英文:
Is there a simple `parallel for` in golang like OpenMP?
问题
我正在尝试使用并行处理来优化一个谜题，以提高性能。
理想情况下，在C99中使用OpenMP，我应该能够在相关的for循环之前使用#pragma omp parallel for来实现并行处理，然后系统会自动在CPU之间分配负载。
然而，Go的官方文档（https://golang.org/doc/effective_go.html#parallel）似乎暗示了为了进行并行处理，我必须：（0）手动从运行时环境获取核心数，（1）循环遍历这些核心，（2）为每个核心编写一个独立的for循环，（3）再次循环遍历这些核心以确保所有的内容都被处理。
我是否漏掉了什么？对于最简单的情况来说，使用古老的C和OpenMP是否比被宣传为C的最佳替代品的全新Go更好？对于更复杂的例子，如何将一个range分割给多个CPU处理？
英文:
I'm trying to optimise a puzzle with parallel processing, for better performance.
Ideally, in C99 w/ OpenMP, I should be able to do that with the help of a #pragma omp parallel for prior to a for loop in question, and then it should be up to the system to distribute the load between the CPUs.
The official documentation for Go at https://golang.org/doc/effective_go.html#parallel, however, seems to suggest that for parallel processing I must, (0), manually get the number of cores from the runtime environment, (1), loop over said cores, (2), effectively code up a distinct for loop for each core, (3), loop over the cores once again to make sure all the stuff got processed.
Am I missing something? For the simplest case, is OpenMP with the ancient C superior to the brand new Go that's touted as C's best replacement? For a more complicated example, how exactly do you split up a range between the CPUs?
答案1
得分: 6
Effective Go在这方面已经过时了，Go会自动将GOMAXPROCS设置为处理器的数量（你仍然可以手动设置它来强制使用你想要的数量）。
这里有一个非常简单的并行处理切片的示例：
data := make([]float64, SZ)
var wg sync.WaitGroup
for i := range data {
wg.Add(1)
go func(v *float64) {
// 注意，使用rand是一个不好的示例，因为全局rand使用了互斥锁
*v = rand.Float64()
wg.Done()
}(&data[i])
}
wg.Wait()
英文:
Effective Go is outdated about that, Go automatically sets GOMAXPROCS to the number of processors (you can still manually set it to force the number you want).
Here's a very simple example for parallel processing of a slice:
data := make([]float64, SZ)
var wg sync.WaitGroup
for i := range data {
wg.Add(1)
go func(v *float64) {
// note that using rand is a bad example because global rand uses a mutex
*v = rand.Float64()
wg.Done()
}(&data[i])
}
wg.Wait()
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