[petsc-users] Question on MatCreateSeqAIJ() and 32-bit integer

[Lu Qiyue]

Dear All:

I am solving a huge system AX=b, A is a sparse matrix but its number of
non-zeros is 3.29*10^9. I noticed that the 32-bit integer upper limit is
~2.15*10^9.

A is in COO format here. When I prepare the input *.bin file for Petsc, the
line

ierr = MatCreateSeqAIJ(PETSC_COMM_WORLD,m,n,0,cnt,&A);CHKERRQ(ierr);

can not pass.

m =n =39979380 here, cnt is an array holding the number of non-zeros per
row. The error message is:

[0]PETSC ERROR: Out of memory. This could be due to allocating
[0]PETSC ERROR: too large an object or bleeding by not properly
[0]PETSC ERROR: destroying unneeded objects.
[0]PETSC ERROR: Memory allocated 0 Memory used by process 492802048
[0]PETSC ERROR: Try running with -malloc_dump or -malloc_log for info.
[0]PETSC ERROR: Memory requested 18446744061813993472!

Calling MatCreateSeqAIJ() doesn't involve NNZ information there, m/n/cnt
are all integers less than 32-bit integer limit.
And the total size of data in COO format: nnz*8 bytes(values)+nnz*4
bytes(rows)+nnz*4 bytes(cols) are less than the memory limit of our system.

The code works on a system with half size of this failed one.

I am wondering, Does this because MatCreateSeqAIJ() might do some
'internal' counting things which exceeds the integer limit in this case?

Thanks

Qiyue Lu
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