On Wed, May 17, 2023 at 9:02 AM Fleischli Benno HSLU T&A <benno.fleischli@hslu.ch> wrote:
Dear PETSc developers

I am creating a very large parallel sparse matrix (MATMPIAIJ) with PETSc. I write this matrix to disk.
The number of non-zeros exceeds the maximum number a 32-bit integer can hold.
When I read the matrix from disk i get an error because there was an overflow in the nz number.
(see petsc-3.18.4/src/mat/impls/aij/seq/aij.c:4977)

Obviously I could compile PETSc with 64bit integers (--with-64-bit-indices).
But I wanted to ask if there is another way. Because the total number of nonzeros nz is the only numer that exceeds the 32bit limit.
It would not be efficient to use 64bit integers everywhere just because of this single number.

Integers tend to be a small part of the overall storage. How much does it increase the maximum overall storage for your problem?

  Thanks,

     Matt
 
This how I configured PETSc:

./configure --download-fblaslapack --download-hpddm --download-hypre --with-debugging=0
COPTFLAGS='-O3 -march=native -mtune=native' CXXOPTFLAGS='-O3 -march=native -mtune=native'
FOPTFLAGS='-O3 -march=native -mtune=native' --with-scalar-type=real (--with-mpi-dir=/home/benno/Libraries/openMPI)



Kind Regards

Benno



________________________________

Hochschule Luzern
Technik & Architektur
Institute for Mechanical Engineering and Energy Technology

Competence Center Fluid Mechanics and Numerical Methods


Benno Fleischli
MSc in Mechanical Engineering / BSc in Electrical Engineering

Wissenschaftlicher Mitarbeiter

benno.fleischli@hslu.ch




--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener