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

  4: static PetscErrorCode TaoLineSearchDestroy_Unit(TaoLineSearch ls)
  5: {
  6:   PetscFree(ls->data);
  7:   return 0;
  8: }

 10: static PetscErrorCode TaoLineSearchSetFromOptions_Unit(PetscOptionItems *PetscOptionsObject,TaoLineSearch ls)
 11: {
 12:   PetscOptionsHead(PetscOptionsObject,"No Unit line search options");
 13:   PetscOptionsTail();
 14:   return 0;
 15: }

 17: static PetscErrorCode TaoLineSearchView_Unit(TaoLineSearch ls,PetscViewer viewer)
 18: {
 19:   PetscBool      isascii;

 21:   PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii);
 22:   if (isascii) {
 23:     PetscViewerASCIIPrintf(viewer,"  Line Search: Unit Step.\n");
 24:   }
 25:   return 0;
 26: }

 28: static PetscErrorCode TaoLineSearchApply_Unit(TaoLineSearch ls,Vec x,PetscReal *f,Vec g,Vec step_direction)
 29: {
 30:   PetscReal      ftry;
 31:   PetscReal      startf = *f;

 33:   /* Take unit step (newx = startx + 1.0*step_direction) */
 34:   TaoLineSearchMonitor(ls, 0, *f, 0.0);
 35:   VecAXPY(x,1.0,step_direction);
 36:   TaoLineSearchComputeObjectiveAndGradient(ls,x,&ftry,g);
 37:   TaoLineSearchMonitor(ls, 1, *f, 1.0);
 38:   PetscInfo(ls,"Tao Apply Unit Step: %4.4e\n",1.0);
 39:   if (startf < ftry) {
 40:     PetscInfo(ls,"Tao Apply Unit Step, FINCREASE: F old:= %12.10e, F new: %12.10e\n",(double)startf,(double)ftry);
 41:   }
 42:   *f = ftry;
 43:   ls->step = 1.0;
 44:   ls->reason=TAOLINESEARCH_SUCCESS;
 45:   return 0;
 46: }

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

 51:    Level: developer

 53: .seealso: TaoLineSearchCreate(), TaoLineSearchSetType(), TaoLineSearchApply()

 55: .keywords: Tao, linesearch
 56: M*/
 57: PETSC_EXTERN PetscErrorCode TaoLineSearchCreate_Unit(TaoLineSearch ls)
 58: {
 59:   ls->ops->setup = NULL;
 60:   ls->ops->reset = NULL;
 61:   ls->ops->monitor = NULL;
 62:   ls->ops->apply = TaoLineSearchApply_Unit;
 63:   ls->ops->view = TaoLineSearchView_Unit;
 64:   ls->ops->destroy = TaoLineSearchDestroy_Unit;
 65:   ls->ops->setfromoptions = TaoLineSearchSetFromOptions_Unit;
 66:   return 0;
 67: }