[R] Rmpi and C Code, where to get the communicator

[Martin Morgan]

Hi Markus --

Usually comm is an argument with default value in the mpi.* functions, 
so implicitly the user is managing these, e.g., by default, using comm 
1. Presumably you'll have an R wrapper to .Call that has a default 
argument comm=1, and will passs this to the C level.

Martin

Markus Schmidberger wrote:
> Hello,
> 
> I try to write parts of my code in C to accelerate the for-loops. But 
> basic operations I want to do in R (e.g. start cluster). My R code looks 
> something like this:
> 
> library(Rmpi)
> mpi.spawn.Rslaves()
> mpi.remote.exec(....)
> dyn.load("test.so")
> erg <- .Call("test", ....)
> ....
> mpi.close.Rslaves()
> mpi.quit()
> 
> And my C function looks something like this:
> 
> #include <mpi.h>
> #include <R.h>
> #include <Rdefines.h>
> #include <Rinternals.h>
> SEXP test (SEXP a, ..){
>    int rank;
>    comm ??????
>    MPI_Comm_rank (comm, &rank);
>    ......
> }
> 
> For all MPI functions I need the right communicator (MPI_Comm *comm;) to 
> communicate with the existing slaves. This variable will be generated by 
> spawning the Rslaves (mpi.spawn.Rslaves). But how to get to this 
> variable in my C function?
> Is the communicator variable somewhere stored in a R variable?
> 
> ( I use R 2.6.2 and Rmpi 0.5-5)
> 
> Thanks
> Markus
> 


-- 
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109

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