Matrix convergence.

[Barry Smith]

   You did not type it right -sub_pc_type lu not -pc_type lu


On Fri, 3 Mar 2006, billy at dem.uminho.pt wrote:

>
> This is what I get:
>
> [0]PETSC ERROR: MatLUFactorSymbolic() line 2159 in src/mat/interface/matrix.c
> [0]PETSC ERROR: No support for this operation for this object type!
> [0]PETSC ERROR: Matrix type mpiaij  symbolic LU!
> [0]PETSC ERROR: PCSetUp_LU() line 252 in src/ksp/pc/impls/factor/lu/lu.c
> [0]PETSC ERROR: PCSetUp() line 798 in src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: KSPSetUp() line 234 in src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: KSPSolve() line 334 in src/ksp/ksp/interface/itfunc.c
>
>
> Quoting Barry Smith <bsmith at mcs.anl.gov>:
>
>>
>>    Run the parallel PETSc job with -ksp_type gmres -ksp_gmres_restart 200
>> -sub_pc_type lu
>>
>>
>> On Fri, 3 Mar 2006, billy at dem.uminho.pt wrote:
>>
>>> Hi,
>>>
>>> I tried to solve the 18x18 matrix with laspack and the results are the
>> following:
>>>
>>> Solver: GMRES, Preconditioning: NULL, Iterations: 500, Residual: 6.16E-2
>>> Solver: GMRES, Preconditioning: SSOR, Iterations: 500, Residual: 6.57E-2
>>> Solver: GMRES, Preconditioning: ILU, ERROR
>>>
>>> Solver: BiCGSTAB, Preconditioning: NULL, Iterations: 101, Residual:
>> 8.88E-7
>>> Solver: BiCGSTAB, Preconditioning: SSOR, Iterations: 36, Residual:
>> 9.87E-7
>>> Solver: BiCGSTAB, Preconditioning: ILU, ERROR
>>>
>>>
>>> Billy.
>>>
>>>
>>> Quoting Barry Smith <bsmith at mcs.anl.gov>:
>>>
>>>>
>>>>    Billy,
>>>>
>>>>     Most likely there is something wrong with the matrix being
>>>> generated. I would first look at the matrix entries and make
>>>> sure they make sense. Then I would solve the linear systems
>>>> with a direct solver -pc_type lu (on one processor and make
>>>> sure the solutions are reasonable and your simulation has
>>>> "correct" answers).
>>>>
>>>>    It is possible the parallel matrix generation is wrong,
>>>>
>>>>    Barry
>>>>
>>>>
>>>> On Thu, 2 Mar 2006, billy at dem.uminho.pt wrote:
>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>>
>>>>> I have been testing my parallel implementation with a 2D case. I have
>> used
>>>> the
>>>>> following grids with 2 and 4 processes: 4x4, 10x10, 16x16 and 18x18.
>>>>>
>>>>> It works for the first three (max. number of iterations to converge
>> aprox.
>>>> 70)
>>>>> but when I increase to 18x18 the matrix does not converge. I have
>> increased
>>>> the
>>>>> maximum number of iterations and I have used GMRES, BiCGSTAB with
>>>>> preconditioners ASM, JACOBI, etc.
>>>>>
>>>>> With KSPType = GMRES and PCType = ASM:
>>>>> Number of iterations: 500 Residual: +1.420471E-01
>>>>>
>>>>> With KSPType = GMRES and PCType = JACOBI:
>>>>> Number of iterations: 500 Residual: +2.351882E-02
>>>>>
>>>>> With KSPType = BCGS and PCType = ASM:
>>>>> Number of iterations: 136 Residual: +3.911446E+04
>>>>>
>>>>> With KSPType = BCGS and PCType = NULL:
>>>>> Number of iterations: 157 Residual: +3.254728E+03
>>>>>
>>>>> Is it normal that the convergence detiorates so much with such a slight
>>>> increase
>>>>> in the dimension of the matrix? Is there any optimization parameter that
>> I
>>>> may
>>>>> be missing?
>>>>>
>>>>>
>>>>> Billy.
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>
>
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