Re: [Rd] Rmpi_0.5-4 and OpenMPI questions

From: Dirk Eddelbuettel <edd_at_debian.org>
Date: Thu, 4 Oct 2007 05:31:55 -0500

On 4 October 2007 at 01:11, Hao Yu wrote:
| Hi Dirk,
|
| Thank for pointing out additional flags needed in order to compile Rmpi
| correctly. Those flags can be added in configure.ac once openmpi dir is
| detected. BTW -DMPI2 flag was missed in your Rmpi since the detection of
| openmpi was not good. It should be
| ####
| if test -d ${MPI_ROOT}/lib/openmpi; then
| echo "Found openmpi dir in ${MPI_ROOT}/lib"
| MPI_DEPS="-DMPI2"
| fi
| ####

I don't follow. From my build log:

so -DMPI2 is used.

Because I build this in a chroot / pbuilder envinronment, neither LAM nor MPICH2 are installed and Open MPI is detected.

| I tried to run Rmpi under snow and got the same error messenger. But after
| checking makeMPIcluster, I found that n=3 was a wrong argument. After
| makeMPIcluster finds that count is missing,

Yes, my bad. But it also hangs with argument count=3 (which I had tried, but my mail was wrong.)

| count=mpi.comm.size(0)-1 is used. If you start R alone, this will return
| count=0 since there is only one member (master). I do not know why snow
| did not use count=mpi.universe.size()-1 to find total nodes available.

How would it know total nodes ? See below re hostfile.

| Anyway after using
| cl=makeMPIcluster(count=3),
| I was able to run parApply function.
|
| I tried
| R -> library(Rmpi) -> library(snow) -> c1=makeMPIcluster(3)
|
| Also
| mpirun -host hostfile -np 1 R --no-save
| library(Rmpi) -> library(snow) -> c1=makeMPIcluster(3)
|
| Hao
|
| PS: hostfile contains all nodes info so in R mpi.universe.size() returns
| right number and will spawn to remote nodes.

So we depend on a correct hostfile ? As I understand the Open MPI this is deprecated:

# This is the default hostfile for Open MPI.  Notice that it does not
# contain any hosts (not even localhost).  This file should only
# contain hosts if a system administrator wants users to always have
# the same set of default hosts, and is not using a batch scheduler
# (such as SLURM, PBS, etc.).

I am _very_ interested in running Open MPI and Rmpi under slurm (which we added to Debian as source package slurm-llnl) so it would be nice if this could rewritten to not require a hostfile as this seems to be how upstream is going.

| Rmp under Debian 3.1 and openmpi 1.2.4 seems OK. I did find some missing
| lib under Debian 4.0.

Can you be more specifi? I'd be glad to help.

Thanks!

Dirk

|
|
| Dirk Eddelbuettel wrote:
| >
| > Many thanks to Dr Yu for updating Rmpi for R 2.6.0, and for starting to
| > make
| > the changes to support Open MPI.
| >
| > I have just built the updated Debian package of Rmpi (i.e. r-cran-rmpi)
| > under
| > R 2.6.0 but I cannot convince myself yet whether it works or not. Simple
| > tests work. E.g. on my Debian testing box, with Rmpi installed directly
| > using Open Mpi 1.2.3-2 (from Debian) and using 'r' from littler:
| >
| > edd_at_ron:~> orterun -np 3 r -e 'library(Rmpi); print(mpi.comm.rank(0))'
| > [1] 0
| > [1] 1
| > [1] 2
| > edd_at_ron:~>
| >
| > but I basically cannot get anything more complicated to work yet. R /
| > Rmpi
| > just seem to hang, in particular snow and and getMPIcluster() just sit
| > there:
| >
| >> cl <- makeSOCKcluster(c("localhost", "localhost"))
| >> stopCluster(cl)
| >> library(Rmpi)
| >> cl <- makeMPIcluster(n=3)
| > Error in makeMPIcluster(n = 3) : no nodes available.
| >>
| >
| > I may be overlooking something simple here, in particular the launching of
| > apps appears to be different for Open MPI than it was with LAM/MPI (or
| > maybe
| > I am just confused because I also look at LLNL's slurm for use with Open
| > MPI ?)
| >
| > Has anybody gotten Open MPI and Rmpi to work on simple demos? Similarly,
| > is
| > anybody using snow with Rmpi and Open MPI yet?
| >
| > Also, the Open MPI FAQ is pretty clear on their preference for using mpicc
| > for compiling/linking to keep control of the compiler and linker options
| > and
| > switches. Note that e.g. on my Debian system
| >
| > edd_at_ron:~> mpicc --showme:link
| > -pthread -lmpi -lopen-rte -lopen-pal -ldl -Wl,--export-dynamic -lnsl
| > -lutil -lm -ldl
| >
| > whereas Rmpi built with just the default from R CMD:
| >
| > gcc-4.2 -std=gnu99 -shared -o Rmpi.so RegQuery.o Rmpi.o conversion.o
| > internal.o -L/usr/lib -lmpi -lpthread -fPIC -L/usr/lib/R/lib -lR
| >
| > Don't we need libopen-rte and libopen-pal as the MPI FAQ suggests?
| >
| > Many thanks, Dirk
| >
| > --
| > Three out of two people have difficulties with fractions.
| >
|
|
| --
| Department of Statistics & Actuarial Sciences
| Fax Phone#:(519)-661-3813
| The University of Western Ontario
| Office Phone#:(519)-661-3622
| London, Ontario N6A 5B7
| http://www.stats.uwo.ca/faculty/yu

-- 
Three out of two people have difficulties with fractions.

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