PetscErrorCode TSSetType(TS ts,TSType type) { PetscErrorCode (*r)(TS); PetscBool match; PetscErrorCode ierr; PetscFunctionBegin; PetscValidHeaderSpecific(ts, TS_CLASSID,1); ierr = PetscObjectTypeCompare((PetscObject) ts, type, &match);CHKERRQ(ierr); if (match) PetscFunctionReturn(0); ierr = PetscFunctionListFind(PetscObjectComm((PetscObject)ts),TSList, type,PETSC_TRUE, (void (**)(void)) &r);CHKERRQ(ierr); if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE, "Unknown TS type: %s", type); if (ts->ops->destroy) { ierr = (*(ts)->ops->destroy)(ts);CHKERRQ(ierr); ts->ops->destroy = NULL; } ierr = PetscMemzero(ts->ops,sizeof(*ts->ops));CHKERRQ(ierr); but note that PetscErrorCode (*snesfunction)(SNES,Vec,Vec,TS); PetscErrorCode (*snesjacobian)(SNES,Vec,Mat*,Mat*,MatStructure*,TS); PetscErrorCode (*prestep)(TS); PetscErrorCode (*prestage)(TS,PetscReal); PetscErrorCode (*poststep)(TS); PetscErrorCode (*setup)(TS); PetscErrorCode (*step)(TS); PetscErrorCode (*solve)(TS); PetscErrorCode (*interpolate)(TS,PetscReal,Vec); PetscErrorCode (*evaluatestep)(TS,PetscInt,Vec,PetscBool*); PetscErrorCode (*setfromoptions)(TS); PetscErrorCode (*destroy)(TS); PetscErrorCode (*view)(TS,PetscViewer); PetscErrorCode (*reset)(TS); PetscErrorCode (*linearstability)(TS,PetscReal,PetscReal,PetscReal*,PetscReal*); PetscErrorCode (*load)(TS,PetscViewer); TSOps is a combination of method specific functions and user provided functions. So if one does TSSetPostStep() before TSSetFromOptions() and then -ts_type <sometype> the post-step is wiped out even though it should not be. How to fix? Should the memzero() be replaced with something that only wipes out certain fields but preserves the pre step, prestage and post step ops. Or should those ops be moved out of TSOps and handled differently? Needs to be fixed since current behavior is cruel.