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Subject: Re: [OMPI users] testsome returns negative indices
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2014-03-21 13:02:46


So just to be clear, the C interface for MPI_Testsome is:

int MPI_Testsome(int incount, MPI_Request requests[],
                 int *outcount, int indices[],
                 MPI_Status statuses[]);

And your R call is:

       mpi_errhandler(MPI_Testsome(countn, request, &INTEGER(indices)[0],
               &INTEGER(indices)[1], status));

I'm assuming request is an MPI_Request object. And integer(indices)[0] is where you want the outcount to go, and then integer(indices)[1] through [value_of_outcount] is where you want the indices to go, right?

If so, then yes, that looks proper.

You'll probably need to look into what's happening in the R wrapper as to why you're not getting the right answers, sorry.

(and yes, the values in the indices[] array should be between 0 and (incount-1))

On Mar 21, 2014, at 12:01 PM, Ross Boylan <ross_at_[hidden]> wrote:

> On Fri, 2014-03-21 at 14:11 +0000, Jeff Squyres (jsquyres) wrote:
>> Is that C or R code?
> C.
>>
>> If it's R, I think the next step would be to check the R wrapper for MPI_Testsome and see what is actually being returned by OMPI in C before it gets converted to R. I'm afraid I don't know R, so I can't really comment on the syntax / correctness of your code snipit.
>>
>> If it's C -- which I don't think it is, but it *could* be...? -- I would need to understand your syntax in calling MPI_Testsome better; e.g., what's &INTEGER(foo)[x]?
> allocVector(INTSXP, countn+1) allocates an R vector of integers.
> INTEGER(indices) returns the data portion of that structure, where the
> actual integers go. The &...[0] get the address of the first location.
> PROTECT keeps things from being garbage-collected by R.
>
> The allocation of indices is a cheat: the first location is used for the
> outcount, and the following locations get the actual indices.
>
> status is a pointer to an array of MPI status objects,
>
> The indices should be small integers, shouldn't they? I'm also getting
> some large values back.
>
> Ross
>>
>> On Mar 20, 2014, at 8:39 PM, Ross Boylan <ross_at_[hidden]> wrote:
>>
>>> MPI_Testsome seems to have returned successfully, with a positive outcount, and yet given me a negative index, -4432. Can anyone help me understand what's going on?
>>>
>>> The call is from R, and so there might be a translation issue. My first thought was that it might be 32 vs 64 bit integers, but both OMPI and R seem to be using the C int type for the integers.
>>>
>>> Here's the inner call:
>>>
>>> SEXP mpi_testsome(SEXP sexp_count){
>>> int countn=INTEGER(sexp_count)[0];
>>> SEXP indices;
>>> PROTECT (indices = allocVector(INTSXP, countn+1));
>>> mpi_errhandler(MPI_Testsome(countn, request, &INTEGER(indices)[0],
>>> &INTEGER(indices)[1], status));
>>> UNPROTECT(1);
>>> return indices;
>>> }
>>>
>>> SEXP is an R structure.
>>>
>>> OMPI 1.7.4.
>>>
>>> Ross Boylan
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users

-- 
Jeff Squyres
jsquyres_at_[hidden]
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