Ada: Code execution in interactive mode

Execution of a sequential code in interactive mode

The execution of a sequential program on Ada in interactive mode is limited by the following:

  • Process CPU time: 30 minutes
  • Total memory for the job < 3.5 GB

If the program needs more resources than this, it is necessary to submit it in batch mode.

To know the limits of the interactive mode in detail:

$ ulimit -Ha

Execution of an MPI parallel code in interactive mode

The execution of a parallel MPI program on Ada in interactive mode is limited by the following:

  • Elapsed time (clock time): 30 minutes
  • Memory for each MPI task < 3.5 GB
  • Number of tasks < 32

If the program needs more resources than this, it is necessary to submit it in batch mode.

The following is an example of an interactive execution for a parallel program on 4 processors (for example, with an executable file named poisson_MPI):

$ export MP_PROCS=4
$ poe ./poisson_MPI

or directly :

$ poe ./poisson_MPI -procs 4

The interactive parallel executions are in competition with the parallel jobs. When the resources requested are not available, you receive the following message:

ERROR: 0031-365  LoadLeveler unable to run job, reason:
LoadL_negotiator: 2544-870 Step ada338.idris.fr.1613.0 was not considered
to be run in this scheduling cycle due to its relatively
low priority or because there are not enough free resources.

Execution in interactive mode of a multi-thread parallel code with shared memory

The interactive execution of a parallel program with shared memory (parallelized with OpenMP, or automatically) on Ada is limited by the following:

  • Process CPU time: 30mn
  • Total memory for the job < 3.5 GB
  • Maximum number of threads: 4

If the program needs more resources than this, it is necessary to submit it in batch mode.

The following is an example of an interactive execution for an OpenMP program requiring 4 threads (OpenMP threads) :

$ export OMP_NUM_THREADS=4
$ ./prog

If your program was parallelized automatically, you can use the same commands with the same variable OMP_NUM_THREADS, to control the number of light processes.

Execution of a hybrid MPI/OpenMP parallel code in interactive mode

The interactive execution of a hybrid parallel (MPI + threads) program on Ada is limited by the following :

  • Elapsed time (restitution time): 30 minutes
  • Memory per MPI task limited < 3.5 GB
  • Maximum of 32 MPI tasks and 4 OpenMP threads per MPI process.

If the program needs more resources than this, it is necessary to submit it in batch mode.

The following is an example of an interactive execution of a hybrid parallel program with 4 MPI tasks and 2 OpenMP threads for each MPI task:

$ export OMP_NUM_THREADS=2
$ export MP_PROCS=4
$ poe ./poisson_MPI_OMP