I think Lisandro's point is that KSPSolve does not set ksp->its = 0.
That happens in each KSPSolve_XXX. The Python implementation of a KSP
forgot to do that, but perhaps it should happen in KSPSolve.
"Smith, Barry F. via petsc-dev" <petsc-dev@mcs.anl.gov> writes:
> I'm a bit confused. Since the C KSPSolve() always resets the counter to
> zero I don't understand why the Python call (which presumably calls the C
> version doesn't get it reset). Or does the python version not call the C
> version.
>
> I'm fine with either solution I guess but I'd like to understand why the C
> behavior doesn't just automatically happen with the Python.
>
> Barry
>
>
>> On Mar 4, 2019, at 12:07 AM, Lisandro Dalcin <dalc...@gmail.com> wrote:
>>
>> I pushed the fix to branch dalcinl/fix-ksp-ex100
>>
>> On Mon, 4 Mar 2019 at 09:01, Lisandro Dalcin <dalc...@gmail.com> wrote:
>> Well, this is just because the Python code implementing KSPSolve does not
>> reset the iteration counter to zero. This was an oversight on my part when I
>> wrote that code ages ago.
>>
>> Barry, I'm wondering whether this should be done at the interface rather
>> than implementation level? If you do not want to change things in core KSP
>> (and then maybe SNES, etc), the the following patch should fix things.
>>
>>
>> diff --git a/src/ksp/ksp/examples/tutorials/example100.py
>> b/src/ksp/ksp/examples/tutorials/example100.py
>> index ef085522bf..7ad03ec194 100644
>> --- a/src/ksp/ksp/examples/tutorials/example100.py
>> +++ b/src/ksp/ksp/examples/tutorials/example100.py
>> @@ -119,11 +119,13 @@ class ConjGrad(object):
>>
>> def solve(self, ksp, b, x):
>> LOG('ConjGrad.solve()')
>> + ksp.setIterationNumber(0)
>> A, P = get_op_pc(ksp, transpose=False)
>> pcg(ksp, A, P, b, x, *self.work)
>>
>> def solveTranspose(self, ksp, b, x):
>> LOG('ConjGrad.solveTranspose()')
>> + ksp.setIterationNumber(0)
>> A, P = get_op_pc(ksp, transpose=True)
>> pcg(ksp, A, P, b, x, *self.work)
>>
>>
>> On Mon, 4 Mar 2019 at 06:15, Smith, Barry F. <bsm...@mcs.anl.gov> wrote:
>>
>> Pierre,
>>
>> I can confirm the problem.
>>
>> Lisandro,
>>
>> Could you please take a look at this? I have no explanation for why
>> this would happen.
>>
>> Barry
>>
>>
>>
>> > On Feb 25, 2019, at 1:21 PM, Pierre Jolivet via petsc-dev
>> > <petsc-dev@mcs.anl.gov> wrote:
>> >
>> > I’m not sure this is the expected behavior. Is it?
>> > $ git diff ex100.py
>> > diff --git a/src/ksp/ksp/examples/tutorials/ex100.py
>> > b/src/ksp/ksp/examples/tutorials/ex100.py
>> > index dbb3f8e012..051637ce1d 100644
>> > --- a/src/ksp/ksp/examples/tutorials/ex100.py
>> > +++ b/src/ksp/ksp/examples/tutorials/ex100.py
>> > @@ -29,6 +29,7 @@ def RunTest():
>> > ksp.setOperators(A, A)
>> > ksp.setFromOptions()
>> > ksp.solve(b, x)
>> > + ksp.solve(b, x)
>> >
>> > r = b.duplicate()
>> > A.mult(x, r)
>> >
>> > $ mpirun -np 8 python ./ex100.py -ksp_converged_reason -ksp_monitor
>> > 0 KSP Residual norm 5.101520253035e-04
>> > 1 KSP Residual norm 1.168905135944e-03
>> > [..]
>> > 12 KSP Residual norm 5.101520253035e-05
>> > 13 KSP Residual norm 7.504522604366e-20
>> > Linear solve converged due to CONVERGED_RTOL iterations 13
>> > 13 KSP Residual norm 5.101520253035e-04
>> > 14 KSP Residual norm 1.168905135944e-03
>> > [..]
>> > 25 KSP Residual norm 5.101520253035e-05
>> > 26 KSP Residual norm 7.504522604366e-20
>> > Linear solve converged due to CONVERGED_RTOL iterations 26
>> >
>> > Shouldn’t the iterate number be reset to 0 for the 2nd KSPSolve?
>> >
>> > Thanks,
>> > Pierre
>>
>>
>>
>> --
>> Lisandro Dalcin
>> ============
>> Research Scientist
>> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
>> Extreme Computing Research Center (ECRC)
>> King Abdullah University of Science and Technology (KAUST)
>> http://ecrc.kaust.edu.sa/
>>
>> 4700 King Abdullah University of Science and Technology
>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
>> Thuwal 23955-6900, Kingdom of Saudi Arabia
>> http://www.kaust.edu.sa
>>
>> Office Phone: +966 12 808-0459
>>
>>
>> --
>> Lisandro Dalcin
>> ============
>> Research Scientist
>> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
>> Extreme Computing Research Center (ECRC)
>> King Abdullah University of Science and Technology (KAUST)
>> http://ecrc.kaust.edu.sa/
>>
>> 4700 King Abdullah University of Science and Technology
>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
>> Thuwal 23955-6900, Kingdom of Saudi Arabia
>> http://www.kaust.edu.sa
>>
>> Office Phone: +966 12 808-0459
