Known Issues

The following selection describes known bugs, errors, or other difficulties that may occur when using libEnsemble.

  • When using the Executor: OpenMPI does not work with direct MPI task submissions in mpi4py comms mode, since OpenMPI does not support nested MPI executions. Use either local mode or the Balsam Executor instead.

  • Local comms mode (multiprocessing) may fail if MPI is initialized before forking processors. This is thought to be responsible for issues combining multiprocessing with PETSc on some platforms.

  • Remote detection of logical cores via LSB_HOSTS (e.g., Summit) returns the number of physical cores as SMT info not available.

  • TCP mode does not support (1) more than one libEnsemble call in a given script or (2) the auto-resources option to the Executor.

  • libEnsemble may hang on systems with matching probes not enabled on the native fabric, like on Intel’s Truescale (TMI) fabric for instance. See the FAQ for more information.

  • We currently recommended running in Central mode on Bridges as distributed runs are experiencing hangs.