xref: /petsc/src/snes/impls/ngmres/snesngmres.c (revision 4f02bc6a7df4e4b03c783003a8e0899ee35fcb05)

#include <../src/snes/impls/ngmres/snesngmres.h> /*I "petscsnes.h" I*/
#include <petscblaslapack.h>
#include <petscdm.h>

const char *const SNESNGMRESRestartTypes[] = {"NONE","PERIODIC","DIFFERENCE","SNESNGMRESRestartType","SNES_NGMRES_RESTART_",0};
const char *const SNESNGMRESSelectTypes[] = {"NONE","DIFFERENCE","LINESEARCH","SNESNGMRESSelectType","SNES_NGMRES_SELECT_",0};

#undef __FUNCT__
#define __FUNCT__ "SNESReset_NGMRES"
PetscErrorCode SNESReset_NGMRES(SNES snes)
{
  SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = VecDestroyVecs(ngmres->msize,&ngmres->Fdot);CHKERRQ(ierr);
  ierr = VecDestroyVecs(ngmres->msize,&ngmres->Xdot);CHKERRQ(ierr);
  ierr = SNESLineSearchDestroy(&ngmres->additive_linesearch);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESDestroy_NGMRES"
PetscErrorCode SNESDestroy_NGMRES(SNES snes)
{
  PetscErrorCode ierr;
  SNES_NGMRES    *ngmres = (SNES_NGMRES*)snes->data;

  PetscFunctionBegin;
  ierr = SNESReset_NGMRES(snes);CHKERRQ(ierr);
  ierr = PetscFree5(ngmres->h,ngmres->beta,ngmres->xi,ngmres->fnorms,ngmres->q);CHKERRQ(ierr);
  ierr = PetscFree(ngmres->s);CHKERRQ(ierr);
  ierr = PetscFree(ngmres->xnorms);CHKERRQ(ierr);
#if PETSC_USE_COMPLEX
  ierr = PetscFree(ngmres->rwork);CHKERRQ(ierr);
#endif
  ierr = PetscFree(ngmres->work);CHKERRQ(ierr);
  ierr = PetscFree(snes->data);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESSetUp_NGMRES"
PetscErrorCode SNESSetUp_NGMRES(SNES snes)
{
  SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
  const char     *optionsprefix;
  PetscInt       msize,hsize;
  PetscErrorCode ierr;
  DM             dm;

  PetscFunctionBegin;
  if (snes->pc && snes->pcside == PC_LEFT && snes->functype == SNES_FUNCTION_UNPRECONDITIONED) {
    SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"SNESNGMRES does not support left preconditioning with unpreconditioned function");
  }
  if (snes->pcside == PC_LEFT && snes->functype == SNES_FUNCTION_DEFAULT) snes->functype = SNES_FUNCTION_PRECONDITIONED;
  ierr = SNESSetWorkVecs(snes,5);CHKERRQ(ierr);

  if (!snes->vec_sol) {
    ierr             = SNESGetDM(snes,&dm);CHKERRQ(ierr);
    ierr             = DMCreateGlobalVector(dm,&snes->vec_sol);CHKERRQ(ierr);
  }

  if (!ngmres->Xdot) {ierr = VecDuplicateVecs(snes->vec_sol,ngmres->msize,&ngmres->Xdot);CHKERRQ(ierr);}
  if (!ngmres->Fdot) {ierr = VecDuplicateVecs(snes->vec_sol,ngmres->msize,&ngmres->Fdot);CHKERRQ(ierr);}
  if (!ngmres->setup_called) {
    msize = ngmres->msize;          /* restart size */
    hsize = msize * msize;

    /* explicit least squares minimization solve */
    ierr = PetscMalloc5(hsize,&ngmres->h, msize,&ngmres->beta, msize,&ngmres->xi, msize,&ngmres->fnorms, hsize,&ngmres->q);CHKERRQ(ierr);
    ierr = PetscMalloc1(msize,&ngmres->xnorms);CHKERRQ(ierr);
    ngmres->nrhs  = 1;
    ngmres->lda   = msize;
    ngmres->ldb   = msize;
    ierr          = PetscMalloc1(msize,&ngmres->s);CHKERRQ(ierr);
    ierr          = PetscMemzero(ngmres->h,   hsize*sizeof(PetscScalar));CHKERRQ(ierr);
    ierr          = PetscMemzero(ngmres->q,   hsize*sizeof(PetscScalar));CHKERRQ(ierr);
    ierr          = PetscMemzero(ngmres->xi,  msize*sizeof(PetscScalar));CHKERRQ(ierr);
    ierr          = PetscMemzero(ngmres->beta,msize*sizeof(PetscScalar));CHKERRQ(ierr);
    ngmres->lwork = 12*msize;
#if PETSC_USE_COMPLEX
    ierr = PetscMalloc1(ngmres->lwork,&ngmres->rwork);CHKERRQ(ierr);
#endif
    ierr = PetscMalloc1(ngmres->lwork,&ngmres->work);CHKERRQ(ierr);
  }

  /* linesearch setup */
  ierr = SNESGetOptionsPrefix(snes,&optionsprefix);CHKERRQ(ierr);

  if (ngmres->select_type == SNES_NGMRES_SELECT_LINESEARCH) {
    ierr = SNESLineSearchCreate(PetscObjectComm((PetscObject)snes),&ngmres->additive_linesearch);CHKERRQ(ierr);
    ierr = SNESLineSearchSetSNES(ngmres->additive_linesearch,snes);CHKERRQ(ierr);
    ierr = SNESLineSearchSetType(ngmres->additive_linesearch,SNESLINESEARCHL2);CHKERRQ(ierr);
    ierr = SNESLineSearchAppendOptionsPrefix(ngmres->additive_linesearch,"additive_");CHKERRQ(ierr);
    ierr = SNESLineSearchAppendOptionsPrefix(ngmres->additive_linesearch,optionsprefix);CHKERRQ(ierr);
    ierr = SNESLineSearchSetFromOptions(ngmres->additive_linesearch);CHKERRQ(ierr);
  }

  ngmres->setup_called = PETSC_TRUE;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESSetFromOptions_NGMRES"
PetscErrorCode SNESSetFromOptions_NGMRES(PetscOptionItems *PetscOptionsObject,SNES snes)
{
  SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
  PetscErrorCode ierr;
  PetscBool      debug = PETSC_FALSE;
  SNESLineSearch linesearch;

  PetscFunctionBegin;
  ierr = PetscOptionsHead(PetscOptionsObject,"SNES NGMRES options");CHKERRQ(ierr);
  ierr = PetscOptionsEnum("-snes_ngmres_select_type","Select type","SNESNGMRESSetSelectType",SNESNGMRESSelectTypes,
                          (PetscEnum)ngmres->select_type,(PetscEnum*)&ngmres->select_type,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsEnum("-snes_ngmres_restart_type","Restart type","SNESNGMRESSetRestartType",SNESNGMRESRestartTypes,
                          (PetscEnum)ngmres->restart_type,(PetscEnum*)&ngmres->restart_type,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_ngmres_candidate", "Use candidate storage",              "SNES",ngmres->candidate,&ngmres->candidate,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_ngmres_approxfunc","Linearly approximate the function", "SNES",ngmres->approxfunc,&ngmres->approxfunc,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-snes_ngmres_m",          "Number of directions",               "SNES",ngmres->msize,&ngmres->msize,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-snes_ngmres_restart",    "Iterations before forced restart",   "SNES",ngmres->restart_periodic,&ngmres->restart_periodic,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-snes_ngmres_restart_it", "Tolerance iterations before restart","SNES",ngmres->restart_it,&ngmres->restart_it,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_ngmres_monitor",   "Monitor actions of NGMRES",          "SNES",ngmres->monitor ? PETSC_TRUE : PETSC_FALSE,&debug,NULL);CHKERRQ(ierr);
  if (debug) {
    ngmres->monitor = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));CHKERRQ(ierr);
  }
  ierr = PetscOptionsReal("-snes_ngmres_gammaA",    "Residual selection constant",   "SNES",ngmres->gammaA,&ngmres->gammaA,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsReal("-snes_ngmres_gammaC",    "Residual restart constant",     "SNES",ngmres->gammaC,&ngmres->gammaC,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsReal("-snes_ngmres_epsilonB",  "Difference selection constant", "SNES",ngmres->epsilonB,&ngmres->epsilonB,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsReal("-snes_ngmres_deltaB",    "Difference residual selection constant", "SNES",ngmres->deltaB,&ngmres->deltaB,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_ngmres_single_reduction", "Aggregate reductions",  "SNES",ngmres->singlereduction,&ngmres->singlereduction,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_ngmres_restart_fm_rise", "Restart on F_M residual rise",  "SNESNGMRESSetRestartFmRise",ngmres->restart_fm_rise,&ngmres->restart_fm_rise,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsTail();CHKERRQ(ierr);
  if ((ngmres->gammaA > ngmres->gammaC) && (ngmres->gammaC > 2.)) ngmres->gammaC = ngmres->gammaA;

  /* set the default type of the line search if the user hasn't already. */
  if (!snes->linesearch) {
    ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
    ierr = SNESLineSearchSetType(linesearch,SNESLINESEARCHBASIC);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESView_NGMRES"
PetscErrorCode SNESView_NGMRES(SNES snes,PetscViewer viewer)
{
  SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
  PetscBool      iascii;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectTypeCompare((PetscObject) viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
  if (iascii) {
    ierr = PetscViewerASCIIPrintf(viewer,"  Number of stored past updates: %d\n", ngmres->msize);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  Residual selection: gammaA=%1.0e, gammaC=%1.0e\n",ngmres->gammaA,ngmres->gammaC);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  Difference restart: epsilonB=%1.0e, deltaB=%1.0e\n",ngmres->epsilonB,ngmres->deltaB);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  Restart on F_M residual increase: %s\n",ngmres->restart_fm_rise?"TRUE":"FALSE");CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESSolve_NGMRES"
PetscErrorCode SNESSolve_NGMRES(SNES snes)
{
  SNES_NGMRES          *ngmres = (SNES_NGMRES*) snes->data;
  /* present solution, residual, and preconditioned residual */
  Vec                  X,F,B,D,Y;

  /* candidate linear combination answers */
  Vec                  XA,FA,XM,FM;

  /* coefficients and RHS to the minimization problem */
  PetscReal            fnorm,fMnorm,fAnorm;
  PetscReal            xnorm,xMnorm,xAnorm;
  PetscReal            ynorm,yMnorm,yAnorm;
  PetscInt             k,k_restart,l,ivec,restart_count = 0;

  /* solution selection data */
  PetscBool            selectRestart;
  PetscReal            dnorm,dminnorm = 0.0;
  PetscReal            fminnorm;

  SNESConvergedReason  reason;
  SNESLineSearchReason lssucceed;
  PetscErrorCode       ierr;

  PetscFunctionBegin;
  if (snes->xl || snes->xu || snes->ops->computevariablebounds) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);

  ierr = PetscCitationsRegister(SNESCitation,&SNEScite);CHKERRQ(ierr);
  /* variable initialization */
  snes->reason = SNES_CONVERGED_ITERATING;
  X            = snes->vec_sol;
  F            = snes->vec_func;
  B            = snes->vec_rhs;
  XA           = snes->vec_sol_update;
  FA           = snes->work[0];
  D            = snes->work[1];

  /* work for the line search */
  Y  = snes->work[2];
  XM = snes->work[3];
  FM = snes->work[4];

  ierr       = PetscObjectSAWsTakeAccess((PetscObject)snes);CHKERRQ(ierr);
  snes->iter = 0;
  snes->norm = 0.;
  ierr       = PetscObjectSAWsGrantAccess((PetscObject)snes);CHKERRQ(ierr);

  /* initialization */

  if (snes->pc && snes->pcside == PC_LEFT) {
    ierr = SNESApplyNPC(snes,X,NULL,F);CHKERRQ(ierr);
    ierr = SNESGetConvergedReason(snes->pc,&reason);CHKERRQ(ierr);
    if (reason < 0  && reason != SNES_DIVERGED_MAX_IT) {
      snes->reason = SNES_DIVERGED_INNER;
      PetscFunctionReturn(0);
    }
    ierr = VecNorm(F,NORM_2,&fnorm);CHKERRQ(ierr);
  } else {
    if (!snes->vec_func_init_set) {
      ierr = SNESComputeFunction(snes,X,F);CHKERRQ(ierr);
    } else snes->vec_func_init_set = PETSC_FALSE;

    ierr = VecNorm(F,NORM_2,&fnorm);CHKERRQ(ierr);
    SNESCheckFunctionNorm(snes,fnorm);
  }
  fminnorm = fnorm;

  ierr       = PetscObjectSAWsTakeAccess((PetscObject)snes);CHKERRQ(ierr);
  snes->norm = fnorm;
  ierr       = PetscObjectSAWsGrantAccess((PetscObject)snes);CHKERRQ(ierr);
  ierr       = SNESLogConvergenceHistory(snes,fnorm,0);CHKERRQ(ierr);
  ierr       = SNESMonitor(snes,0,fnorm);CHKERRQ(ierr);
  ierr       = (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);CHKERRQ(ierr);
  if (snes->reason) PetscFunctionReturn(0);
  SNESNGMRESUpdateSubspace_Private(snes,0,0,F,fnorm,X);

  k_restart = 1;
  l         = 1;
  ivec      = 0;
  for (k=1; k < snes->max_its+1; k++) {
    /* Computation of x^M */
    if (snes->pc && snes->pcside == PC_RIGHT) {
      ierr = VecCopy(X,XM);CHKERRQ(ierr);
      ierr = SNESSetInitialFunction(snes->pc,F);CHKERRQ(ierr);

      ierr = PetscLogEventBegin(SNES_NPCSolve,snes->pc,XM,B,0);CHKERRQ(ierr);
      ierr = SNESSolve(snes->pc,B,XM);CHKERRQ(ierr);
      ierr = PetscLogEventEnd(SNES_NPCSolve,snes->pc,XM,B,0);CHKERRQ(ierr);

      ierr = SNESGetConvergedReason(snes->pc,&reason);CHKERRQ(ierr);
      if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
        snes->reason = SNES_DIVERGED_INNER;
        PetscFunctionReturn(0);
      }
      ierr = SNESGetNPCFunction(snes,FM,&fMnorm);CHKERRQ(ierr);
    } else {
      /* no preconditioner -- just take gradient descent with line search */
      ierr = VecCopy(F,Y);CHKERRQ(ierr);
      ierr = VecCopy(F,FM);CHKERRQ(ierr);
      ierr = VecCopy(X,XM);CHKERRQ(ierr);

      fMnorm = fnorm;

      ierr = SNESLineSearchApply(snes->linesearch,XM,FM,&fMnorm,Y);CHKERRQ(ierr);
      ierr = SNESLineSearchGetReason(snes->linesearch,&lssucceed);CHKERRQ(ierr);
      if (lssucceed) {
        if (++snes->numFailures >= snes->maxFailures) {
          snes->reason = SNES_DIVERGED_LINE_SEARCH;
          PetscFunctionReturn(0);
        }
      }
    }

    ierr = SNESNGMRESFormCombinedSolution_Private(snes,ivec,l,XM,FM,fMnorm,X,XA,FA);CHKERRQ(ierr);
    /* r = F(x) */
    if (fminnorm > fMnorm) fminnorm = fMnorm;  /* the minimum norm is now of F^M */

    /* differences for selection and restart */
    if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE || ngmres->select_type == SNES_NGMRES_SELECT_DIFFERENCE) {
      ierr = SNESNGMRESNorms_Private(snes,l,X,F,XM,FM,XA,FA,D,&dnorm,&dminnorm,&xMnorm,NULL,&yMnorm,&xAnorm,&fAnorm,&yAnorm);CHKERRQ(ierr);
    } else {
      ierr = SNESNGMRESNorms_Private(snes,l,X,F,XM,FM,XA,FA,D,NULL,NULL,&xMnorm,NULL,&yMnorm,&xAnorm,&fAnorm,&yAnorm);CHKERRQ(ierr);
    }
    SNESCheckFunctionNorm(snes,fnorm);

    /* combination (additive) or selection (multiplicative) of the N-GMRES solution */
    ierr          = SNESNGMRESSelect_Private(snes,k_restart,XM,FM,xMnorm,fMnorm,yMnorm,XA,FA,xAnorm,fAnorm,yAnorm,dnorm,fminnorm,dminnorm,X,F,Y,&xnorm,&fnorm,&ynorm);CHKERRQ(ierr);
    selectRestart = PETSC_FALSE;

    if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE) {
      ierr = SNESNGMRESSelectRestart_Private(snes,l,fMnorm,fAnorm,dnorm,fminnorm,dminnorm,&selectRestart);CHKERRQ(ierr);

      /* if the restart conditions persist for more than restart_it iterations, restart. */
      if (selectRestart) restart_count++;
      else restart_count = 0;
    } else if (ngmres->restart_type == SNES_NGMRES_RESTART_PERIODIC) {
      if (k_restart > ngmres->restart_periodic) {
        if (ngmres->monitor) ierr = PetscViewerASCIIPrintf(ngmres->monitor,"periodic restart after %D iterations\n",k_restart);CHKERRQ(ierr);
        restart_count = ngmres->restart_it;
      }
    }

    ivec = k_restart % ngmres->msize; /* replace the last used part of the subspace */

    /* restart after restart conditions have persisted for a fixed number of iterations */
    if (restart_count >= ngmres->restart_it) {
      if (ngmres->monitor) {
        ierr = PetscViewerASCIIPrintf(ngmres->monitor,"Restarted at iteration %d\n",k_restart);CHKERRQ(ierr);
      }
      restart_count = 0;
      k_restart     = 1;
      l             = 1;
      ivec          = 0;
      /* q_{00} = nu */
      ierr = SNESNGMRESUpdateSubspace_Private(snes,0,0,FM,fMnorm,XM);CHKERRQ(ierr);
    } else {
      /* select the current size of the subspace */
      if (l < ngmres->msize) l++;
      k_restart++;
      /* place the current entry in the list of previous entries */
      if (ngmres->candidate) {
        if (fminnorm > fMnorm) fminnorm = fMnorm;
        ierr = SNESNGMRESUpdateSubspace_Private(snes,ivec,l,FM,fMnorm,XM);CHKERRQ(ierr);
      } else {
        if (fminnorm > fnorm) fminnorm = fnorm;
        ierr = SNESNGMRESUpdateSubspace_Private(snes,ivec,l,F,fnorm,X);CHKERRQ(ierr);
      }
    }

    ierr       = PetscObjectSAWsTakeAccess((PetscObject)snes);CHKERRQ(ierr);
    snes->iter = k;
    snes->norm = fnorm;
    ierr = PetscObjectSAWsGrantAccess((PetscObject)snes);CHKERRQ(ierr);
    ierr = SNESLogConvergenceHistory(snes,snes->norm,snes->iter);CHKERRQ(ierr);
    ierr = SNESMonitor(snes,snes->iter,snes->norm);CHKERRQ(ierr);
    ierr = (*snes->ops->converged)(snes,snes->iter,0,0,fnorm,&snes->reason,snes->cnvP);CHKERRQ(ierr);
    if (snes->reason) PetscFunctionReturn(0);
  }
  snes->reason = SNES_DIVERGED_MAX_IT;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetRestartFmRise"
/*@
 SNESNGMRESSetRestartFmRise - Increase the restart count if the step x_M increases the residual F_M

  Input Parameters:
  +  snes - the SNES context.
  -  flg  - boolean value deciding whether to use the option or not

  Options Database:
  + -snes_ngmres_restart_fm_rise - Increase the restart count if the step x_M increases the residual F_M

  Level: intermediate

  Notes:
  If the proposed step x_M increases the residual F_M, it might be trying to get out of a stagnation area.
  To help the solver do that, reset the Krylov subspace whenever F_M increases.

  This option must be used with SNES_NGMRES_RESTART_DIFFERENCE

  The default is FALSE.
  .seealso: SNES_NGMRES_RESTART_DIFFERENCE
  @*/
PetscErrorCode SNESNGMRESSetRestartFmRise(SNES snes,PetscBool flg)
{
    PetscErrorCode (*f)(SNES,PetscBool);
    PetscErrorCode ierr;

    PetscFunctionBegin;
    ierr = PetscObjectQueryFunction((PetscObject)snes,"SNESNGMRESSetRestartFmRise_C",&f);CHKERRQ(ierr);
    if (f) {ierr = (f)(snes,flg);CHKERRQ(ierr);}
    PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetRestartFmRise_NGMRES"
PetscErrorCode SNESNGMRESSetRestartFmRise_NGMRES(SNES snes,PetscBool flg)
{
  SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

  PetscFunctionBegin;
  ngmres->restart_fm_rise = flg;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESGetRestartFmRise"
PetscErrorCode SNESNGMRESGetRestartFmRise(SNES snes,PetscBool *flg)
{
    PetscErrorCode (*f)(SNES,PetscBool*);
    PetscErrorCode ierr;

    PetscFunctionBegin;
    ierr = PetscObjectQueryFunction((PetscObject)snes,"SNESNGMRESGetRestartFmRise_C",&f);CHKERRQ(ierr);
    if (f) {ierr = (f)(snes,flg);CHKERRQ(ierr);}
    PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESGetRestartFmRise_NGMRES"
PetscErrorCode SNESNGMRESGetRestartFmRise_NGMRES(SNES snes,PetscBool *flg)
{
  SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

  PetscFunctionBegin;
  *flg = ngmres->restart_fm_rise;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetRestartType"
/*@
    SNESNGMRESSetRestartType - Sets the restart type for SNESNGMRES.

    Logically Collective on SNES

    Input Parameters:
+   snes - the iterative context
-   rtype - restart type

    Options Database:
+   -snes_ngmres_restart_type<difference,periodic,none> - set the restart type
-   -snes_ngmres_restart[30] - sets the number of iterations before restart for periodic

    Level: intermediate

    SNESNGMRESRestartTypes:
+   SNES_NGMRES_RESTART_NONE - never restart
.   SNES_NGMRES_RESTART_DIFFERENCE - restart based upon difference criteria
-   SNES_NGMRES_RESTART_PERIODIC - restart after a fixed number of iterations

    Notes:
    The default line search used is the L2 line search and it requires two additional function evaluations.

.keywords: SNES, SNESNGMRES, restart, type, set SNESLineSearch
@*/
PetscErrorCode SNESNGMRESSetRestartType(SNES snes,SNESNGMRESRestartType rtype)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
  ierr = PetscTryMethod(snes,"SNESNGMRESSetRestartType_C",(SNES,SNESNGMRESRestartType),(snes,rtype));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetSelectType"
/*@
    SNESNGMRESSetSelectType - Sets the selection type for SNESNGMRES.  This determines how the candidate solution and
    combined solution are used to create the next iterate.

    Logically Collective on SNES

    Input Parameters:
+   snes - the iterative context
-   stype - selection type

    Options Database:
.   -snes_ngmres_select_type<difference,none,linesearch>

    Level: intermediate

    SNESNGMRESSelectTypes:
+   SNES_NGMRES_SELECT_NONE - choose the combined solution all the time
.   SNES_NGMRES_SELECT_DIFFERENCE - choose based upon the selection criteria
-   SNES_NGMRES_SELECT_LINESEARCH - choose based upon line search combination

    Notes:
    The default line search used is the L2 line search and it requires two additional function evaluations.

.keywords: SNES, SNESNGMRES, selection, type, set SNESLineSearch
@*/
PetscErrorCode SNESNGMRESSetSelectType(SNES snes,SNESNGMRESSelectType stype)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
  ierr = PetscTryMethod(snes,"SNESNGMRESSetSelectType_C",(SNES,SNESNGMRESSelectType),(snes,stype));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetSelectType_NGMRES"
PetscErrorCode SNESNGMRESSetSelectType_NGMRES(SNES snes,SNESNGMRESSelectType stype)
{
  SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

  PetscFunctionBegin;
  ngmres->select_type = stype;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESNGMRESSetRestartType_NGMRES"
PetscErrorCode SNESNGMRESSetRestartType_NGMRES(SNES snes,SNESNGMRESRestartType rtype)
{
  SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

  PetscFunctionBegin;
  ngmres->restart_type = rtype;
  PetscFunctionReturn(0);
}

/*MC
  SNESNGMRES - The Nonlinear Generalized Minimum Residual method.

   Level: beginner

   Options Database:
+  -snes_ngmres_select_type<difference,none,linesearch> - choose the select between candidate and combined solution
.  -snes_ngmres_restart_type<difference,none,periodic> - choose the restart conditions
.  -snes_ngmres_candidate        - Use NGMRES variant which combines candidate solutions instead of actual solutions
.  -snes_ngmres_m                - Number of stored previous solutions and residuals
.  -snes_ngmres_restart_it       - Number of iterations the restart conditions hold before restart
.  -snes_ngmres_gammaA           - Residual tolerance for solution select between the candidate and combination
.  -snes_ngmres_gammaC           - Residual tolerance for restart
.  -snes_ngmres_epsilonB         - Difference tolerance between subsequent solutions triggering restart
.  -snes_ngmres_deltaB           - Difference tolerance between residuals triggering restart
.  -snes_ngmres_restart_fm_rise  - Restart on residual rise from x_M step
.  -snes_ngmres_monitor          - Prints relevant information about the ngmres iteration
.  -snes_linesearch_type <basic,l2,cp> - Line search type used for the default smoother
-  -additive_snes_linesearch_type - linesearch type used to select between the candidate and combined solution with additive select type

   Notes:

   The N-GMRES method combines m previous solutions into a minimum-residual solution by solving a small linearized
   optimization problem at each iteration.

   Very similar to the SNESANDERSON algorithm.

   References:

   C. W. Oosterlee and T. Washio, "Krylov Subspace Acceleration of Nonlinear Multigrid with Application to Recirculating Flows",
   SIAM Journal on Scientific Computing, 21(5), 2000.

   Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers",
   SIAM Review, 57(4), 2015


.seealso: SNESCreate(), SNES, SNESSetType(), SNESType (for list of available types)
M*/

#undef __FUNCT__
#define __FUNCT__ "SNESCreate_NGMRES"
PETSC_EXTERN PetscErrorCode SNESCreate_NGMRES(SNES snes)
{
  SNES_NGMRES    *ngmres;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  snes->ops->destroy        = SNESDestroy_NGMRES;
  snes->ops->setup          = SNESSetUp_NGMRES;
  snes->ops->setfromoptions = SNESSetFromOptions_NGMRES;
  snes->ops->view           = SNESView_NGMRES;
  snes->ops->solve          = SNESSolve_NGMRES;
  snes->ops->reset          = SNESReset_NGMRES;

  snes->usespc   = PETSC_TRUE;
  snes->usesksp  = PETSC_FALSE;
  snes->pcside   = PC_RIGHT;

  ierr          = PetscNewLog(snes,&ngmres);CHKERRQ(ierr);
  snes->data    = (void*) ngmres;
  ngmres->msize = 30;

  if (!snes->tolerancesset) {
    snes->max_funcs = 30000;
    snes->max_its   = 10000;
  }

  ngmres->candidate = PETSC_FALSE;

  ngmres->additive_linesearch = NULL;
  ngmres->approxfunc          = PETSC_FALSE;
  ngmres->restart_it          = 2;
  ngmres->restart_periodic    = 30;
  ngmres->gammaA              = 2.0;
  ngmres->gammaC              = 2.0;
  ngmres->deltaB              = 0.9;
  ngmres->epsilonB            = 0.1;
  ngmres->restart_fm_rise     = PETSC_FALSE;

  ngmres->restart_type = SNES_NGMRES_RESTART_DIFFERENCE;
  ngmres->select_type  = SNES_NGMRES_SELECT_DIFFERENCE;

  ierr = PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetSelectType_C",SNESNGMRESSetSelectType_NGMRES);CHKERRQ(ierr);
  ierr = PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetRestartType_C",SNESNGMRESSetRestartType_NGMRES);CHKERRQ(ierr);
  ierr = PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetRestartFmRise_C",SNESNGMRESSetRestartFmRise_NGMRES);CHKERRQ(ierr);
  ierr = PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESGetRestartFmRise_C",SNESNGMRESGetRestartFmRise_NGMRES);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}