PETSc version 3.15.4
Lags the residual norm calculation so that it is computed as part of the MPI_Allreduce() for computing the inner products for the next iteration. This can reduce communication costs at the expense of doing one additional iteration.
PetscErrorCode KSPSetLagNorm(KSP ksp,PetscBool flg)
Logically Collective on ksp
Options Database Keys
|-ksp_lag_norm ||- lag the calculated residual norm
Currently only works with KSPIBCGS.
Use KSPSetNormType(ksp,KSP_NORM_NONE) to never check the norm
If you lag the norm and run with, for example, -ksp_monitor, the residual norm reported will be the lagged one.
KSPSetUp(), KSPSolve(), KSPDestroy(), KSPConvergedSkip(), KSPSetNormType(), KSPSetCheckNormIteration()
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages