R-optim调用foreach％dopar％内部函数的问题 [英] R - problem with foreach %dopar% inside function called by optim

问题描述

从optim调用包含foreach％dopar％构造的函数会导致错误:

Calling a function that includes foreach %dopar% construct from optim causes an error:

> workers <- startWorkers(6) # 6 cores
> 
> registerDoSMP(workers)
> 
> t0 <- Sys.time() 
>
> optim(w,maxProb2,control=list(fnscale=-1))
> 
> Error in { : task 1 failed - "unused argument(s) (isPrebuilt = TRUE)"
> 
> Sys.time()-t0
>
> Time difference of 2.032 secs
> 
> stopWorkers(workers)

被调用函数如下:

> maxProb2 <- function(wp) {
>   
>   r <- foreach (i=s0:s1, .combine=c) %dopar% { pf(i,x[i,5],wp,isPrebuilt=TRUE) }
>   
>   cat("w=",wp,"max=",sum(r),"\n")
>   
>   sum(r)
>   
> }

pf是其​​他函数，x是预先计算的元素的静态表.

pf is some other function, x is a static table of pre-computed elements.

也仅一次调用要优化的函数会导致相同的错误:

Also calling the function to be optimized just once causes the same error:

> workers <- startWorkers(6) # 6 cores
>
> Warning message:
> In startWorkers(6) : there is an existing doSMP session using doSMP1
>
> registerDoSMP(workers)
>
> maxProb2(w)
> Error in { : task 1 failed - "unused argument(s) (isPrebuilt = TRUE)"
>
> stopWorkers(workers)

奇怪的是，一次直接调用相同的代码就可以正常工作(optim多次调用同一函数):

What's strange, the identical code works fine when called directly a single time (optim calles the same function many times):

> workers <- startWorkers(6) # 6 - ilosc rdzeni
> 
> Warning message:
> In startWorkers(6) : there is an existing doSMP session using doSMP1
>
> registerDoSMP(workers)
> 
> r <- foreach (i=s0:s1, .combine=c) %dopar% { pf(i,x[i,5],w,isPrebuilt=TRUE) } 
>   
> sum(r)
> [1] 187.1781
> 
> stopWorkers(workers)

使用％do％代替％dopar％时，调用的函数(maxProb2)可以正常工作.

The called function (maxProb2) works fine, when %do% is used instead of %dopar%.

如何正确调用包含foreach％dopar％构造的函数?

更新2011-07-17:

UPDATE 2011-07-17:

我已将pf函数重命名为probf，但问题仍然存在.

I have renamed the pf function into probf but the problem remains.

probf函数是在脚本中定义的，而不是在某些外部程序包中定义的.

probf functions is defined in the script, not in some external package.

两个注意事项:操作系统:Windows 7，IDE:Revolution Analytics Enterprise 4.3

Two notes: OS: Windows 7, IDE: Revolution Analytics Enterprise 4.3

> workers <- startWorkers(workerCount = 3)
>
> registerDoSMP(workers)
>
> maxProb2(w)
>
Error in { : task 1 failed - "could not find function "probf""

推荐答案

我遇到了同样的问题，即子线程中未包含环境.您的错误

I ran into the same problem an the issue is with the environment not being included in the sub-threads. Your error

{中的错误:任务1失败-找不到函数"simple_fn""

Error in { : task 1 failed - "could not find function "simple_fn""

可以通过以下非常简单的示例进行复制:

can be reproduced by this very simple example:

simple_fn <- function(x)
    x+1

test_par <- function(){
    library("parallel")
    no_cores <- detectCores()
    library("foreach")
    cl<-makeCluster(no_cores)
    library("doSNOW")
    registerDoSNOW(cl)
    out <- foreach(i=1:10) %dopar% {
        simple_fn(i)
    }

    stopCluster(cl)
    return(out)
}

test_par()

现在您要做的就是将foreach(i=1:10)更改为foreach(i=1:10, .export=c("simple_fn")).如果要导出完整的全局环境，则只需编写.export=ls(envir=globalenv())，无论情况好坏，我们都会使用它.

Now all you need to to is to change the foreach(i=1:10) into foreach(i=1:10, .export=c("simple_fn")). If you want to export your complete global environment then just write .export=ls(envir=globalenv()) and you will have it for better or worse.

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