https://bitbucket.org/petsc/petsc/issues/333/use-64-bit-indices-for-row-offsets-in
"Smith, Barry F." <[email protected]> writes: > Make an issue > > >> On Jul 30, 2019, at 7:00 PM, Jed Brown <[email protected]> wrote: >> >> "Smith, Barry F. via petsc-users" <[email protected]> writes: >> >>> The reason this worked for 4 processes is that the largest count in that >>> case was roughly 6,653,750,976/4 which does fit into an int. PETSc only >>> needs to know the number of nonzeros on each process, it doesn't need to >>> know the amount across all the processors. In other words you may want to >>> use a different PETSC_ARCH (different configuration) for small number of >>> processors and large number depending on how large your problem is. Or you >>> can always use 64 bit integers at a little performance and memory cost. >> >> We could consider always using 64-bit ints for quantities like row >> starts, keeping column indices (the "heavy" part) in 32-bit. This may >> become a more frequent issue with fatter nodes and many GPUs potentially >> being driven by a single MPI rank.
