[R] Status of Rmpi--Good with tweaks

[Na Li]

On 24 Mar 2004, Ross Boylan outgrape:

> By the way, I'm in the dark about (r)sprng.  From some of the snow docs,
> I thought that was really snow's business.  But your site notes that the
> Rmpi packages are withough SPRNG support.  And Tony Rossini's pages (I
> think) had a slightly cryptic remark that SPRNG under MPI was a bit
> dicey.

rsprng works like this: each process calls the function init.sprng, with
three pieces of information: 1) the total number of processes; 2) the rank
of current process; 3) a seed that is the same for all processes.

An alternative is that the master generates say ten streams, and send one
stream to each slave (and keep track of who gets what, to ensure
reproducibility).

Only very little (and simple) inter-process communication is required for
SPRNG. The communication layer is orthogonal of SPRNG itself.  rsprng can
be used with Rmpi just fine.  (SPRNG can be used in serial code as well.)

If you look at SPRNG source, it has some sort of MPI support, which is
disabled when I compile SPRNG.  See this note:

http://www.biostat.umn.edu/~nali/RsprngNotes.php

Cheers,

Michael