xref: /petsc/src/snes/linesearch/interface/linesearch.c (revision 7a35526ea7663f00cb6ea7142638f9b11e38a849)

#include <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.

   Collective on LineSearch

   Input Parameters:
.  comm - MPI communicator for the line search

   Output Parameters:
.  outlinesearch - the line search instance.

   Level: Beginner

   .keywords: LineSearch, Create

   .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       = 3;
  linesearch->setupcalled   = PETSC_FALSE;
  *outlinesearch            = linesearch;
  PetscFunctionReturn(0);
}

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

   Collective on LineSearch

   Input Parameters:
.  linesearch - The LineSearch instance.

   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

   Collective on SNESLineSearch

   Input Parameters:
.  linesearch - The LineSearch instance.

   Level: Intermediate

   .keywords: SNESLineSearch, Create

   .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 something.

   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 - Sets a 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.

   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.

   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

   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_ls_precheck_picard - activate this routine
-  -snes_ls_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.

   Level: Intermediate

   .keywords: SNESLineSearch, Create

   .seealso: SNESLineSearchCreate(), SNESLineSearchPreCheck(), SNESLineSearchPostCheck()
@*/
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()
@*/
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 things 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:
.   -linesearch_monitor - enables the monitor.

   Level: intermediate


.seealso: SNESLineSearchGetMonitor()
@*/
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 monitor instance for the line search

   Input Parameters:
.  linesearch - linesearch context.

   Input Parameters:
.  monitor - monitor context.

   Logically Collective on SNES


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

   Level: intermediate


.seealso: SNESLineSearchSetMonitor()
@*/
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:
+ -linesearch_type - The Line search method
. -linesearch_monitor - Print progress of line searches
. -linesearch_damping - The linesearch damping parameter.
. -linesearch_norms   - Turn on/off the linesearch norms
. -linesearch_keeplambda - Keep the previous search length as the initial guess.
- -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     *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 = PetscObjectProcessOptionsHandlers((PetscObject)linesearch);CHKERRQ(ierr);
  ierr = PetscOptionsEnd();CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "SNESLineSearchView"
/*@
   SNESLineSearchView - Views useful information for the line search.

   Input Parameters:
.  linesearch - linesearch context.

   Logically Collective on SNESLineSearch

   Level: intermediate


.seealso: SNESLineSearchCreate()
@*/
PetscErrorCode SNESLineSearchView(SNESLineSearch linesearch) {
  PetscFunctionBegin;

  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

   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()
@*/
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()
@*/
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.

   Level: intermediate

.seealso: SNESLineSearchGetSNES(), SNESLineSearchSetVecs()
@*/
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.

   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
.  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
.  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

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

   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:
.   -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 SNES

   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:
.  snes - the SNES 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

.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.

   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.

   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 func:
.   X - Projected solution

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

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

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


    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);
}