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

  6: static PetscErrorCode SNESSolve_KSPONLY(SNES snes)
  7: {
  8:   PetscErrorCode     ierr;
  9:   PetscInt           lits;
 10:   Vec                Y,X,F;


 14:   if (snes->xl || snes->xu || snes->ops->computevariablebounds) {
 15:     SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);
 16:   }

 18:   snes->numFailures            = 0;
 19:   snes->numLinearSolveFailures = 0;
 20:   snes->reason                 = SNES_CONVERGED_ITERATING;
 21:   snes->iter                   = 0;
 22:   snes->norm                   = 0.0;

 24:   X = snes->vec_sol;
 25:   F = snes->vec_func;
 26:   Y = snes->vec_sol_update;

 28:   SNESComputeFunction(snes,X,F);
 29:   if (snes->numbermonitors) {
 30:     PetscReal fnorm;
 31:     VecNorm(F,NORM_2,&fnorm);
 32:     SNESMonitor(snes,0,fnorm);
 33:   }

 35:   /* Call general purpose update function */
 36:   if (snes->ops->update) {
 37:     (*snes->ops->update)(snes, 0);
 38:   }

 40:   /* Solve J Y = F, where J is Jacobian matrix */
 41:   SNESComputeJacobian(snes,X,snes->jacobian,snes->jacobian_pre);
 42:   KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);
 43:   KSPSolve(snes->ksp,F,Y);
 44:   snes->reason = SNES_CONVERGED_ITS;
 45:   SNESCheckKSPSolve(snes);

 47:   KSPGetIterationNumber(snes->ksp,&lits);
 48:   snes->linear_its += lits;
 49:   PetscInfo2(snes,"iter=%D, linear solve iterations=%D\n",snes->iter,lits);
 50:   snes->iter++;

 52:   /* Take the computed step. */
 53:   VecAXPY(X,-1.0,Y);
 54:   SNESComputeFunction(snes,X,F);
 55:   if (snes->numbermonitors) {
 56:     PetscReal fnorm;
 57:     VecNorm(F,NORM_2,&fnorm);
 58:     SNESMonitor(snes,1,fnorm);
 59:   }
 60:   return(0);
 61: }

 65: static PetscErrorCode SNESSetUp_KSPONLY(SNES snes)
 66: {

 70:   SNESSetUpMatrices(snes);
 71:   return(0);
 72: }

 76: static PetscErrorCode SNESDestroy_KSPONLY(SNES snes)
 77: {

 80:   return(0);
 81: }

 83: /* -------------------------------------------------------------------------- */
 84: /*MC
 85:       SNESKSPONLY - Nonlinear solver that only performs one Newton step and does not compute any norms.
 86:       The main purpose of this solver is to solve linear problems using the SNES interface, without
 87:       any additional overhead in the form of vector operations.

 89:    Level: beginner

 91: .seealso:  SNESCreate(), SNES, SNESSetType(), SNESNEWTONLS, SNESNEWTONTR
 92: M*/
 95: PETSC_EXTERN PetscErrorCode SNESCreate_KSPONLY(SNES snes)
 96: {

 99:   snes->ops->setup          = SNESSetUp_KSPONLY;
100:   snes->ops->solve          = SNESSolve_KSPONLY;
101:   snes->ops->destroy        = SNESDestroy_KSPONLY;
102:   snes->ops->setfromoptions = 0;
103:   snes->ops->view           = 0;
104:   snes->ops->reset          = 0;

106:   snes->usesksp = PETSC_TRUE;
107:   snes->usespc  = PETSC_FALSE;

109:   snes->data = 0;
110:   return(0);
111: }