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KNOWN_PROBLEMS.md

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Known problems

  • If the CUDA support is enabled, then the starneig_SEP_SM_Hessenberg() interface function cannot always handle problems that do not fit into GPU's memory. The cause of this problem is not known.
  • The outputs of the starneig_GEP_SM_Schur() and starneig_GEP_DM_Schur() interface functions are not always in the so-called standard format. It is possible that some diagonal entries in the right-hand side output matrix are negative.
  • The starneig_GEP_SM_Eigenvectors() interface function may scale the input matrices.

Known compatibility problems

BLAS

  • With some OpenBLAS versions, it is necessary to set the OPENBLAS_NUM_THREADS environmental variable to value 1 (export OPENBLAS_NUM_THREADS=1).
  • Some MKL versions can cause poor scalability. The problem appears to be related to Intel's OpenMP library. Setting the KMP_AFFINITY environmental variable to value disabled fixes the problem (export KMP_AFFINITY=disabled).
  • OpenBLAS version 0.3.1 has a bug that can cause an incorrect result.
  • OpenBLAS versions 0.3.3-0.3.5 can cause poor scalability.

MPI

  • Some older OpenMPI versions (<= 2.1.1) have a bug that can cause a segmentation fault during a parallel AED.
  • The library has an unsolved memory leak problem with OpenMPI. Only large problem sizes are effected. It is not known whether this problem is related to StarNEig, StarPU, OpenMPI or something else. The problem is known to occur with PMIx 2.2.1, UCX 1.5.0, OpenMPI 3.1.3, and StarPU 1.2.8. The memory leak is sometimes accompanied by the following warning:
mpool.c:38   UCX  WARN  object 0x2652000 was not returned to mpool ucp_requests

StarPU

  • For optimal CUDA performance, StarPU version that is newer than 1.3.3 is recommended.
  • StarPU versions 1.2.4 - 1.2.8 and some StarPU 1.3 snapshots cav cause poor CUDA performance. The problem can be fixed by compiling StarPU with --disable-cuda-memcpy-peer. It is possible that newer versions of StarPU are also effected by this problem.
  • The STARPU_MINIMUM_AVAILABLE_MEM and STARPU_TARGET_AVAILABLE_MEM environmental variables can be used to fix some GPU-related memory allocation problems:
STARPU_MINIMUM_AVAILABLE_MEM=10 STARPU_TARGET_AVAILABLE_MEM=15 ...