[mpich-discuss] SMP and mpd.hosts

[Torquil Macdonald Sørensen]

Torquil Macdonald Sørensen wrote:
> Hi all,
> 
> I would like to ask for some help concerning the use of MPICH2 1.1 on a 
> dual-core machine with Linux. My mpich2 innstallation uses the nemesis 
> communication device, which I thought was able to utilise both cores, in 
> addition to communicate through the network.
> 
>  From before (maybe from mpich1?) I had a mpd.hosts file with the 
> following syntax:
> 
> dagda.uio.no:2
> #styx.uio.no:2
> 
> where the :2 was to indicate the number of CPUS. styx.uio.no is 
> commented out because this time I want two processes to run on 
> dagda.uio.no. But I am no longer sure of this syntax since I cannot find 
> it in the documentation. I was hoping that the following would work:
> 
> $ mpdboot -n 2
> $ mpiexec -n 2 ./Executable
> 
> However, mpdboot complains:
> 
> "totalnum=2  numhosts=1
> there are not enough hosts on which to start all processes"
> 
> What it the common method to run a program so that it will be able to 
> distribute itself across several cpu-cores in one machine, and also 
> across the network, if I e.g. decomment styx.uio.no and use -n 4 in the 
> above commands?
> 
> Best regards
> Torquil Sørensen
> 

It seems to be possible to get two processes by using "mpdboot -1 -n 2". 
   I guess that means that it starts more than one mpd. In that case 
"mpiexec -n prog" works. So I guess I was suffering a limitation of max 
one process per mpd?

-Torquil