.. include:: system.rst .. _jureca_faq: FAQ === Here you can find a list of frequently askes questions about |SYSTEM_NAME|: FAQ about |SYSTEM_NAME| +++++++++++++++++++++++ How can Intel MPI be tuned for the JURECA InfiniBand network? ------------------------------------------------------------- By default, Intel MPI uses uDAPL (Direct Access Programming Library) for inter-node MPI communication via the InfiniBand fabric. In many cases better performance can be achieved with the low-level OFED ``libibverbs`` library. In order to select the ``ofa`` fabric for Intel MPI inter-node communication, export the following environment variable in your job script or ``salloc`` session: .. code-block:: export I_MPI_FABRIC=shm:ofa How can a compute node in an active allocation be accessed? ----------------------------------------------------------- In order to obtain a shell on a compute node on which a job is currently running the following command can be used. .. code-block:: srun -n 1 -N 1 --jobid -r --cpu_bind=none --gres=gpu:0 --pty /bin/bash -i Here, ```` must be replaced with the id of the allocated job and ```` specifies the relative node number (starting at zero) within the nodes allocated to the job. Error Messages on |SYSTEM_NAME| +++++++++++++++++++++++++++++++ What does the error message "vsetenv ... failed" mean? ------------------------------------------------------ The warning message .. code-block:: Note: Max supported value for env var is 4095 vsetenv ... failed is generated by the InfiniBand driver userspace library when an environment variable exceeds the limit of 4095 characters. This warning has no effect on the running job and can safely be ignored until a fix is available. .. include:: ../shared/faq.rst FAQ about Data Management +++++++++++++++++++++++++ .. include:: ../shared/faq-just.rst