Re: [slurm-users] ntasks and cpus-per-task

On 23/02/18 21:50, Loris Bennett wrote: OK, I'm confused now. Our main culprit for producing processes with incorrect affinity is ORCA [1]. It uses OpenMPI but also likes to start processes asynchronously via SSH within the node set. In that case (and for the general case where there are

Re: [slurm-users] ntasks and cpus-per-task

Hi Chris, Christopher Benjamin Coffey writes: > Hi Loris, > >> But that's only the case if the program is started with srun or some >> form of mpirun. Otherwise the program just gets started once on one >> core and the other cores just idle. > > Yes, maybe that’s true

Re: [slurm-users] ntasks and cpus-per-task

On 02/22/2018 07:50 AM, Christopher Benjamin Coffey wrote: It’s a big deal if folks use -n when it’s not an mpi program. This is because the non mpi program is launched n times (instead of once with internal threads) and will stomp over logs and output files (uncoordinated) leading to poor

Re: [slurm-users] ntasks and cpus-per-task

Hi Loris, "But that's only the case if the program is started with srun or some form of mpirun. Otherwise the program just gets started once on one core and the other cores just idle." Yes, maybe that’s true about what you say when not using srun. I'm not sure, as we tell everyone to

Re: [slurm-users] ntasks and cpus-per-task

Yeah, I've found that in those situations to have people wrap their threaded programs in srun inside of sbatch.  That way the scheduler knows which process specifically gets the threading. -Paul Edmon- On 02/22/2018 10:39 AM, Loris Bennett wrote: Hi Paul, Paul Edmon

Re: [slurm-users] ntasks and cpus-per-task

Hi Paul, Paul Edmon writes: > At least from my experience wonky things can happen with slurm > (especially if you have thread affinity on) if you don't rightly > divide between -n and -c.  In general I've been telling our users that > -c is for threaded applications and

Re: [slurm-users] ntasks and cpus-per-task

Loris, It’s simple, tell folks only to use -n for mpi jobs, and -c otherwise (default). It’s a big deal if folks use -n when it’s not an mpi program. This is because the non mpi program is launched n times (instead of once with internal threads) and will stomp over logs and output files

Re: [slurm-users] ntasks and cpus-per-task

Hi, That was just I thought, ntasks for mpi and cpus-per-task for multithreading. So, for example, if every node has 24 cores, is there any difference between these commands? sbatch --ntasks 24 [...] sbatch --ntasks 1 --cpus-per-task 24 [...] regards. El jue., 22 feb. 2018 a las 9:52, Loris

Re: [slurm-users] ntasks and cpus-per-task

On 22/02/18 18:49, Miguel Gutiérrez Páez wrote: What's the real meaning of ntasks? Has cpus-per-task and ntasks the same meaning in sbatch and srun? --ntasks is for parallel distributed jobs, where you can run lots of independent processes that collaborate using some form of communication