[R-pkgs] doMPI 0.1-4

[Stephen Weston]

I'd like to announce the availability of version 0.1-4 of the "doMPI"
package, a parallel backend for the "foreach" package, which acts as an
adaptor to the "Rmpi" package.  The package has been uploaded to CRAN
and is now available under the GPL-2 license.

In addition to fixing a few problems in version 0.1-3, the main new
feature of this release is the backend-specific "initEnvirMaster"
option, which specifies an R function that is executed in the master
process at the beginning of the foreach loop.  It is intended to be used
in conjunction with the "initEnvir" option, which specifies an R
function that is executed by the cluster workers.  By using both
together, MPI collective communication functions can be executed to
initialize the cluster workers.  This is particularly useful for sending
large matrices to each of the workers, since it allows the matrix to be
broadcast using the mpi.bcast function without calling the R "serialize"
function.  An example of this technique is in the new "rforest.R" file,
a parallel random forest benchmark which is included in the "benchmark"
directory of the doMPI distribution.

- Steve Weston