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

  6: static PetscErrorCode SNESSolve_KSPONLY(SNES snes)
  7: {
  8:   PetscErrorCode     ierr;
  9:   PetscInt           lits;
 10:   MatStructure       flg = DIFFERENT_NONZERO_PATTERN;
 11:   Vec                Y,X,F;
 12:   KSPConvergedReason kspreason;

 15:   snes->numFailures            = 0;
 16:   snes->numLinearSolveFailures = 0;
 17:   snes->reason                 = SNES_CONVERGED_ITERATING;
 18:   snes->iter                   = 0;
 19:   snes->norm                   = 0.0;

 21:   X = snes->vec_sol;
 22:   F = snes->vec_func;
 23:   Y = snes->vec_sol_update;

 25:   SNESComputeFunction(snes,X,F);
 26:   if (snes->domainerror) {
 27:     snes->reason = SNES_DIVERGED_FUNCTION_DOMAIN;
 28:     return(0);
 29:   }
 30:   if (snes->numbermonitors) {
 31:     PetscReal fnorm;
 32:     VecNorm(F,NORM_2,&fnorm);
 33:     SNESMonitor(snes,0,fnorm);
 34:   }

 36:   /* Call general purpose update function */
 37:   if (snes->ops->update) {
 38:     (*snes->ops->update)(snes, 0);
 39:   }

 41:   /* Solve J Y = F, where J is Jacobian matrix */
 42:   SNESComputeJacobian(snes,X,&snes->jacobian,&snes->jacobian_pre,&flg);
 43:   KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre,flg);
 44:   KSPSolve(snes->ksp,F,Y);
 45:   KSPGetConvergedReason(snes->ksp,&kspreason);
 46:   if (kspreason < 0 && ++snes->numLinearSolveFailures >= snes->maxLinearSolveFailures) {
 47:     PetscInfo2(snes,"iter=%D, number linear solve failures %D greater than current SNES allowed, stopping solve\n",snes->iter,snes->numLinearSolveFailures);
 48:     snes->reason = SNES_DIVERGED_LINEAR_SOLVE;
 49:   } else snes->reason = SNES_CONVERGED_ITS;

 51:   KSPGetIterationNumber(snes->ksp,&lits);
 52:   snes->linear_its += lits;
 53:   PetscInfo2(snes,"iter=%D, linear solve iterations=%D\n",snes->iter,lits);
 54:   snes->iter++;

 56:   /* Take the computed step. */
 57:   VecAXPY(X,-1.0,Y);
 58:   if (snes->numbermonitors) {
 59:     PetscReal fnorm;
 60:     SNESComputeFunction(snes,X,F);
 61:     VecNorm(F,NORM_2,&fnorm);
 62:     SNESMonitor(snes,1,fnorm);
 63:   }
 64:   return(0);
 65: }

 69: static PetscErrorCode SNESSetUp_KSPONLY(SNES snes)
 70: {

 74:   SNESSetUpMatrices(snes);
 75:   return(0);
 76: }

 80: static PetscErrorCode SNESDestroy_KSPONLY(SNES snes)
 81: {

 84:   return(0);
 85: }

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

 93:    Level: beginner

 95: .seealso:  SNESCreate(), SNES, SNESSetType(), SNESNEWTONLS, SNESNEWTONTR
 96: M*/
 99: PETSC_EXTERN PetscErrorCode SNESCreate_KSPONLY(SNES snes)
100: {

103:   snes->ops->setup          = SNESSetUp_KSPONLY;
104:   snes->ops->solve          = SNESSolve_KSPONLY;
105:   snes->ops->destroy        = SNESDestroy_KSPONLY;
106:   snes->ops->setfromoptions = 0;
107:   snes->ops->view           = 0;
108:   snes->ops->reset          = 0;

110:   snes->usesksp = PETSC_TRUE;
111:   snes->usespc  = PETSC_FALSE;

113:   snes->data = 0;
114:   return(0);
115: }