,也没有任何反应。即使我把它改成 #pragma oh_my_god