Hello,
I've attached a simplified version of my code that reproduces the problem
I'm having, namely that the adjoint calculated has a very nonzero residual
when the residual is calculated manually from the transpose of
system.matrix and adjoint_rhs. The simplified system has two variables;
I've not yet been able to replicate the phenomenon with a single-variable
system, though I am not sure whether that is a coincidence or related to
the problem.
Thanks,
Harriet
On Sun, Jan 4, 2015 at 2:54 PM, Kameeko Kiwi <[email protected]> wrote:
> Hello,
>
> In case there were initialization issues arising from my not having
> performed a forward solve first, I added print lines after line 824 in
> petsc_linear_solver.C, after the matrices and vectors are closed, to see if
> PetscLinearSolver::adjoint_solve was trying to solve the correct linear
> system. The matrix_in and rhs_in are what I expect them to be and match the
> ones used to manually calculate the residual that turned out to be grossly
> nonzero.
>
> Thanks,
> Harriet
>
> On Tue, Dec 30, 2014 at 9:47 PM, Kameeko Kiwi <[email protected]> wrote:
>
>> Hello,
>>
>> I'm trying to solve an adjoint problem for a linear system without first
>> solving the forward system. libMesh is giving me an adjoint solution which
>> results in a grossly non-zero residual (calculated using system.matrix and
>> system.get_adjoint_rhs, since the Jacobian is symmetric for now) , O(e-4)
>> in L2. However, the final residual output given by adjoint_solve() is
>> O(e-11). This occurred on two separate computers, so I don't believe it is
>> a product of my particular petsc installation.
>>
>> If I use the debugging options to print out the jacobian and adjoint rhs,
>> copy them into Matlab and calculate the adjoint solution there, I get a
>> solution for which the manually calculated residual (calculated in libMesh
>> by reading in the Matlab solution from a text file) is much smaller
>> (O(e-15)).
>>
>> If I implement the adjoint system as the forward problem and solve it
>> using system.solve(), I get a solution that agrees with that produced by
>> Matlab.
>>
>> It seems that the adjoint is not being solved to the user specified
>> accuracy. Shrinking solver->initial_linear_tolerance (currently at e-10)
>> did not help. I can send my code if needed.
>>
>> Thanks,
>> Harriet
>>
>
>
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