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我有一个与 pmap 一起使用的函数来并行化它。我想每次使用 10 个工作人员异步运行 4 次此函数，但我不能同时运行两个或更多 pmap。

我在 linux 上使用 Julia v1.1 和 40-CPUs 机器。

using Distributed
addprocs(4)

@everywhere function TestParallel(x)
    a = 0
    while a < 4
        println("Value = ",x, " in worker = ", myid())
        sleep(1)
        a += 1
    end
end

a = WorkerPool([2,3])
b = WorkerPool([4,5])

c = [i for i = 1:10]
@sync @async for i in c
    pmap(x-> TestParallel(x), a, c)
    pmap(x-> TestParallel(x), b, c)
end

我希望有：

From worker 2:    Value = 1 in worker = 2
From worker 3:    Value = 2 in worker = 3
From worker 4:    Value = 3 in worker = 4
From worker 5:    Value = 4 in worker = 5

因此，c 的前两个元素进入第一个 pmap，接下来的两个元素进入第二个 pmap，然后谁先完成，就会得到接下来的两个元素。

现在我得到：

 From worker 2:    Value = 1 in worker = 2
 From worker 3:    Value = 2 in worker = 3
 From worker 2:    Value = 1 in worker = 2
 From worker 3:    Value = 2 in worker = 3

在第一个 pmap 完成 c 的所有元素后，第二个 pmap 重新开始求解所有元素。

From worker 2:    Value = 9 in worker = 2
From worker 3:    Value = 10 in worker = 3
From worker 5:    Value = 2 in worker = 5
From worker 4:    Value = 1 in worker = 4
4

1 回答 1

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您的问题存在一些问题：使用绿色线程@sync并且@async您想要分配计算。语法@sync @async [some code]异步生成代码并等待它完成。因此实际上它与 具有相同的含义[some code]。

虽然您的问题尚不清楚，但我会假设您希望pmap使用单独的工作池并行启动 2 s（这似乎是您最有可能尝试做的事情）。

在这种情况下，这里是代码：

using Distributed
addprocs(4)

@everywhere function testpar2(x)
    for a in 0:3
        println("Value = $x [$a] in worker = $(myid())")
        sleep(0.2)
    end
    return 1000*myid()+x*x  #I assume you want to return some value
end


a = WorkerPool([2,3])
b = WorkerPool([4,5])

c = collect(1:10)

@sync begin
    @async begin 
        res1 = pmap(x-> testpar2(x), a, c)
        println("Got res1=$res1")
    end
    @async begin 
        res2 = pmap(x-> testpar2(x), b, c)
        println("Got res2=$res2")
    end
end

运行上述代码时，您将看到如下内容：

...
      From worker 5:    Value = 10 [3] in worker = 5
      From worker 2:    Value = 10 [3] in worker = 2
      From worker 3:    Value = 9 [3] in worker = 3
Got res2=[4001, 5004, 5009, 4016, 5025, 4036, 4049, 5064, 4081, 5100]
Got res1=[2001, 3004, 2009, 3016, 2025, 3036, 3049, 2064, 3081, 2100]
Task (done) @0x00000000134076b0

您可以清楚地看到，两个 pmap 都在不同的工作池上并行运行。

于 2019-08-12T17:18:16.250 回答