On 2020-05-23 23:45, Satish Balay wrote:
One more issue: Most externalpackages don't support 64bit-indices.
Note: OpenBLAS supports 64bit indices. MKL has bunch of packages built
as ILP64
[MPICH/OpenMPI - as far as I know is LP64]
The primary reason PETSc defaults to 32bit indices is - this is the
compiler default on LP64 systems.
If debian is building ILP64 system [with compilers defaulting to
64-bit integers] - that would mean all packages would be ILP64
[obviously most packages are not tested in this mode - so might break]
--with-64-bit-indices is the option for 64-bit-indices on LP64 systems
which most packages don't support - hence the usage of PetscBLASInt
PetscMPIInt etc.
If I remember correctly - the 'full 64-bit' mode relies on fortran
compiler
option '-i8' - which is basally equivalent to ILP64 - and this mode
only works
with ILP64 MPI, BLAS etc from Intel-MPI/MKL
If I understand correctly, the Debian systems are LP64 (so gcc defaults
to int=int32_t).
Our user who started these discussions with Bug#953116 reports that
--with-64-bit-indices is working fine for his local build. But he may
not have tested using MUMPS in 64-bit PETSc.
We haven't tried using MUMPS in this mode with PETSc
This will be the interesting test. I'll start with the 64-bit build of
MUMPS and see how tests hold up.
Drew
