Trying again.
Normally, numIts would be one less than nEntries since the initial residual
is computed (and stored in the history) before any iterations.
Is this what you are seeing or are you seeing other values for the two?
I've started a run of the PETSc test suite that compares the two values for
inconsistencies for all tests to see if I can find any problems.
Barry
Also note the importance of the reset value in KSPSetResidualHistory()
which means the values will not match when reset is PETSC_FALSE.
> On Jan 10, 2024, at 7:09 PM, Kevin G. Wang <kevi...@vt.edu> wrote:
>
> Hello everyone!
>
> I am writing a code that uses PETSc/KSP to solve linear systems. I just
> realized that after running "KSPSolve(...)", the number of iterations given
> by
>
> KSPGetIterationNumber(ksp, &numIts)
>
> is *different* from the size of the residual history given by
>
> KSPGetResidualHistory(ksp, NULL, &nEntries);
>
> That is, "numIts" is not equal to "nEntries". Is this expected, or a bug in
> my code? (I thought they should be the same...)
>
> I have tried several pairs of solvers and preconditioners (e.g., fgmres &
> bjacobi, ibcgs & bjacobi). This issue happens to all of them.
>
> Thanks!
> Kevin
>
> --
> Kevin G. Wang, Ph.D.
> Associate Professor
> Kevin T. Crofton Department of Aerospace and Ocean Engineering
> Virginia Tech
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