Question

我试图运行看起来像这样的东西：

y = @parallel (min) for i in collection
    f(i)
end

其中f(i)是一个基本上是while循环的函数，它计算完成条件所需的迭代次数。开始时，终止条件之一是预定的迭代次数n。但是，如果f(i)的回报率低于n，那么理想情况下，我希望将n替换为f(i)的值（例如，因为我正在寻找最小值f(i) 1}}，如果f(j)为m，我希望所有其他循环停止检查它们是否达到m次迭代）。

我对并行计算很陌生，所以我可能会误解documentation，但我认为我应该可以这样做：

x = Channel{Int64}(1)
put!(x,n)

y = @parallel (min) for i in collection
    f(i,x)
end

close(x)

我已修改f以获取Channel参数，现在它看起来像这样：

@everywhere function f(item,chan)
    going = true
    count = 0
    while (going)
        going = false
        # perform some operations
        if (count < fetch(chan) && !conditions_met())
            # conditions_met checks the other termination conditions
            going = true
            count += 1
        end
    end

    count += 1

    if (count < fetch(chan))
        take!(chan)
        put!(chan,count)
    end

    return count
end

如果我将第一个count < fetch(chan)替换为count < n并删除其他if阻止/ Channel代码，则脚本运行正常。但是，由于n将比最小f(i)大几个数量级，如果我可以像我所描述的那样做，它会显着加快计算速度。这是我应该做的事情，如果是这样，我是否正确接近这个？

现在我遇到以下错误（运行4次触发）：

ERROR (unhandled task failure): On worker 3:
cannot resize array with shared data
 in shift! at array.jl:501
 in take! at channels.jl:54
 in f at /home/michael/Documents/julia/script.jl:98
 [inlined code] from /home/michael/Documents/julia/script.jl:126
 in anonymous at no file:0
 in anonymous at multi.jl:913
 in run_work_thunk at multi.jl:651
 [inlined code] from multi.jl:913
 in anonymous at task.jl:63
 in remotecall_fetch at multi.jl:737
 in remotecall_fetch at multi.jl:740
 in anonymous at multi.jl:1519
ERROR: LoadError: On worker 2:
cannot resize array with shared data
 in shift! at array.jl:501
 in take! at channels.jl:54
 in f at /home/michael/Documents/julia/script.jl:98
 [inlined code] from /home/michael/Documents/julia/script.jl:126
 in anonymous at no file:0
 in anonymous at multi.jl:913
 in run_work_thunk at multi.jl:651
 [inlined code] from multi.jl:913
 in anonymous at task.jl:63
 in preduce at multi.jl:1523
 [inlined code] from multi.jl:1532
 in anonymous at expr.jl:113
 [inlined code] from /home/michael/Documents/julia/script.jl:125
 in anonymous at no file:0
while loading /home/michael/Documents/julia/script.jl, in expression starting on line 121
ERROR (unhandled task failure): On worker 4:
cannot resize array with shared data
 in shift! at array.jl:501
 in take! at channels.jl:54
 in f at /home/michael/Documents/julia/script.jl:98
 [inlined code] from /home/michael/Documents/julia/script.jl:126
 in anonymous at no file:0
 in anonymous at multi.jl:913
 in run_work_thunk at multi.jl:651
 [inlined code] from multi.jl:913
 in anonymous at task.jl:63
 in remotecall_fetch at multi.jl:737
 in remotecall_fetch at multi.jl:740
 in anonymous at multi.jl:1519
ERROR (unhandled task failure): On worker 5:
cannot resize array with shared data
 in shift! at array.jl:501
 in take! at channels.jl:54
 in f at /home/michael/Documents/julia/script.jl:98
 [inlined code] from /home/michael/Documents/julia/script.jl:126
 in anonymous at no file:0
 in anonymous at multi.jl:913
 in run_work_thunk at multi.jl:651
 [inlined code] from multi.jl:913
 in anonymous at task.jl:63
 in remotecall_fetch at multi.jl:737
 in remotecall_fetch at multi.jl:740
 in anonymous at multi.jl:1519

其中，行98是函数定义中的take!(chan)语句，而行126中的行f(i,x)是并行for循环中的public class arrayTest { public static void main(String[] args){ Integer[] list1 = {12, 43, 56, 72}; Double[] list2 = {12.5, 45.6, 62.4, 65.8}; String[] list3 = {"1", "2", "3"}; printArray(list1); printArray(list2); printArray(list3); } public static void printArray(Object[] list){ Object o = list; System.out.println(o); }。

Answer 1

Channel为异步通信实现类似CSP的语义，但它们没有跨并行进程共享的自动机制。您出于此目的需要使用RemoteRef：http://docs.julialang.org/en/release-0.4/manual/parallel-computing/#remoterefs-and-abstractchannels

服用的功能！并把！和朱莉娅的频道

1 个答案: