buket at be.itu.edu.tr buket at be.itu.edu.tr
Sun Feb 19 11:34:34 CST 2006

I am trying to solve a linear system of vibroacoustic Problem with 12328

When I use bcgs and ilu(1) with n=1 proc, I get:

---Norm of residual=4.58868e+17
---Norm of error(u-x)=75.0051
---Number of iteration=7
---Solution Time=3.896039 second

When I use bcgs and ilu(2) with n=1 proc, I get a different error message:

---[0]PETSC ERROR: MatLUFactorNumeric_SeqAIJ() line 537 in
   [0]PETSC ERROR:   Detected zero pivot in LU factorization!
   [0]PETSC ERROR:   Zero pivot row 10816 value 5.0874e+06 tolerance 1e-12
* rs 7.29416e+20!
   [0]PETSC ERROR: MatLUFactorNumeric() line 1831 in

That system seems to converge immediately, at first, with 7 iters. But the
norm of residual is increadibly high. Did you face with that situation?
Can that be the result of divergence?

Best Regards,
Buket Benek

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