[petsc-users] PCASM in transposed format

[Antoine De Blois]

Dear all,

I am using the ASM preconditioner to solve a transposed system through MatSolveTranspose. Strangely, the results I obtain differ in each call. Is there a non-deterministic operations within ASM? If I use it in a non-transposed way, I get correct results... If I use GASM, then the results are always the same, both in transposed and non-transposed formats.

Below is a log of my calls (note that some of them actually diverged).
I can give you my matrix and rhs if you want.

Regards,
Antoine

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 690
Residual norm 0.000617544

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 475
Residual norm 0.000727253

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 10000
Residual norm 1.3866

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 568
Residual norm 0.000684401

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 540
Residual norm 0.000555548

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 10000
Residual norm 1.30198

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type asm
Number of iterations = 207
Residual norm 0.000555849


---------------

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type gasm
Number of iterations = 297
Residual norm 0.000600143

$ mpirun -np 4 /gpfs/fs1/aero/SOFTWARE/TOOLS/PROGRAMMING/petsc/src/ksp/ksp/examples/tutorials/ex10 -f0 A_and_rhs.bin  -trans -pc_type gasm
Number of iterations = 297
Residual norm 0.000600143



Antoine DeBlois
Specialiste ingenierie, MDO lead / Engineering Specialist, MDO lead
Aéronautique / Aerospace
514-855-5001, x 50862
antoine.deblois at aero.bombardier.com<mailto:antoine.deblois at aero.bombardier.com>

2351 Blvd Alfred-Nobel
Montreal, Qc
H4S 1A9

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