[petsc-users] sparse direct solver and number of nonzero elements

[Xiangdong Liang]

Hello everyone,

I am solving Ax=b with sparse direct solver Pastix. I have two
equivalent A's (upto these zero entries): A1 and A2. A1 is generated
with ignor_zero_entries and A2 is without this option. For example A1
has 9 millions nonzeros, while A2 has 10 millions zeros. When I solve
them with Pastix, I found the time for solving sparser A1 actually is
longer (10%--20% worse) than A2. Does anyone have thoughts on this?
Thanks.

Xiangdong

P.S. The time I count is only for Spare LU solving (not including the
matrix assembling time).