[petsc-users] KSP number of iterations different from size of residual array

[Kevin G. Wang]

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
1600 Innovation Dr., VTSS Rm 224H, Blacksburg, VA 24061
Office: (540) 231-7547  |  Mobile: (650) 862-2663
URL: https://www.aoe.vt.edu/people/faculty/wang.html
Codes: https://github.com/kevinwgy
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