R help - Feb 2015 - Parallel Computing in R

I usually need to compute P-values as following:
 1. generate one sample (usually it is a matrix)
 2. apply several methods (I already wrote a subfunction for each method,
and they are independent) to the generated sample to get pvalues.
 3. compare the pvalues.
Since each method mentioned above takes long time (always different length
of time) to compute the pvalue, I am try to computing the pvalues parallel.
I want to assign computation of each method to each cores (I have intel
i7). Do you have any suggestion? I put the four subfunctions together as

    main.fun=function(i,x,y,numper)
    {
    if (i==1) z=cca1(y,x,numper)
    if (i==2) z=2
    if (i==3) z=2
    if (i==4) z=3
    z
    }

Each i indicates ith subfunction.
But I always get

     task 1 failed - "Lapack routine dgesv: system is exactly singular:
U[84,84] = 0"

But when I only run `cca1` function (not using `foreach`), there is no
error.
The `foreach` is like this

   
pvalue=foreach(i=1:4,.combine=c,.packages=c("MASS","base"))
%dopar%
main.fun(i,x,y,500)

The single computation is like this

    pvalue=cca1(y,x,500)

I also put following in the top lines of my program

    library(foreach)
    library(doSNOW)
    library(MASS)
    cl=makeCluster(4,type="SOCK")
    registerDoSNOW(cl)

**This looks like when I compute the `pvalue` separately not using
`foreach`, there is no error. But when I combine the subfuntions togeter
like `main.fun`, it has error.**

	[[alternative HTML version deleted]]

Hi,

You already asked this here
(http://stackoverflow.com/questions/28357210/parallel-computing-in-r)
and got some comments.

Regards,
Pascal

On Fri, Feb 6, 2015 at 11:58 AM, Zhenchuan Wang <zwang10 at mtu.edu>
wrote:
> I usually need to compute P-values as following:
>  1. generate one sample (usually it is a matrix)
>  2. apply several methods (I already wrote a subfunction for each method,
> and they are independent) to the generated sample to get pvalues.
>  3. compare the pvalues.
> Since each method mentioned above takes long time (always different length
> of time) to compute the pvalue, I am try to computing the pvalues parallel.
> I want to assign computation of each method to each cores (I have intel
> i7). Do you have any suggestion? I put the four subfunctions together as
>
>     main.fun=function(i,x,y,numper)
>     {
>     if (i==1) z=cca1(y,x,numper)
>     if (i==2) z=2
>     if (i==3) z=2
>     if (i==4) z=3
>     z
>     }
>
> Each i indicates ith subfunction.
> But I always get
>
>      task 1 failed - "Lapack routine dgesv: system is exactly
singular:
> U[84,84] = 0"
>
> But when I only run `cca1` function (not using `foreach`), there is no
> error.
> The `foreach` is like this
>
>    
pvalue=foreach(i=1:4,.combine=c,.packages=c("MASS","base"))
%dopar%
> main.fun(i,x,y,500)
>
> The single computation is like this
>
>     pvalue=cca1(y,x,500)
>
> I also put following in the top lines of my program
>
>     library(foreach)
>     library(doSNOW)
>     library(MASS)
>     cl=makeCluster(4,type="SOCK")
>     registerDoSNOW(cl)
>
> **This looks like when I compute the `pvalue` separately not using
> `foreach`, there is no error. But when I combine the subfuntions togeter
> like `main.fun`, it has error.**
>
>         [[alternative HTML version deleted]]
>
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