1: #include <petsc/private/taolinesearchimpl.h>

  3: static PetscErrorCode TaoLineSearchDestroy_Unit(TaoLineSearch ls)
  4: {
  5:   PetscFunctionBegin;
  6:   PetscFunctionReturn(PETSC_SUCCESS);
  7: }

  9: static PetscErrorCode TaoLineSearchSetFromOptions_Unit(TaoLineSearch ls, PetscOptionItems *PetscOptionsObject)
 10: {
 11:   PetscFunctionBegin;
 12:   PetscFunctionReturn(PETSC_SUCCESS);
 13: }

 15: static PetscErrorCode TaoLineSearchView_Unit(TaoLineSearch ls, PetscViewer viewer)
 16: {
 17:   PetscBool isascii;

 19:   PetscFunctionBegin;
 20:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii));
 21:   if (isascii) PetscCall(PetscViewerASCIIPrintf(viewer, "  Line Search: Unit Step %g.\n", (double)ls->initstep));
 22:   PetscFunctionReturn(PETSC_SUCCESS);
 23: }

 25: /* Take unit step (newx = startx + initstep*step_direction) */
 26: static PetscErrorCode TaoLineSearchApply_Unit(TaoLineSearch ls, Vec x, PetscReal *f, Vec g, Vec step_direction)
 27: {
 28:   PetscFunctionBegin;
 29:   PetscCall(TaoLineSearchMonitor(ls, 0, *f, 0.0));
 30:   ls->step = ls->initstep;
 31:   PetscCall(VecAXPY(x, ls->step, step_direction));
 32:   PetscCall(TaoLineSearchComputeObjectiveAndGradient(ls, x, f, g));
 33:   PetscCall(TaoLineSearchMonitor(ls, 1, *f, ls->step));
 34:   ls->reason = TAOLINESEARCH_SUCCESS;
 35:   PetscFunctionReturn(PETSC_SUCCESS);
 36: }

 38: /*MC
 39:    TAOLINESEARCHUNIT - Line-search type that disables line search and accepts the unit step length every time

 41:   Options Database Keys:
 42: . -tao_ls_stepinit <step> - steplength

 44:    Level: developer

 46: .seealso: `Tao`, `TaoLinesearch`, `TaoLineSearchCreate()`, `TaoLineSearchSetType()`, `TaoLineSearchApply()`
 47: M*/
 48: PETSC_EXTERN PetscErrorCode TaoLineSearchCreate_Unit(TaoLineSearch ls)
 49: {
 50:   PetscFunctionBegin;
 51:   ls->ops->setup          = NULL;
 52:   ls->ops->reset          = NULL;
 53:   ls->ops->monitor        = NULL;
 54:   ls->ops->apply          = TaoLineSearchApply_Unit;
 55:   ls->ops->view           = TaoLineSearchView_Unit;
 56:   ls->ops->destroy        = TaoLineSearchDestroy_Unit;
 57:   ls->ops->setfromoptions = TaoLineSearchSetFromOptions_Unit;
 58:   PetscFunctionReturn(PETSC_SUCCESS);
 59: }