xref: /petsc/src/snes/linesearch/interface/linesearch.c (revision 6cc8e53b32cf1654821b3e56994d9198e43a176b)

#include <petsc-private/linesearchimpl.h> /*I "petscsnes.h" I*/

PetscBool  SNESLineSearchRegisterAllCalled = PETSC_FALSE;
PetscFList SNESLineSearchList              = PETSC_NULL;

PetscClassId   SNESLINESEARCH_CLASSID;
PetscLogEvent  SNESLineSearch_Apply;

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchCreate"
/*@
   SNESLineSearchCreate - Creates the line search context.

   Logically Collective on Comm

   Input Parameters:
.  comm - MPI communicator for the line search (typically from the associated SNES context).

   Output Parameters:
.  outlinesearch - the line search instance.

   Level: Beginner

   .keywords: LineSearch, create, context

   .seealso: LineSearchDestroy()
@*/

PetscErrorCode SNESLineSearchCreate(MPI_Comm comm, SNESLineSearch *outlinesearch) {
  PetscErrorCode      ierr;
  SNESLineSearch     linesearch;
  PetscFunctionBegin;
  PetscValidPointer(outlinesearch,2);
  *outlinesearch = PETSC_NULL;
  ierr = PetscHeaderCreate(linesearch,_p_LineSearch,struct _LineSearchOps,SNESLINESEARCH_CLASSID, 0,
                           "SNESLineSearch","Line-search method","SNESLineSearch",comm,SNESLineSearchDestroy,SNESLineSearchView);CHKERRQ(ierr);

  linesearch->ops->precheckstep = PETSC_NULL;
  linesearch->ops->postcheckstep = PETSC_NULL;

  linesearch->vec_sol_new   = PETSC_NULL;
  linesearch->vec_func_new  = PETSC_NULL;
  linesearch->vec_sol       = PETSC_NULL;
  linesearch->vec_func      = PETSC_NULL;
  linesearch->vec_update    = PETSC_NULL;

  linesearch->lambda        = 1.0;
  linesearch->fnorm         = 1.0;
  linesearch->ynorm         = 1.0;
  linesearch->xnorm         = 1.0;
  linesearch->success       = PETSC_TRUE;
  linesearch->norms         = PETSC_TRUE;
  linesearch->keeplambda    = PETSC_FALSE;
  linesearch->damping       = 1.0;
  linesearch->maxstep       = 1e8;
  linesearch->steptol       = 1e-12;
  linesearch->rtol          = 1e-8;
  linesearch->atol          = 1e-15;
  linesearch->ltol          = 1e-8;
  linesearch->precheckctx   = PETSC_NULL;
  linesearch->postcheckctx  = PETSC_NULL;
  linesearch->max_its       = 1;
  linesearch->setupcalled   = PETSC_FALSE;
  *outlinesearch            = linesearch;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetUp"
/*@
   SNESLineSearchSetUp - Prepares the line search for being applied.

   Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The LineSearch instance.

   Notes:
   For most cases, this needn't be called outside of SNESLineSearchApply().
   The only current case where this is called outside of this is for the VI
   solvers, which modifies the solution and work vectors before the first call
   of SNESLineSearchApply, requiring the SNESLineSearch work vectors to be
   allocated upfront.


   Level: Intermediate

   .keywords: SNESLineSearch, SetUp

   .seealso: SNESLineSearchReset()
@*/

PetscErrorCode SNESLineSearchSetUp(SNESLineSearch linesearch) {
  PetscErrorCode ierr;
  PetscFunctionBegin;
  if (!((PetscObject)linesearch)->type_name) {
    ierr = SNESLineSearchSetType(linesearch,SNES_LINESEARCH_BASIC);CHKERRQ(ierr);
  }
  if (!linesearch->setupcalled) {
    if (!linesearch->vec_sol_new) {
      ierr = VecDuplicate(linesearch->vec_sol, &linesearch->vec_sol_new);CHKERRQ(ierr);
    }
    if (!linesearch->vec_func_new) {
      ierr = VecDuplicate(linesearch->vec_sol, &linesearch->vec_func_new);CHKERRQ(ierr);
    }
    if (linesearch->ops->setup) {
      ierr = (*linesearch->ops->setup)(linesearch);CHKERRQ(ierr);
    }
    linesearch->lambda = linesearch->damping;
    linesearch->setupcalled = PETSC_TRUE;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchReset"

/*@
   SNESLineSearchReset - Tears down the structures required for application of the SNESLineSearch

   Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The LineSearch instance.

   Level: Intermediate

   .keywords: SNESLineSearch, Reset

   .seealso: SNESLineSearchSetUp()
@*/

PetscErrorCode SNESLineSearchReset(SNESLineSearch linesearch) {
  PetscErrorCode ierr;
  PetscFunctionBegin;
  if (linesearch->ops->reset) {
    (*linesearch->ops->reset)(linesearch);
  }
  ierr = VecDestroy(&linesearch->vec_sol_new);CHKERRQ(ierr);
  ierr = VecDestroy(&linesearch->vec_func_new);CHKERRQ(ierr);

  ierr = VecDestroyVecs(linesearch->nwork, &linesearch->work);CHKERRQ(ierr);
  linesearch->nwork = 0;
  linesearch->setupcalled = PETSC_FALSE;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetPreCheck"
/*@C
   SNESLineSearchSetPreCheck - Sets a pre-check function for the line search routine.

   Logically Collective on SNESLineSearch

   Input Parameters:
+  linesearch - the SNESLineSearch context
.  func       - [optional] function evaluation routine
-  ctx        - [optional] user-defined context for private data for the
                function evaluation routine (may be PETSC_NULL)

   Calling sequence of func:
$    func (SNESLineSearch snes,Vec x,Vec y, PetscBool *changed);

+  x - solution vector
.  y - search direction vector
-  changed - flag to indicate the precheck changed x or y.

   Level: intermediate

.keywords: set, linesearch, pre-check

.seealso: SNESLineSearchSetPostCheck()
@*/
PetscErrorCode  SNESLineSearchSetPreCheck(SNESLineSearch linesearch, SNESLineSearchPreCheckFunc func,void *ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (func) linesearch->ops->precheckstep = func;
  if (ctx) linesearch->precheckctx = ctx;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetPreCheck"
/*@C
   SNESLineSearchSetPreCheck - Gets the pre-check function for the line search routine.

   Input Parameters:
.  linesearch - the SNESLineSearch context

   Output Parameters:
+  func       - [optional] function evaluation routine
-  ctx        - [optional] user-defined context for private data for the
                function evaluation routine (may be PETSC_NULL)

   Level: intermediate

.keywords: get, linesearch, pre-check

.seealso: SNESLineSearchGetPostCheck(), SNESLineSearchSetPreCheck()
@*/
PetscErrorCode  SNESLineSearchGetPreCheck(SNESLineSearch linesearch, SNESLineSearchPreCheckFunc *func,void **ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (func) *func = linesearch->ops->precheckstep;
  if (ctx) *ctx = linesearch->precheckctx;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetPostCheck"
/*@C
   SNESLineSearchSetPostCheck - Sets a post-check function for the line search routine.

   Logically Collective on SNESLineSearch

   Input Parameters:
+  linesearch - the SNESLineSearch context
.  func       - [optional] function evaluation routine
-  ctx        - [optional] user-defined context for private data for the
                function evaluation routine (may be PETSC_NULL)

   Calling sequence of func:
$    func (SNESLineSearch linesearch,Vec x, Vec w, Vec y, PetscBool *changed_w, *changed_y);

+  x - old solution vector
.  y - search direction vector
.  w - new solution vector
.  changed_y - indicates that the line search changed y.
.  changed_w - indicates that the line search changed w.

   Level: intermediate

.keywords: set, linesearch, post-check

.seealso: SNESLineSearchSetPreCheck()
@*/
PetscErrorCode  SNESLineSearchSetPostCheck(SNESLineSearch linesearch, SNESLineSearchPostCheckFunc func,void *ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (func) linesearch->ops->postcheckstep = func;
  if (ctx) linesearch->postcheckctx = ctx;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetPostCheck"
/*@C
   SNESLineSearchGetPostCheck - Gets the post-check function for the line search routine.

   Input Parameters:
.  linesearch - the SNESLineSearch context

   Output Parameters:
+  func       - [optional] function evaluation routine
-  ctx        - [optional] user-defined context for private data for the
                function evaluation routine (may be PETSC_NULL)

   Level: intermediate

.keywords: get, linesearch, post-check

.seealso: SNESLineSearchGetPreCheck(), SNESLineSearchSetPostCheck()
@*/
PetscErrorCode  SNESLineSearchGetPostCheck(SNESLineSearch linesearch, SNESLineSearchPostCheckFunc *func,void **ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (func) *func = linesearch->ops->postcheckstep;
  if (ctx) *ctx = linesearch->postcheckctx;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchPreCheck"
/*@
   SNESLineSearchPreCheck - Prepares the line search for being applied.

   Logically Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The linesearch instance.

   Output Parameters:
.  changed - Indicator if the pre-check has changed anything.

   Level: Beginner

   .keywords: SNESLineSearch, Create

   .seealso: SNESLineSearchPostCheck()
@*/
PetscErrorCode SNESLineSearchPreCheck(SNESLineSearch linesearch, PetscBool * changed)
{
  PetscErrorCode ierr;
  PetscFunctionBegin;
  *changed = PETSC_FALSE;
  if (linesearch->ops->precheckstep) {
    ierr = (*linesearch->ops->precheckstep)(linesearch, linesearch->vec_sol, linesearch->vec_update, changed, linesearch->precheckctx);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchPostCheck"
/*@
   SNESLineSearchPostCheck - Prepares the line search for being applied.

   Logically Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The linesearch instance.

   Output Parameters:
+  changed_Y - Indicator if the direction has been changed.
-  changed_W - Indicator if the solution has been changed.

   Level: Intermediate

   .keywords: SNESLineSearch, Create

   .seealso: SNESLineSearchPreCheck()
@*/
PetscErrorCode SNESLineSearchPostCheck(SNESLineSearch linesearch, PetscBool * changed_Y, PetscBool * changed_W)
{
  PetscErrorCode ierr;
  PetscFunctionBegin;
  *changed_Y = PETSC_FALSE;
  *changed_W = PETSC_FALSE;
  if (linesearch->ops->postcheckstep) {
    ierr = (*linesearch->ops->postcheckstep)(linesearch, linesearch->vec_sol, linesearch->vec_update, linesearch->vec_sol_new, changed_Y, changed_W, linesearch->postcheckctx);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchPreCheckPicard"
/*@C
   SNESLineSearchPreCheckPicard - Implements a correction that is sometimes useful to improve the convergence rate of Picard iteration

   Logically Collective on SNESLineSearch

   Input Arguments:
+  linesearch - linesearch context
.  X - base state for this step
.  Y - initial correction

   Output Arguments:
+  Y - correction, possibly modified
-  changed - flag indicating that Y was modified

   Options Database Key:
+  -snes_linesearch_precheck_picard - activate this routine
-  -snes_linesearch_precheck_picard_angle - angle

   Level: advanced

   Notes:
   This function should be passed to SNESLineSearchSetPreCheck()

   The justification for this method involves the linear convergence of a Picard iteration
   so the Picard linearization should be provided in place of the "Jacobian". This correction
   is generally not useful when using a Newton linearization.

   Reference:
   Hindmarsh and Payne (1996) Time step limits for stable solutions of the ice sheet equation, Annals of Glaciology.

.seealso: SNESLineSearchSetPreCheck()
@*/
PetscErrorCode SNESLineSearchPreCheckPicard(SNESLineSearch linesearch,Vec X,Vec Y,PetscBool *changed,void *ctx)
{
  PetscErrorCode ierr;
  PetscReal      angle = *(PetscReal*)linesearch->precheckctx;
  Vec            Ylast;
  PetscScalar    dot;

  PetscInt       iter;
  PetscReal      ynorm,ylastnorm,theta,angle_radians;
  SNES           snes;

  PetscFunctionBegin;
  ierr = SNESLineSearchGetSNES(linesearch, &snes);CHKERRQ(ierr);
  ierr = PetscObjectQuery((PetscObject)snes,"SNESLineSearchPreCheckPicard_Ylast",(PetscObject*)&Ylast);CHKERRQ(ierr);
  if (!Ylast) {
    ierr = VecDuplicate(Y,&Ylast);CHKERRQ(ierr);
    ierr = PetscObjectCompose((PetscObject)snes,"SNESLineSearchPreCheckPicard_Ylast",(PetscObject)Ylast);CHKERRQ(ierr);
    ierr = PetscObjectDereference((PetscObject)Ylast);CHKERRQ(ierr);
  }
  ierr = SNESGetIterationNumber(snes,&iter);CHKERRQ(ierr);
  if (iter < 2) {
    ierr = VecCopy(Y,Ylast);CHKERRQ(ierr);
    *changed = PETSC_FALSE;
    PetscFunctionReturn(0);
  }

  ierr = VecDot(Y,Ylast,&dot);CHKERRQ(ierr);
  ierr = VecNorm(Y,NORM_2,&ynorm);CHKERRQ(ierr);
  ierr = VecNorm(Ylast,NORM_2,&ylastnorm);CHKERRQ(ierr);
  /* Compute the angle between the vectors Y and Ylast, clip to keep inside the domain of acos() */
  theta = acos((double)PetscClipInterval(PetscAbsScalar(dot) / (ynorm * ylastnorm),-1.0,1.0));
  angle_radians = angle * PETSC_PI / 180.;
  if (PetscAbsReal(theta) < angle_radians || PetscAbsReal(theta - PETSC_PI) < angle_radians) {
    /* Modify the step Y */
    PetscReal alpha,ydiffnorm;
    ierr = VecAXPY(Ylast,-1.0,Y);CHKERRQ(ierr);
    ierr = VecNorm(Ylast,NORM_2,&ydiffnorm);CHKERRQ(ierr);
    alpha = ylastnorm / ydiffnorm;
    ierr = VecCopy(Y,Ylast);CHKERRQ(ierr);
    ierr = VecScale(Y,alpha);CHKERRQ(ierr);
    ierr = PetscInfo3(snes,"Angle %G degrees less than threshold %G, corrected step by alpha=%G\n",theta*180./PETSC_PI,angle,alpha);CHKERRQ(ierr);
  } else {
    ierr = PetscInfo2(snes,"Angle %G degrees exceeds threshold %G, no correction applied\n",theta*180./PETSC_PI,angle);CHKERRQ(ierr);
    ierr = VecCopy(Y,Ylast);CHKERRQ(ierr);
    *changed = PETSC_FALSE;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchApply"
/*@
   SNESLineSearchApply - Computes the line-search update.

   Collective on SNESLineSearch

   Input Parameters:
+  linesearch - The linesearch instance.
.  X - The current solution.
.  F - The current function.
.  fnorm - The current norm.
.  Y - The search direction.

   Output Parameters:
+  X - The new solution.
.  F - The new function.
-  fnorm - The new function norm.

   Options Database Keys:
+ -snes_linesearch_type - The Line search method
. -snes_linesearch_monitor - Print progress of line searches
. -snes_linesearch_damping - The linesearch damping parameter.
. -snes_linesearch_norms   - Turn on/off the linesearch norms
. -snes_linesearch_keeplambda - Keep the previous search length as the initial guess.
- -snes_linesearch_max_it - The number of iterations for iterative line searches.

   Notes:
   This is typically called from within a SNESSolve() implementation in order to
   help with convergence of the nonlinear method.  Various SNES types use line searches
   in different ways, but the overarching theme is that a line search is used to determine
   an optimal damping parameter of a step at each iteration of the method.  Each
   application of the line search may invoke SNESComputeFunction several times, and
   therefore may be fairly expensive.

   Level: Intermediate

   .keywords: SNESLineSearch, Create

   .seealso: SNESLineSearchCreate(), SNESLineSearchPreCheck(), SNESLineSearchPostCheck(), SNESSolve(), SNESComputeFunction()
@*/
PetscErrorCode SNESLineSearchApply(SNESLineSearch linesearch, Vec X, Vec F, PetscReal * fnorm, Vec Y) {
  PetscErrorCode ierr;
  PetscFunctionBegin;

  /* check the pointers */
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidHeaderSpecific(X,VEC_CLASSID,2);
  PetscValidHeaderSpecific(F,VEC_CLASSID,3);
  PetscValidHeaderSpecific(Y,VEC_CLASSID,4);

  linesearch->success = PETSC_TRUE;

  linesearch->vec_sol = X;
  linesearch->vec_update = Y;
  linesearch->vec_func = F;

  ierr = SNESLineSearchSetUp(linesearch);CHKERRQ(ierr);

  if (!linesearch->keeplambda)
    linesearch->lambda = linesearch->damping; /* set the initial guess to lambda */

  if (fnorm) {
    linesearch->fnorm = *fnorm;
  } else {
    ierr = VecNorm(F, NORM_2, &linesearch->fnorm);CHKERRQ(ierr);
  }

  ierr = PetscLogEventBegin(SNESLineSearch_Apply,linesearch,X,F,Y);CHKERRQ(ierr);

  ierr = (*linesearch->ops->apply)(linesearch);CHKERRQ(ierr);

  ierr = PetscLogEventEnd(SNESLineSearch_Apply,linesearch,X,F,Y);CHKERRQ(ierr);

  if (fnorm)
    *fnorm = linesearch->fnorm;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchDestroy"
/*@
   SNESLineSearchDestroy - Destroys the line search instance.

   Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The linesearch instance.

   Level: Intermediate

   .keywords: SNESLineSearch, Create

   .seealso: SNESLineSearchCreate(), SNESLineSearchReset(), SNESDestroy()
@*/
PetscErrorCode SNESLineSearchDestroy(SNESLineSearch * linesearch) {
  PetscErrorCode ierr;
  PetscFunctionBegin;
  if (!*linesearch) PetscFunctionReturn(0);
  PetscValidHeaderSpecific((*linesearch),SNESLINESEARCH_CLASSID,1);
  if (--((PetscObject)(*linesearch))->refct > 0) {*linesearch = 0; PetscFunctionReturn(0);}
  ierr = PetscObjectDepublish((*linesearch));CHKERRQ(ierr);
  ierr = SNESLineSearchReset(*linesearch);
  if ((*linesearch)->ops->destroy) {
    (*linesearch)->ops->destroy(*linesearch);
  }
  ierr = PetscViewerDestroy(&(*linesearch)->monitor);CHKERRQ(ierr);
  ierr = PetscHeaderDestroy(linesearch);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetMonitor"
/*@
   SNESLineSearchSetMonitor - Turns on/off printing useful information and debugging output about the line search.

   Input Parameters:
+  snes - nonlinear context obtained from SNESCreate()
-  flg - PETSC_TRUE to monitor the line search

   Logically Collective on SNES

   Options Database:
.   -snes_linesearch_monitor - enables the monitor.

   Level: intermediate


.seealso: SNESLineSearchGetMonitor(), PetscViewer
@*/
PetscErrorCode  SNESLineSearchSetMonitor(SNESLineSearch linesearch, PetscBool flg)
{

  PetscErrorCode ierr;
  PetscFunctionBegin;
  if (flg && !linesearch->monitor) {
    ierr = PetscViewerASCIIOpen(((PetscObject)linesearch)->comm,"stdout",&linesearch->monitor);CHKERRQ(ierr);
  } else if (!flg && linesearch->monitor) {
    ierr = PetscViewerDestroy(&linesearch->monitor);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetMonitor"
/*@
   SNESLineSearchGetMonitor - Gets the PetscViewer instance for the line search monitor.

   Input Parameters:
.  linesearch - linesearch context.

   Input Parameters:
.  monitor - monitor context.

   Logically Collective on SNES


   Options Database Keys:
.   -snes_linesearch_monitor - enables the monitor.

   Level: intermediate


.seealso: SNESLineSearchSetMonitor(), PetscViewer
@*/
PetscErrorCode  SNESLineSearchGetMonitor(SNESLineSearch linesearch, PetscViewer *monitor)
{

  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (monitor) {
    PetscValidPointer(monitor, 2);
    *monitor = linesearch->monitor;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetFromOptions"
/*@
   SNESLineSearchSetFromOptions - Sets options for the line search

   Input Parameters:
.  linesearch - linesearch context.

   Options Database Keys:
+ -snes_linesearch_type - The Line search method
. -snes_linesearch_monitor - Print progress of line searches
. -snes_linesearch_damping - The linesearch damping parameter.
. -snes_linesearch_norms   - Turn on/off the linesearch norms
. -snes_linesearch_keeplambda - Keep the previous search length as the initial guess.
. -snes_linesearch_order - The polynomial order of approximation used in the linesearch
- -snes_linesearch_max_it - The number of iterations for iterative line searches.


   Logically Collective on SNESLineSearch

   Level: intermediate


.seealso: SNESLineSearchCreate()
@*/
PetscErrorCode SNESLineSearchSetFromOptions(SNESLineSearch linesearch) {
  PetscErrorCode ierr;
  const char       *orders[] = {"linear", "quadratic", "cubic"};
  PetscInt         indx = 0;
  const char     *deft = SNES_LINESEARCH_BASIC;
  char           type[256];
  PetscBool      flg, set;
  PetscFunctionBegin;
  if (!SNESLineSearchRegisterAllCalled) {ierr = SNESLineSearchRegisterAll(PETSC_NULL);CHKERRQ(ierr);}

  ierr = PetscObjectOptionsBegin((PetscObject)linesearch);CHKERRQ(ierr);
  if (((PetscObject)linesearch)->type_name) {
    deft = ((PetscObject)linesearch)->type_name;
  }
  ierr = PetscOptionsList("-snes_linesearch_type","Line-search method","SNESLineSearchSetType",SNESLineSearchList,deft,type,256,&flg);CHKERRQ(ierr);
  if (flg) {
    ierr = SNESLineSearchSetType(linesearch,type);CHKERRQ(ierr);
  } else if (!((PetscObject)linesearch)->type_name) {
    ierr = SNESLineSearchSetType(linesearch,deft);CHKERRQ(ierr);
  }
  if (linesearch->ops->setfromoptions) {
    (*linesearch->ops->setfromoptions)(linesearch);CHKERRQ(ierr);
  }

  ierr = PetscOptionsBool("-snes_linesearch_monitor","Print progress of line searches","SNESSNESLineSearchSetMonitor",
                          linesearch->monitor ? PETSC_TRUE : PETSC_FALSE,&flg,&set);CHKERRQ(ierr);
  if (set) {ierr = SNESLineSearchSetMonitor(linesearch,flg);CHKERRQ(ierr);}

  ierr = PetscOptionsReal("-snes_linesearch_damping","Line search damping and initial step guess","SNESLineSearchSetDamping",linesearch->damping,&linesearch->damping,0);CHKERRQ(ierr);
  ierr = PetscOptionsReal("-snes_linesearch_rtol","Tolerance for iterative line search","SNESLineSearchSetRTolerance",linesearch->rtol,&linesearch->rtol,0);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_linesearch_norms","Compute final norms in line search","SNESLineSearchSetComputeNorms",linesearch->norms,&linesearch->norms,0);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-snes_linesearch_keeplambda","Use previous lambda as damping","SNESLineSearchSetKeepLambda",linesearch->keeplambda,&linesearch->keeplambda,0);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-snes_linesearch_max_it","Maximum iterations for iterative line searches","",linesearch->max_its,&linesearch->max_its,0);CHKERRQ(ierr);

  ierr = PetscOptionsBool("-snes_linesearch_precheck_picard","Use a correction that sometimes improves convergence of Picard iteration","SNESLineSearchPreCheckPicard",flg,&flg,&set);CHKERRQ(ierr);
  if (set) {
    if (flg) {
      linesearch->precheck_picard_angle = 10.; /* correction only active if angle is less than 10 degrees */
      ierr = PetscOptionsReal("-snes_linesearch_precheck_picard_angle","Maximum angle at which to activate the correction",
                              "none",linesearch->precheck_picard_angle,&linesearch->precheck_picard_angle,PETSC_NULL);CHKERRQ(ierr);
      ierr = SNESLineSearchSetPreCheck(linesearch,SNESLineSearchPreCheckPicard,&linesearch->precheck_picard_angle);CHKERRQ(ierr);
    } else {
      ierr = SNESLineSearchSetPreCheck(linesearch,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr);
    }
  }
  ierr = PetscOptionsEList("-snes_linesearch_order",  "Order of approximation", "SNESLineSearch", orders,3,orders[(PetscInt)linesearch->order],&indx,&flg);CHKERRQ(ierr);
  if (flg) {
    switch (indx) {
    case 0: linesearch->order = SNES_LINESEARCH_LINEAR;
      break;
    case 1: linesearch->order = SNES_LINESEARCH_QUADRATIC;
      break;
    case 2: linesearch->order = SNES_LINESEARCH_CUBIC;
      break;
    }
  }


  ierr = PetscObjectProcessOptionsHandlers((PetscObject)linesearch);CHKERRQ(ierr);
  ierr = PetscOptionsEnd();CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchView"
/*@
   SNESLineSearchView - Prints useful information about the line search not
   related to an individual call.

   Input Parameters:
.  linesearch - linesearch context.

   Logically Collective on SNESLineSearch

   Level: intermediate

.seealso: SNESLineSearchCreate()
@*/
PetscErrorCode SNESLineSearchView(SNESLineSearch linesearch, PetscViewer viewer) {
  PetscErrorCode ierr;
  PetscBool      iascii;
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (!viewer) {
    ierr = PetscViewerASCIIGetStdout(((PetscObject)linesearch)->comm,&viewer);CHKERRQ(ierr);
  }
  PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
  PetscCheckSameComm(linesearch,1,viewer,2);

  ierr = PetscTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
  if (iascii) {
    ierr = PetscObjectPrintClassNamePrefixType((PetscObject)linesearch,viewer,"SNESLineSearch Object");CHKERRQ(ierr);
    if (linesearch->ops->view) {
      ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
      ierr = (*linesearch->ops->view)(linesearch,viewer);CHKERRQ(ierr);
      ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
    }
    ierr = PetscViewerASCIIPrintf(viewer,"  maxstep=%G, minlambda=%G\n", linesearch->maxstep,linesearch->steptol);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%G, absolute=%G, lambda=%G\n", linesearch->rtol,linesearch->atol,linesearch->ltol);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D\n", linesearch->max_its);CHKERRQ(ierr);
    if (linesearch->ops->precheckstep) {
      if (linesearch->ops->precheckstep == SNESLineSearchPreCheckPicard) {
        ierr = PetscViewerASCIIPrintf(viewer,"  using precheck step to speed up Picard convergence\n", linesearch->max_its);CHKERRQ(ierr);
      } else {
        ierr = PetscViewerASCIIPrintf(viewer,"  using user-defined precheck step\n", linesearch->max_its);CHKERRQ(ierr);
      }
    }
    if (linesearch->ops->postcheckstep) {
      ierr = PetscViewerASCIIPrintf(viewer,"  using user-defined postcheck step\n", linesearch->max_its);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetType"
/*@C
   SNESLineSearchSetType - Sets the linesearch type

   Input Parameters:
+  linesearch - linesearch context.
-  type - The type of line search to be used

   Available Types:
+  basic - Simple damping line search.
.  bt - Backtracking line search over the L2 norm of the function.
.  l2 - Secant line search over the L2 norm of the function.
.  cp - Critical point secant line search assuming F(x) = grad G(x) for some unknown G(x).
-  shell - User provided SNESLineSearch implementation.

   Logically Collective on SNESLineSearch

   Level: intermediate


.seealso: SNESLineSearchCreate()
@*/
PetscErrorCode SNESLineSearchSetType(SNESLineSearch linesearch, const SNESLineSearchType type)
{

  PetscErrorCode ierr,(*r)(SNESLineSearch);
  PetscBool      match;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidCharPointer(type,2);

  ierr = PetscTypeCompare((PetscObject)linesearch,type,&match);CHKERRQ(ierr);
  if (match) PetscFunctionReturn(0);

  ierr =  PetscFListFind(SNESLineSearchList,((PetscObject)linesearch)->comm,type,PETSC_TRUE,(void (**)(void)) &r);CHKERRQ(ierr);
  if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested Line Search type %s",type);
  /* Destroy the previous private linesearch context */
  if (linesearch->ops->destroy) {
    ierr = (*(linesearch)->ops->destroy)(linesearch);CHKERRQ(ierr);
    linesearch->ops->destroy = PETSC_NULL;
  }
  /* Reinitialize function pointers in SNESLineSearchOps structure */
  linesearch->ops->apply          = 0;
  linesearch->ops->view           = 0;
  linesearch->ops->setfromoptions = 0;
  linesearch->ops->destroy        = 0;

  ierr = PetscObjectChangeTypeName((PetscObject)linesearch,type);CHKERRQ(ierr);
  ierr = (*r)(linesearch);CHKERRQ(ierr);
#if defined(PETSC_HAVE_AMS)
  if (PetscAMSPublishAll) {
    ierr = PetscObjectAMSPublish((PetscObject)linesearch);CHKERRQ(ierr);
  }
#endif
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetSNES"
/*@
   SNESLineSearchSetSNES - Sets the SNES for the linesearch for function evaluation

   Input Parameters:
+  linesearch - linesearch context.
-  snes - The snes instance

   Level: intermediate


.seealso: SNESLineSearchGetSNES(), SNESLineSearchSetVecs(), SNES
@*/
PetscErrorCode  SNESLineSearchSetSNES(SNESLineSearch linesearch, SNES snes){
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidHeaderSpecific(snes,SNES_CLASSID,2);
  linesearch->snes = snes;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetSNES"
/*@
   SNESLineSearchGetSNES - Gets the SNES for the linesearch for function evaluation

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
.  snes - The snes instance

   Level: intermediate

.seealso: SNESLineSearchGetSNES(), SNESLineSearchSetVecs(), SNES
@*/
PetscErrorCode  SNESLineSearchGetSNES(SNESLineSearch linesearch, SNES *snes){
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidPointer(snes, 2);
  *snes = linesearch->snes;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetLambda"
/*@
   SNESLineSearchGetLambda - Gets the last linesearch steplength discovered.

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
.  lambda - The last steplength computed during SNESLineSearchApply()

   Level: intermediate

.seealso: SNESLineSearchSetLambda(), SNESLineSearchGetDamping(), SNESLineSearchApply()
@*/
PetscErrorCode  SNESLineSearchGetLambda(SNESLineSearch linesearch,PetscReal *lambda)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidPointer(lambda, 2);
  *lambda = linesearch->lambda;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetLambda"
/*@
   SNESLineSearchSetLambda - Sets the linesearch steplength.

   Input Parameters:
+  linesearch - linesearch context.
-  lambda - The last steplength.

   Notes:
   This routine is typically used within implementations of SNESLineSearchApply
   to set the final steplength.  This routine (and SNESLineSearchGetLambda()) were
   added in order to facilitate Quasi-Newton methods that use the previous steplength
   as an inner scaling parameter.

   Level: intermediate

.seealso: SNESLineSearchGetLambda()
@*/
PetscErrorCode  SNESLineSearchSetLambda(SNESLineSearch linesearch, PetscReal lambda)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  linesearch->lambda = lambda;
  PetscFunctionReturn(0);
}

#undef  __FUNCT__
#define __FUNCT__ "SNESLineSearchGetTolerances"
/*@
   SNESLineSearchGetTolerances - Gets the tolerances for the method

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
+  steptol - The minimum steplength
.  maxstep - The maximum steplength
.  rtol    - The relative tolerance for iterative line searches
.  atol    - The absolute tolerance for iterative line searches
.  ltol    - The change in lambda tolerance for iterative line searches
-  max_it  - The maximum number of iterations of the line search

   Level: advanced

.seealso: SNESLineSearchSetTolerances()
@*/
PetscErrorCode  SNESLineSearchGetTolerances(SNESLineSearch linesearch,PetscReal *steptol,PetscReal *maxstep, PetscReal *rtol, PetscReal *atol, PetscReal *ltol, PetscInt *max_its)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (steptol) {
    PetscValidPointer(steptol, 2);
    *steptol = linesearch->steptol;
  }
  if (maxstep) {
    PetscValidPointer(maxstep, 3);
    *maxstep = linesearch->maxstep;
  }
  if (rtol) {
    PetscValidPointer(rtol, 4);
    *rtol = linesearch->rtol;
  }
  if (atol) {
    PetscValidPointer(atol, 5);
    *atol = linesearch->atol;
  }
  if (ltol) {
    PetscValidPointer(ltol, 6);
    *ltol = linesearch->ltol;
  }
  if (max_its) {
    PetscValidPointer(max_its, 7);
    *max_its = linesearch->max_its;
  }
  PetscFunctionReturn(0);
}

#undef  __FUNCT__
#define __FUNCT__ "SNESLineSearchSetTolerances"
/*@
   SNESLineSearchSetTolerances - Sets the tolerances for the method

   Input Parameters:
+  linesearch - linesearch context.
.  steptol - The minimum steplength
.  maxstep - The maximum steplength
.  rtol    - The relative tolerance for iterative line searches
.  atol    - The absolute tolerance for iterative line searches
.  ltol    - The change in lambda tolerance for iterative line searches
-  max_it  - The maximum number of iterations of the line search


   Level: advanced

.seealso: SNESLineSearchGetTolerances()
@*/
PetscErrorCode  SNESLineSearchSetTolerances(SNESLineSearch linesearch,PetscReal steptol,PetscReal maxstep, PetscReal rtol, PetscReal atol, PetscReal ltol, PetscInt max_its)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  linesearch->steptol = steptol;
  linesearch->maxstep = maxstep;
  linesearch->rtol = rtol;
  linesearch->atol = atol;
  linesearch->ltol = ltol;
  linesearch->max_its = max_its;
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetDamping"
/*@
   SNESLineSearchGetDamping - Gets the line search damping parameter.

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
.  damping - The damping parameter.

   Level: intermediate

.seealso: SNESLineSearchGetStepTolerance()
@*/

PetscErrorCode  SNESLineSearchGetDamping(SNESLineSearch linesearch,PetscReal *damping)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidPointer(damping, 2);
  *damping = linesearch->damping;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetDamping"
/*@
   SNESLineSearchSetDamping - Sets the line search damping paramter.

   Input Parameters:
.  linesearch - linesearch context.
.  damping - The damping parameter.

   Level: intermediate

   Notes:
   The basic line search merely takes the update step scaled by the damping parameter.
   The use of the damping parameter in the l2 and cp line searches is much more subtle;
   it is used as a starting point in calculating the secant step; however, the eventual
   step may be of greater length than the damping parameter.  In the bt line search it is
   used as the maximum possible step length, as the bt line search only backtracks.

.seealso: SNESLineSearchGetDamping()
@*/
PetscErrorCode  SNESLineSearchSetDamping(SNESLineSearch linesearch,PetscReal damping)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  linesearch->damping = damping;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetOrder"
/*@
   SNESLineSearchGetOrder - Gets the line search approximation order.

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
.  order - The order.

   Level: intermediate

.seealso: SNESLineSearchSetOrder()
@*/

PetscErrorCode  SNESLineSearchGetOrder(SNESLineSearch linesearch,SNESLineSearchOrder *order)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidPointer(order, 2);
  *order = linesearch->order;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetOrder"
/*@
   SNESLineSearchSetOrder - Sets the line search damping paramter.

   Input Parameters:
.  linesearch - linesearch context.
.  order - The damping parameter.

   Level: intermediate

   Notes:
   Variable orders are supported by the following line searches:
.  bt - cubic and quadratic

.seealso: SNESLineSearchGetOrder()
@*/
PetscErrorCode  SNESLineSearchSetOrder(SNESLineSearch linesearch,SNESLineSearchOrder order)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  linesearch->order = order;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetNorms"
/*@
   SNESLineSearchGetNorms - Gets the norms for for X, Y, and F.

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
+  xnorm - The norm of the current solution
.  fnorm - The norm of the current function
-  ynorm - The norm of the current update

   Notes:
   This function is mainly called from SNES implementations.

   Level: intermediate

.seealso: SNESLineSearchSetNorms() SNESLineSearchGetVecs()
@*/
PetscErrorCode  SNESLineSearchGetNorms(SNESLineSearch linesearch, PetscReal * xnorm, PetscReal * fnorm, PetscReal * ynorm)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (xnorm) {
    *xnorm = linesearch->xnorm;
  }
  if (fnorm) {
    *fnorm = linesearch->fnorm;
  }
  if (ynorm) {
    *ynorm = linesearch->ynorm;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetNorms"
/*@
   SNESLineSearchSetNorms - Gets the computed norms for for X, Y, and F.

   Input Parameters:
+  linesearch - linesearch context.
.  xnorm - The norm of the current solution
.  fnorm - The norm of the current function
-  ynorm - The norm of the current update

   Level: intermediate

.seealso: SNESLineSearchGetNorms(), SNESLineSearchSetVecs()
@*/
PetscErrorCode  SNESLineSearchSetNorms(SNESLineSearch linesearch, PetscReal xnorm, PetscReal fnorm, PetscReal ynorm)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  linesearch->xnorm = xnorm;
  linesearch->fnorm = fnorm;
  linesearch->ynorm = ynorm;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchComputeNorms"
/*@
   SNESLineSearchComputeNorms - Computes the norms of X, F, and Y.

   Input Parameters:
.  linesearch - linesearch context.

   Options Database Keys:
.   -snes_linesearch_norms - turn norm computation on or off.

   Level: intermediate

.seealso: SNESLineSearchGetNorms, SNESLineSearchSetNorms()
@*/
PetscErrorCode SNESLineSearchComputeNorms(SNESLineSearch linesearch)
{
  PetscErrorCode ierr;
  SNES snes;
  PetscFunctionBegin;
  if (linesearch->norms) {
    if (linesearch->ops->vinorm) {
      ierr = SNESLineSearchGetSNES(linesearch, &snes);CHKERRQ(ierr);
      ierr = VecNorm(linesearch->vec_sol, NORM_2, &linesearch->xnorm);CHKERRQ(ierr);
      ierr = VecNorm(linesearch->vec_update, NORM_2, &linesearch->ynorm);CHKERRQ(ierr);
      ierr = (*linesearch->ops->vinorm)(snes, linesearch->vec_func, linesearch->vec_sol, &linesearch->fnorm);CHKERRQ(ierr);
    } else {
      ierr = VecNormBegin(linesearch->vec_func,   NORM_2, &linesearch->fnorm);CHKERRQ(ierr);
      ierr = VecNormBegin(linesearch->vec_sol,    NORM_2, &linesearch->xnorm);CHKERRQ(ierr);
      ierr = VecNormBegin(linesearch->vec_update, NORM_2, &linesearch->ynorm);CHKERRQ(ierr);
      ierr = VecNormEnd(linesearch->vec_func,     NORM_2, &linesearch->fnorm);CHKERRQ(ierr);
      ierr = VecNormEnd(linesearch->vec_sol,      NORM_2, &linesearch->xnorm);CHKERRQ(ierr);
      ierr = VecNormEnd(linesearch->vec_update,   NORM_2, &linesearch->ynorm);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetVecs"
/*@
   SNESLineSearchGetVecs - Gets the vectors from the SNESLineSearch context

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
+  X - The old solution
.  F - The old function
.  Y - The search direction
.  W - The new solution
-  G - The new function

   Level: intermediate

.seealso: SNESLineSearchGetNorms(), SNESLineSearchSetVecs()
@*/
PetscErrorCode SNESLineSearchGetVecs(SNESLineSearch linesearch,Vec *X,Vec *F, Vec *Y,Vec *W,Vec *G) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (X) {
    PetscValidPointer(X, 2);
    *X = linesearch->vec_sol;
  }
  if (F) {
    PetscValidPointer(F, 3);
    *F = linesearch->vec_func;
  }
  if (Y) {
    PetscValidPointer(Y, 4);
    *Y = linesearch->vec_update;
  }
  if (W) {
    PetscValidPointer(W, 5);
    *W = linesearch->vec_sol_new;
  }
  if (G) {
    PetscValidPointer(G, 6);
    *G = linesearch->vec_func_new;
  }

  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetVecs"
/*@
   SNESLineSearchSetVecs - Sets the vectors on the SNESLineSearch context

   Input Parameters:
+  linesearch - linesearch context.
.  X - The old solution
.  F - The old function
.  Y - The search direction
.  W - The new solution
-  G - The new function

   Level: intermediate

.seealso: SNESLineSearchSetNorms(), SNESLineSearchGetVecs()
@*/
PetscErrorCode SNESLineSearchSetVecs(SNESLineSearch linesearch,Vec X,Vec F,Vec Y,Vec W, Vec G) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (X) {
    PetscValidHeaderSpecific(X,VEC_CLASSID,2);
    linesearch->vec_sol = X;
  }
  if (F) {
    PetscValidHeaderSpecific(F,VEC_CLASSID,3);
    linesearch->vec_func = F;
  }
  if (Y) {
    PetscValidHeaderSpecific(Y,VEC_CLASSID,4);
    linesearch->vec_update = Y;
  }
  if (W) {
    PetscValidHeaderSpecific(W,VEC_CLASSID,5);
    linesearch->vec_sol_new = W;
  }
  if (G) {
    PetscValidHeaderSpecific(G,VEC_CLASSID,6);
    linesearch->vec_func_new = G;
  }

  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchAppendOptionsPrefix"
/*@C
   SNESLineSearchAppendOptionsPrefix - Appends to the prefix used for searching for all
   SNES options in the database.

   Logically Collective on SNESLineSearch

   Input Parameters:
+  snes - the SNES context
-  prefix - the prefix to prepend to all option names

   Notes:
   A hyphen (-) must NOT be given at the beginning of the prefix name.
   The first character of all runtime options is AUTOMATICALLY the hyphen.

   Level: advanced

.keywords: SNESLineSearch, append, options, prefix, database

.seealso: SNESGetOptionsPrefix()
@*/
PetscErrorCode  SNESLineSearchAppendOptionsPrefix(SNESLineSearch linesearch,const char prefix[])
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  ierr = PetscObjectAppendOptionsPrefix((PetscObject)linesearch,prefix);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetOptionsPrefix"
/*@C
   SNESLineSearchGetOptionsPrefix - Sets the prefix used for searching for all
   SNESLineSearch options in the database.

   Not Collective

   Input Parameter:
.  linesearch - the SNESLineSearch context

   Output Parameter:
.  prefix - pointer to the prefix string used

   Notes: On the fortran side, the user should pass in a string 'prefix' of
   sufficient length to hold the prefix.

   Level: advanced

.keywords: SNESLineSearch, get, options, prefix, database

.seealso: SNESAppendOptionsPrefix()
@*/
PetscErrorCode  SNESLineSearchGetOptionsPrefix(SNESLineSearch linesearch,const char *prefix[])
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  ierr = PetscObjectGetOptionsPrefix((PetscObject)linesearch,prefix);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetWork"
/*@
   SNESLineSearchGetWork - Gets work vectors for the line search.

   Input Parameter:
+  linesearch - the SNESLineSearch context
-  nwork - the number of work vectors

   Level: developer

   Notes:
   This is typically called at the beginning of a SNESLineSearch or SNESLineSearchShell implementation.

.keywords: SNESLineSearch, work, vector

.seealso: SNESDefaultGetWork()
@*/
PetscErrorCode  SNESLineSearchGetWork(SNESLineSearch linesearch, PetscInt nwork)
{
  PetscErrorCode ierr;
  PetscFunctionBegin;
  if (linesearch->vec_sol) {
    ierr = VecDuplicateVecs(linesearch->vec_sol, nwork, &linesearch->work);CHKERRQ(ierr);
  } else {
    SETERRQ(((PetscObject)linesearch)->comm, PETSC_ERR_USER, "Cannot get linesearch work-vectors without setting a solution vec!");
  }
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetSuccess"
/*@
   SNESLineSearchGetSuccess - Gets the success/failure status of the last line search application

   Input Parameters:
.  linesearch - linesearch context.

   Output Parameters:
.  success - The success or failure status.

   Notes:
   This is typically called after SNESLineSearchApply in order to determine if the line-search failed
   (and set the SNES convergence accordingly).

   Level: intermediate

.seealso: SNESLineSearchSetSuccess()
@*/
PetscErrorCode  SNESLineSearchGetSuccess(SNESLineSearch linesearch, PetscBool *success)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscValidPointer(success, 2);
  if (success) {
    *success = linesearch->success;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetSuccess"
/*@
   SNESLineSearchSetSuccess - Sets the success/failure status of the last line search application

   Input Parameters:
+  linesearch - linesearch context.
-  success - The success or failure status.

   Notes:
   This is typically called in a SNESLineSearchApply() or SNESLineSearchShell implementation to set
   the success or failure of the line search method.

   Level: intermediate

.seealso: SNESLineSearchGetSuccess()
@*/
PetscErrorCode  SNESLineSearchSetSuccess(SNESLineSearch linesearch, PetscBool success)
{
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  PetscFunctionBegin;
  linesearch->success = success;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchSetVIFunctions"
/*@C
   SNESLineSearchSetVIFunctions - Sets VI-specific functions for line search computation.

   Input Parameters:
+  snes - nonlinear context obtained from SNESCreate()
.  projectfunc - function for projecting the function to the bounds
-  normfunc - function for computing the norm of an active set

   Logically Collective on SNES

   Calling sequence of projectfunc:
.vb
   projectfunc (SNES snes, Vec X)
.ve

    Input parameters for projectfunc:
+   snes - nonlinear context
-   X - current solution

    Output parameters for projectfunc:
.   X - Projected solution

   Calling sequence of normfunc:
.vb
   projectfunc (SNES snes, Vec X, Vec F, PetscScalar * fnorm)
.ve

    Input parameters for normfunc:
+   snes - nonlinear context
.   X - current solution
-   F - current residual

    Output parameters for normfunc:
.   fnorm - VI-specific norm of the function

    Notes:
    The VI solvers require projection of the solution to the feasible set.  projectfunc should implement this.

    The VI solvers require special evaluation of the function norm such that the norm is only calculated
    on the inactive set.  This should be implemented by normfunc.

    Level: developer

.keywords: SNES, line search, VI, nonlinear, set, line search

.seealso: SNESLineSearchGetVIFunctions(), SNESLineSearchSetPostCheck(), SNESLineSearchSetPreCheck()
@*/
extern PetscErrorCode SNESLineSearchSetVIFunctions(SNESLineSearch linesearch, SNESLineSearchVIProjectFunc projectfunc, SNESLineSearchVINormFunc normfunc)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(linesearch,SNESLINESEARCH_CLASSID,1);
  if (projectfunc) linesearch->ops->viproject = projectfunc;
  if (normfunc) linesearch->ops->vinorm = normfunc;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchGetVIFunctions"
/*@C
   SNESLineSearchGetVIFunctions - Sets VI-specific functions for line search computation.

   Input Parameters:
.  snes - nonlinear context obtained from SNESCreate()

   Output Parameters:
+  projectfunc - function for projecting the function to the bounds
-  normfunc - function for computing the norm of an active set

   Logically Collective on SNES

    Level: developer

.keywords: SNES, line search, VI, nonlinear, get, line search

.seealso: SNESLineSearchSetVIFunctions(), SNESLineSearchGetPostCheck(), SNESLineSearchGetPreCheck()
@*/
extern PetscErrorCode SNESLineSearchGetVIFunctions(SNESLineSearch linesearch, SNESLineSearchVIProjectFunc *projectfunc, SNESLineSearchVINormFunc *normfunc)
{
  PetscFunctionBegin;
  if (projectfunc) *projectfunc = linesearch->ops->viproject;
  if (normfunc) *normfunc = linesearch->ops->vinorm;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchRegister"
/*@C
  SNESLineSearchRegister - See SNESLineSearchRegisterDynamic()

  Level: advanced
@*/
PetscErrorCode  SNESLineSearchRegister(const char sname[],const char path[],const char name[],PetscErrorCode (*function)(SNESLineSearch))
{
  char           fullname[PETSC_MAX_PATH_LEN];
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscFListConcat(path,name,fullname);CHKERRQ(ierr);
  ierr = PetscFListAdd(&SNESLineSearchList,sname,fullname,(void (*)(void))function);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}