ts/interface/ts.c

/* $Id: ts.c,v 1.43 2001/09/07 20:12:01 bsmith Exp $ */
#include "src/ts/tsimpl.h"        /*I "petscts.h"  I*/

/* Logging support */
int TS_COOKIE;
int TS_Step, TS_PseudoComputeTimeStep, TS_FunctionEval, TS_JacobianEval;

#undef __FUNCT__
#define __FUNCT__ "TSComputeRHSJacobian"
/*@
   TSComputeRHSJacobian - Computes the Jacobian matrix that has been
      set with TSSetRHSJacobian().

   Collective on TS and Vec

   Input Parameters:
+  ts - the SNES context
.  t - current timestep
-  x - input vector

   Output Parameters:
+  A - Jacobian matrix
.  B - optional preconditioning matrix
-  flag - flag indicating matrix structure

   Notes:
   Most users should not need to explicitly call this routine, as it
   is used internally within the nonlinear solvers.

   See SLESSetOperators() for important information about setting the
   flag parameter.

   TSComputeJacobian() is valid only for TS_NONLINEAR

   Level: developer

.keywords: SNES, compute, Jacobian, matrix

.seealso:  TSSetRHSJacobian(), SLESSetOperators()
@*/
int TSComputeRHSJacobian(TS ts,PetscReal t,Vec X,Mat *A,Mat *B,MatStructure *flg)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  PetscValidHeaderSpecific(X,VEC_COOKIE);
  PetscCheckSameComm(ts,X);
  if (ts->problem_type != TS_NONLINEAR) {
    SETERRQ(PETSC_ERR_ARG_WRONG,"For TS_NONLINEAR only");
  }
  if (ts->ops->rhsjacobian) {
    ierr = PetscLogEventBegin(TS_JacobianEval,ts,X,*A,*B);CHKERRQ(ierr);
    *flg = DIFFERENT_NONZERO_PATTERN;
    PetscStackPush("TS user Jacobian function");
    ierr = (*ts->ops->rhsjacobian)(ts,t,X,A,B,flg,ts->jacP);CHKERRQ(ierr);
    PetscStackPop;
    ierr = PetscLogEventEnd(TS_JacobianEval,ts,X,*A,*B);CHKERRQ(ierr);
    /* make sure user returned a correct Jacobian and preconditioner */
    PetscValidHeaderSpecific(*A,MAT_COOKIE);
    PetscValidHeaderSpecific(*B,MAT_COOKIE);
  } else {
    ierr = MatAssemblyBegin(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
    ierr = MatAssemblyEnd(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
    if (*A != *B) {
      ierr = MatAssemblyBegin(*B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
      ierr = MatAssemblyEnd(*B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSComputeRHSFunction"
/*
   TSComputeRHSFunction - Evaluates the right-hand-side function.

   Note: If the user did not provide a function but merely a matrix,
   this routine applies the matrix.
*/
int TSComputeRHSFunction(TS ts,PetscReal t,Vec x,Vec y)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  PetscValidHeader(x);
  PetscValidHeader(y);

  ierr = PetscLogEventBegin(TS_FunctionEval,ts,x,y,0);CHKERRQ(ierr);
  if (ts->ops->rhsfunction) {
    PetscStackPush("TS user right-hand-side function");
    ierr = (*ts->ops->rhsfunction)(ts,t,x,y,ts->funP);CHKERRQ(ierr);
    PetscStackPop;
  } else {
    if (ts->ops->rhsmatrix) { /* assemble matrix for this timestep */
      MatStructure flg;
      PetscStackPush("TS user right-hand-side matrix function");
      ierr = (*ts->ops->rhsmatrix)(ts,t,&ts->A,&ts->B,&flg,ts->jacP);CHKERRQ(ierr);
      PetscStackPop;
    }
    ierr = MatMult(ts->A,x,y);CHKERRQ(ierr);
  }

  /* apply user-provided boundary conditions (only needed if these are time dependent) */
  ierr = TSComputeRHSBoundaryConditions(ts,t,y);CHKERRQ(ierr);
  ierr = PetscLogEventEnd(TS_FunctionEval,ts,x,y,0);CHKERRQ(ierr);

  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetRHSFunction"
/*@C
    TSSetRHSFunction - Sets the routine for evaluating the function,
    F(t,u), where U_t = F(t,u).

    Collective on TS

    Input Parameters:
+   ts - the TS context obtained from TSCreate()
.   f - routine for evaluating the right-hand-side function
-   ctx - [optional] user-defined context for private data for the
          function evaluation routine (may be PETSC_NULL)

    Calling sequence of func:
$     func (TS ts,PetscReal t,Vec u,Vec F,void *ctx);

+   t - current timestep
.   u - input vector
.   F - function vector
-   ctx - [optional] user-defined function context

    Important:
    The user MUST call either this routine or TSSetRHSMatrix().

    Level: beginner

.keywords: TS, timestep, set, right-hand-side, function

.seealso: TSSetRHSMatrix()
@*/
int TSSetRHSFunction(TS ts,int (*f)(TS,PetscReal,Vec,Vec,void*),void *ctx)
{
  PetscFunctionBegin;

  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (ts->problem_type == TS_LINEAR) {
    SETERRQ(PETSC_ERR_ARG_WRONG,"Cannot set function for linear problem");
  }
  ts->ops->rhsfunction = f;
  ts->funP             = ctx;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetRHSMatrix"
/*@C
   TSSetRHSMatrix - Sets the function to compute the matrix A, where U_t = A(t) U.
   Also sets the location to store A.

   Collective on TS

   Input Parameters:
+  ts  - the TS context obtained from TSCreate()
.  A   - matrix
.  B   - preconditioner matrix (usually same as A)
.  f   - the matrix evaluation routine; use PETSC_NULL (PETSC_NULL_FUNCTION in fortran)
         if A is not a function of t.
-  ctx - [optional] user-defined context for private data for the
          matrix evaluation routine (may be PETSC_NULL)

   Calling sequence of func:
$     func (TS ts,PetscReal t,Mat *A,Mat *B,int *flag,void *ctx);

+  t - current timestep
.  A - matrix A, where U_t = A(t) U
.  B - preconditioner matrix, usually the same as A
.  flag - flag indicating information about the preconditioner matrix
          structure (same as flag in SLESSetOperators())
-  ctx - [optional] user-defined context for matrix evaluation routine

   Notes:
   See SLESSetOperators() for important information about setting the flag
   output parameter in the routine func().  Be sure to read this information!

   The routine func() takes Mat * as the matrix arguments rather than Mat.
   This allows the matrix evaluation routine to replace A and/or B with a
   completely new new matrix structure (not just different matrix elements)
   when appropriate, for instance, if the nonzero structure is changing
   throughout the global iterations.

   Important:
   The user MUST call either this routine or TSSetRHSFunction().

   Level: beginner

.keywords: TS, timestep, set, right-hand-side, matrix

.seealso: TSSetRHSFunction()
@*/
int TSSetRHSMatrix(TS ts,Mat A,Mat B,int (*f)(TS,PetscReal,Mat*,Mat*,MatStructure*,void*),void *ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  PetscValidHeaderSpecific(A,MAT_COOKIE);
  PetscValidHeaderSpecific(B,MAT_COOKIE);
  PetscCheckSameComm(ts,A);
  PetscCheckSameComm(ts,B);
  if (ts->problem_type == TS_NONLINEAR) {
    SETERRQ(PETSC_ERR_ARG_WRONG,"Not for nonlinear problems; use TSSetRHSJacobian()");
  }

  ts->ops->rhsmatrix = f;
  ts->jacP           = ctx;
  ts->A              = A;
  ts->B              = B;

  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetRHSJacobian"
/*@C
   TSSetRHSJacobian - Sets the function to compute the Jacobian of F,
   where U_t = F(U,t), as well as the location to store the matrix.

   Collective on TS

   Input Parameters:
+  ts  - the TS context obtained from TSCreate()
.  A   - Jacobian matrix
.  B   - preconditioner matrix (usually same as A)
.  f   - the Jacobian evaluation routine
-  ctx - [optional] user-defined context for private data for the
         Jacobian evaluation routine (may be PETSC_NULL)

   Calling sequence of func:
$     func (TS ts,PetscReal t,Vec u,Mat *A,Mat *B,MatStructure *flag,void *ctx);

+  t - current timestep
.  u - input vector
.  A - matrix A, where U_t = A(t)u
.  B - preconditioner matrix, usually the same as A
.  flag - flag indicating information about the preconditioner matrix
          structure (same as flag in SLESSetOperators())
-  ctx - [optional] user-defined context for matrix evaluation routine

   Notes:
   See SLESSetOperators() for important information about setting the flag
   output parameter in the routine func().  Be sure to read this information!

   The routine func() takes Mat * as the matrix arguments rather than Mat.
   This allows the matrix evaluation routine to replace A and/or B with a
   completely new new matrix structure (not just different matrix elements)
   when appropriate, for instance, if the nonzero structure is changing
   throughout the global iterations.

   Level: beginner

.keywords: TS, timestep, set, right-hand-side, Jacobian

.seealso: TSDefaultComputeJacobianColor(),
          SNESDefaultComputeJacobianColor()

@*/
int TSSetRHSJacobian(TS ts,Mat A,Mat B,int (*f)(TS,PetscReal,Vec,Mat*,Mat*,MatStructure*,void*),void *ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  PetscValidHeaderSpecific(A,MAT_COOKIE);
  PetscValidHeaderSpecific(B,MAT_COOKIE);
  PetscCheckSameComm(ts,A);
  PetscCheckSameComm(ts,B);
  if (ts->problem_type != TS_NONLINEAR) {
    SETERRQ(PETSC_ERR_ARG_WRONG,"Not for linear problems; use TSSetRHSMatrix()");
  }

  ts->ops->rhsjacobian = f;
  ts->jacP             = ctx;
  ts->A                = A;
  ts->B                = B;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSComputeRHSBoundaryConditions"
/*
   TSComputeRHSBoundaryConditions - Evaluates the boundary condition function.

   Note: If the user did not provide a function but merely a matrix,
   this routine applies the matrix.
*/
int TSComputeRHSBoundaryConditions(TS ts,PetscReal t,Vec x)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  PetscValidHeader(x);
  PetscCheckSameComm(ts,x);

  if (ts->ops->rhsbc) {
    PetscStackPush("TS user boundary condition function");
    ierr = (*ts->ops->rhsbc)(ts,t,x,ts->bcP);CHKERRQ(ierr);
    PetscStackPop;
    PetscFunctionReturn(0);
  }

  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetRHSBoundaryConditions"
/*@C
    TSSetRHSBoundaryConditions - Sets the routine for evaluating the function,
    boundary conditions for the function F.

    Collective on TS

    Input Parameters:
+   ts - the TS context obtained from TSCreate()
.   f - routine for evaluating the boundary condition function
-   ctx - [optional] user-defined context for private data for the
          function evaluation routine (may be PETSC_NULL)

    Calling sequence of func:
$     func (TS ts,PetscReal t,Vec F,void *ctx);

+   t - current timestep
.   F - function vector
-   ctx - [optional] user-defined function context

    Level: intermediate

.keywords: TS, timestep, set, boundary conditions, function
@*/
int TSSetRHSBoundaryConditions(TS ts,int (*f)(TS,PetscReal,Vec,void*),void *ctx)
{
  PetscFunctionBegin;

  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (ts->problem_type != TS_LINEAR) {
    SETERRQ(PETSC_ERR_ARG_WRONG,"For linear problems only");
  }
  ts->ops->rhsbc = f;
  ts->bcP        = ctx;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSView"
/*@C
    TSView - Prints the TS data structure.

    Collective on TS

    Input Parameters:
+   ts - the TS context obtained from TSCreate()
-   viewer - visualization context

    Options Database Key:
.   -ts_view - calls TSView() at end of TSStep()

    Notes:
    The available visualization contexts include
+     PETSC_VIEWER_STDOUT_SELF - standard output (default)
-     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
         output where only the first processor opens
         the file.  All other processors send their
         data to the first processor to print.

    The user can open an alternative visualization context with
    PetscViewerASCIIOpen() - output to a specified file.

    Level: beginner

.keywords: TS, timestep, view

.seealso: PetscViewerASCIIOpen()
@*/
int TSView(TS ts,PetscViewer viewer)
{
  int        ierr;
  char       *type;
  PetscTruth isascii,isstring;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (!viewer) viewer = PETSC_VIEWER_STDOUT_(ts->comm);
  PetscValidHeaderSpecific(viewer,PETSC_VIEWER_COOKIE);
  PetscCheckSameComm(ts,viewer);

  ierr = PetscTypeCompare((PetscObject)viewer,PETSC_VIEWER_ASCII,&isascii);CHKERRQ(ierr);
  ierr = PetscTypeCompare((PetscObject)viewer,PETSC_VIEWER_STRING,&isstring);CHKERRQ(ierr);
  if (isascii) {
    ierr = PetscViewerASCIIPrintf(viewer,"TS Object:\n");CHKERRQ(ierr);
    ierr = TSGetType(ts,(TSType *)&type);CHKERRQ(ierr);
    if (type) {
      ierr = PetscViewerASCIIPrintf(viewer,"  type: %s\n",type);CHKERRQ(ierr);
    } else {
      ierr = PetscViewerASCIIPrintf(viewer,"  type: not yet set\n");CHKERRQ(ierr);
    }
    if (ts->ops->view) {
      ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
      ierr = (*ts->ops->view)(ts,viewer);CHKERRQ(ierr);
      ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
    }
    ierr = PetscViewerASCIIPrintf(viewer,"  maximum steps=%d\n",ts->max_steps);CHKERRQ(ierr);
    ierr = PetscViewerASCIIPrintf(viewer,"  maximum time=%g\n",ts->max_time);CHKERRQ(ierr);
    if (ts->problem_type == TS_NONLINEAR) {
      ierr = PetscViewerASCIIPrintf(viewer,"  total number of nonlinear solver iterations=%d\n",ts->nonlinear_its);CHKERRQ(ierr);
    }
    ierr = PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%d\n",ts->linear_its);CHKERRQ(ierr);
  } else if (isstring) {
    ierr = TSGetType(ts,(TSType *)&type);CHKERRQ(ierr);
    ierr = PetscViewerStringSPrintf(viewer," %-7.7s",type);CHKERRQ(ierr);
  }
  ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
  if (ts->sles) {ierr = SLESView(ts->sles,viewer);CHKERRQ(ierr);}
  if (ts->snes) {ierr = SNESView(ts->snes,viewer);CHKERRQ(ierr);}
  ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}


#undef __FUNCT__
#define __FUNCT__ "TSSetApplicationContext"
/*@C
   TSSetApplicationContext - Sets an optional user-defined context for
   the timesteppers.

   Collective on TS

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
-  usrP - optional user context

   Level: intermediate

.keywords: TS, timestep, set, application, context

.seealso: TSGetApplicationContext()
@*/
int TSSetApplicationContext(TS ts,void *usrP)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->user = usrP;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetApplicationContext"
/*@C
    TSGetApplicationContext - Gets the user-defined context for the
    timestepper.

    Not Collective

    Input Parameter:
.   ts - the TS context obtained from TSCreate()

    Output Parameter:
.   usrP - user context

    Level: intermediate

.keywords: TS, timestep, get, application, context

.seealso: TSSetApplicationContext()
@*/
int TSGetApplicationContext(TS ts,void **usrP)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *usrP = ts->user;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetTimeStepNumber"
/*@
   TSGetTimeStepNumber - Gets the current number of timesteps.

   Not Collective

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  iter - number steps so far

   Level: intermediate

.keywords: TS, timestep, get, iteration, number
@*/
int TSGetTimeStepNumber(TS ts,int* iter)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *iter = ts->steps;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetInitialTimeStep"
/*@
   TSSetInitialTimeStep - Sets the initial timestep to be used,
   as well as the initial time.

   Collective on TS

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
.  initial_time - the initial time
-  time_step - the size of the timestep

   Level: intermediate

.seealso: TSSetTimeStep(), TSGetTimeStep()

.keywords: TS, set, initial, timestep
@*/
int TSSetInitialTimeStep(TS ts,PetscReal initial_time,PetscReal time_step)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->time_step         = time_step;
  ts->initial_time_step = time_step;
  ts->ptime             = initial_time;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetTimeStep"
/*@
   TSSetTimeStep - Allows one to reset the timestep at any time,
   useful for simple pseudo-timestepping codes.

   Collective on TS

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
-  time_step - the size of the timestep

   Level: intermediate

.seealso: TSSetInitialTimeStep(), TSGetTimeStep()

.keywords: TS, set, timestep
@*/
int TSSetTimeStep(TS ts,PetscReal time_step)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->time_step = time_step;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetTimeStep"
/*@
   TSGetTimeStep - Gets the current timestep size.

   Not Collective

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  dt - the current timestep size

   Level: intermediate

.seealso: TSSetInitialTimeStep(), TSGetTimeStep()

.keywords: TS, get, timestep
@*/
int TSGetTimeStep(TS ts,PetscReal* dt)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *dt = ts->time_step;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetSolution"
/*@C
   TSGetSolution - Returns the solution at the present timestep. It
   is valid to call this routine inside the function that you are evaluating
   in order to move to the new timestep. This vector not changed until
   the solution at the next timestep has been calculated.

   Not Collective, but Vec returned is parallel if TS is parallel

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  v - the vector containing the solution

   Level: intermediate

.seealso: TSGetTimeStep()

.keywords: TS, timestep, get, solution
@*/
int TSGetSolution(TS ts,Vec *v)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *v = ts->vec_sol_always;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSPublish_Petsc"
static int TSPublish_Petsc(PetscObject obj)
{
#if defined(PETSC_HAVE_AMS)
  TS   v = (TS) obj;
  int  ierr;
#endif

  PetscFunctionBegin;

#if defined(PETSC_HAVE_AMS)
  /* if it is already published then return */
  if (v->amem >=0) PetscFunctionReturn(0);

  ierr = PetscObjectPublishBaseBegin(obj);CHKERRQ(ierr);
  ierr = AMS_Memory_add_field((AMS_Memory)v->amem,"Step",&v->steps,1,AMS_INT,AMS_READ,
                                AMS_COMMON,AMS_REDUCT_UNDEF);CHKERRQ(ierr);
  ierr = AMS_Memory_add_field((AMS_Memory)v->amem,"Time",&v->ptime,1,AMS_DOUBLE,AMS_READ,
                                AMS_COMMON,AMS_REDUCT_UNDEF);CHKERRQ(ierr);
  ierr = AMS_Memory_add_field((AMS_Memory)v->amem,"CurrentTimeStep",&v->time_step,1,
                               AMS_DOUBLE,AMS_READ,AMS_COMMON,AMS_REDUCT_UNDEF);CHKERRQ(ierr);
  ierr = PetscObjectPublishBaseEnd(obj);CHKERRQ(ierr);
#endif
  PetscFunctionReturn(0);
}

/* -----------------------------------------------------------*/

#undef __FUNCT__
#define __FUNCT__ "TSCreate"
/*@C
   TSCreate - Creates a timestepper context.

   Collective on MPI_Comm

   Input Parameter:
+  comm - MPI communicator
-  type - One of  TS_LINEAR,TS_NONLINEAR
   where these types refer to problems of the forms
.vb
         U_t = A U
         U_t = A(t) U
         U_t = F(t,U)
.ve

   Output Parameter:
.  ts - the new TS context

   Level: beginner

.keywords: TS, timestep, create, context

.seealso: TSSetUp(), TSStep(), TSDestroy(), TSProblemType, TS
@*/
int TSCreate(MPI_Comm comm, TSProblemType problemtype, TS *ts)
{
  TS  t;
  int ierr;

  PetscFunctionBegin;
  PetscValidPointer(ts);
  *ts = PETSC_NULL;
#ifndef PETSC_USE_DYNAMIC_LIBRARIES
  ierr = TSInitializePackage(PETSC_NULL);                                                                 CHKERRQ(ierr);
#endif

  PetscHeaderCreate(t, _p_TS, struct _TSOps, TS_COOKIE, -1, "TS", comm, TSDestroy, TSView);
  PetscLogObjectCreate(t);
  PetscLogObjectMemory(t, sizeof(struct _p_TS));
  ierr = PetscMemzero(t->ops, sizeof(struct _TSOps));                                                     CHKERRQ(ierr);
  t->bops->publish      = TSPublish_Petsc;
  t->type_name          = PETSC_NULL;

  t->problem_type       = problemtype;
  t->vec_sol            = PETSC_NULL;
  t->vec_sol_always     = PETSC_NULL;
  t->numbermonitors     = 0;
  t->isGTS              = PETSC_FALSE;
  t->isExplicit         = PETSC_NULL;
  t->Iindex             = PETSC_NULL;
  t->sles               = PETSC_NULL;
  t->A                  = PETSC_NULL;
  t->B                  = PETSC_NULL;
  t->snes               = PETSC_NULL;
  t->funP               = PETSC_NULL;
  t->jacP               = PETSC_NULL;
  t->setupcalled        = 0;
  t->data               = PETSC_NULL;
  t->user               = PETSC_NULL;
  t->max_steps          = 5000;
  t->max_time           = 5.0;
  t->time_step          = .1;
  t->time_step_old      = t->time_step;
  t->initial_time_step  = t->time_step;
  t->steps              = 0;
  t->ptime              = 0.0;
  t->linear_its         = 0;
  t->nonlinear_its      = 0;
  t->work               = PETSC_NULL;
  t->nwork              = 0;
  t->ops->applymatrixbc = TSDefaultSystemMatrixBC;
  t->ops->applyrhsbc    = TSDefaultRhsBC;
  t->ops->applysolbc    = TSDefaultSolutionBC;
  t->ops->prestep       = TSDefaultPreStep;
  t->ops->update        = TSDefaultUpdate;
  t->ops->poststep      = TSDefaultPostStep;
  t->ops->reform        = PETSC_NULL;
  t->ops->reallocate    = PETSC_NULL;
  t->ops->serialize     = PETSC_NULL;

  *ts = t;
  PetscFunctionReturn(0);
}

/* ----- Routines to initialize and destroy a timestepper ---- */

#undef __FUNCT__
#define __FUNCT__ "TSSetUp"
/*@
   TSSetUp - Sets up the internal data structures for the later use
   of a timestepper.

   Collective on TS

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Notes:
   For basic use of the TS solvers the user need not explicitly call
   TSSetUp(), since these actions will automatically occur during
   the call to TSStep().  However, if one wishes to control this
   phase separately, TSSetUp() should be called after TSCreate()
   and optional routines of the form TSSetXXX(), but before TSStep().

   Level: advanced

.keywords: TS, timestep, setup

.seealso: TSCreate(), TSStep(), TSDestroy()
@*/
int TSSetUp(TS ts)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (!ts->vec_sol) SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Must call TSSetSolution() first");
  if (!ts->type_name) {
    ierr = TSSetType(ts,TS_EULER);CHKERRQ(ierr);
  }
  ierr = (*ts->ops->setup)(ts);CHKERRQ(ierr);
  ts->setupcalled = 1;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDestroy"
/*@C
   TSDestroy - Destroys the timestepper context that was created
   with TSCreate().

   Collective on TS

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Level: beginner

.keywords: TS, timestepper, destroy

.seealso: TSCreate(), TSSetUp(), TSSolve()
@*/
int TSDestroy(TS ts)
{
  int ierr,i;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (--ts->refct > 0) PetscFunctionReturn(0);

  /* if memory was published with AMS then destroy it */
  ierr = PetscObjectDepublish(ts);CHKERRQ(ierr);

  if (ts->sles) {ierr = SLESDestroy(ts->sles);CHKERRQ(ierr);}
  if (ts->snes) {ierr = SNESDestroy(ts->snes);CHKERRQ(ierr);}
  ierr = (*(ts)->ops->destroy)(ts);CHKERRQ(ierr);
  for (i=0; i<ts->numbermonitors; i++) {
    if (ts->mdestroy[i]) {
      ierr = (*ts->mdestroy[i])(ts->monitorcontext[i]);CHKERRQ(ierr);
    }
  }
  PetscLogObjectDestroy((PetscObject)ts);
  PetscHeaderDestroy((PetscObject)ts);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetSNES"
/*@C
   TSGetSNES - Returns the SNES (nonlinear solver) associated with
   a TS (timestepper) context. Valid only for nonlinear problems.

   Not Collective, but SNES is parallel if TS is parallel

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  snes - the nonlinear solver context

   Notes:
   The user can then directly manipulate the SNES context to set various
   options, etc.  Likewise, the user can then extract and manipulate the
   SLES, KSP, and PC contexts as well.

   TSGetSNES() does not work for integrators that do not use SNES; in
   this case TSGetSNES() returns PETSC_NULL in snes.

   Level: beginner

.keywords: timestep, get, SNES
@*/
int TSGetSNES(TS ts,SNES *snes)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (ts->problem_type == TS_LINEAR) SETERRQ(PETSC_ERR_ARG_WRONG,"Nonlinear only; use TSGetSLES()");
  *snes = ts->snes;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetSLES"
/*@C
   TSGetSLES - Returns the SLES (linear solver) associated with
   a TS (timestepper) context.

   Not Collective, but SLES is parallel if TS is parallel

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  sles - the nonlinear solver context

   Notes:
   The user can then directly manipulate the SLES context to set various
   options, etc.  Likewise, the user can then extract and manipulate the
   KSP and PC contexts as well.

   TSGetSLES() does not work for integrators that do not use SLES;
   in this case TSGetSLES() returns PETSC_NULL in sles.

   Level: beginner

.keywords: timestep, get, SLES
@*/
int TSGetSLES(TS ts,SLES *sles)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (ts->problem_type != TS_LINEAR) SETERRQ(PETSC_ERR_ARG_WRONG,"Linear only; use TSGetSNES()");
  *sles = ts->sles;
  PetscFunctionReturn(0);
}

/* ----------- Routines to set solver parameters ---------- */

#undef __FUNCT__
#define __FUNCT__ "TSSetDuration"
/*@
   TSSetDuration - Sets the maximum number of timesteps to use and
   maximum time for iteration.

   Collective on TS

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
.  maxsteps - maximum number of iterations to use
-  maxtime - final time to iterate to

   Options Database Keys:
.  -ts_max_steps <maxsteps> - Sets maxsteps
.  -ts_max_time <maxtime> - Sets maxtime

   Notes:
   The default maximum number of iterations is 5000. Default time is 5.0

   Level: intermediate

.keywords: TS, timestep, set, maximum, iterations
@*/
int TSSetDuration(TS ts,int maxsteps,PetscReal maxtime)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->max_steps = maxsteps;
  ts->max_time  = maxtime;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetSolution"
/*@
   TSSetSolution - Sets the initial solution vector
   for use by the TS routines.

   Collective on TS and Vec

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
-  x - the solution vector

   Level: beginner

.keywords: TS, timestep, set, solution, initial conditions
@*/
int TSSetSolution(TS ts,Vec x)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->vec_sol        = ts->vec_sol_always = x;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetRhsBC"
/*@
  TSSetRhsBC - Sets the function which applies boundary conditions
  to the Rhs of each system.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts, Vec rhs, void *ctx);

+ rhs - The current rhs vector
- ctx - The user-context

  Level: intermediate

.keywords: TS, Rhs, boundary conditions
@*/
int TSSetRhsBC(TS ts, int (*func)(TS, Vec, void *))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->applyrhsbc = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultRhsBC"
/*@
  TSDefaultRhsBC - The default boundary condition function which does nothing.

  Collective on TS

  Input Parameters:
+ ts  - The TS context obtained from TSCreate()
. rhs - The Rhs
- ctx - The user-context

  Level: developer

.keywords: TS, Rhs, boundary conditions
@*/
int TSDefaultRhsBC(TS ts,  Vec rhs, void *ctx)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetSystemMatrixBC"
/*@
  TSSetSystemMatrixBC - Sets the function which applies boundary conditions
  to the system matrix and preconditioner of each system.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts, Mat A, Mat B, void *ctx);

+ A   - The current system matrix
. B   - The current preconditioner
- ctx - The user-context

  Level: intermediate

.keywords: TS, System matrix, boundary conditions
@*/
int TSSetSystemMatrixBC(TS ts, int (*func)(TS, Mat, Mat, void *))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->applymatrixbc = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultSystemMatrixBC"
/*@
  TSDefaultSystemMatrixBC - The default boundary condition function which
  does nothing.

  Collective on TS

  Input Parameters:
+ ts  - The TS context obtained from TSCreate()
. A   - The system matrix
. B   - The preconditioner
- ctx - The user-context

  Level: developer

.keywords: TS, System matrix, boundary conditions
@*/
int TSDefaultSystemMatrixBC(TS ts, Mat A, Mat B, void *ctx)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetSolutionBC"
/*@
  TSSetSolutionBC - Sets the function which applies boundary conditions
  to the solution of each system. This is necessary in nonlinear systems
  which time dependent boundary conditions.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts, Vec rsol, void *ctx);

+ sol - The current solution vector
- ctx - The user-context

  Level: intermediate

.keywords: TS, solution, boundary conditions
@*/
int TSSetSolutionBC(TS ts, int (*func)(TS, Vec, void *))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->applysolbc = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultSolutionBC"
/*@
  TSDefaultSolutionBC - The default boundary condition function which
  does nothing.

  Collective on TS

  Input Parameters:
+ ts  - The TS context obtained from TSCreate()
. sol - The solution
- ctx - The user-context

  Level: developer

.keywords: TS, solution, boundary conditions
@*/
int TSDefaultSolutionBC(TS ts, Vec sol, void *ctx)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetPreStep"
/*@
  TSSetPreStep - Sets the general-purpose function
  called once at the beginning of time stepping.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts);

  Level: intermediate

.keywords: TS, timestep
@*/
int TSSetPreStep(TS ts, int (*func)(TS))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->prestep = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultPreStep"
/*@
  TSDefaultPreStep - The default pre-stepping function which does nothing.

  Collective on TS

  Input Parameters:
. ts  - The TS context obtained from TSCreate()

  Level: developer

.keywords: TS, timestep
@*/
int TSDefaultPreStep(TS ts)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetUpdate"
/*@
  TSSetUpdate - Sets the general-purpose update function called
  at the beginning of every time step. This function can change
  the time step.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts, double t, double *dt);

+ t   - The current time
- dt  - The current time step

  Level: intermediate

.keywords: TS, update, timestep
@*/
int TSSetUpdate(TS ts, int (*func)(TS, double, double *))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->update = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultUpdate"
/*@
  TSDefaultUpdate - The default update function which does nothing.

  Collective on TS

  Input Parameters:
+ ts  - The TS context obtained from TSCreate()
- t   - The current time

  Output Parameters:
. dt  - The current time step

  Level: developer

.keywords: TS, update, timestep
@*/
int TSDefaultUpdate(TS ts, double t, double *dt)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSSetPostStep"
/*@
  TSSetPostStep - Sets the general-purpose function
  called once at the end of time stepping.

  Collective on TS

  Input Parameters:
+ ts   - The TS context obtained from TSCreate()
- func - The function

  Calling sequence of func:
. func (TS ts);

  Level: intermediate

.keywords: TS, timestep
@*/
int TSSetPostStep(TS ts, int (*func)(TS))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  ts->ops->poststep = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultPostStep"
/*@
  TSDefaultPostStep - The default post-stepping function which does nothing.

  Collective on TS

  Input Parameters:
. ts  - The TS context obtained from TSCreate()

  Level: developer

.keywords: TS, timestep
@*/
int TSDefaultPostStep(TS ts)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

/* ------------ Routines to set performance monitoring options ----------- */

#undef __FUNCT__
#define __FUNCT__ "TSSetMonitor"
/*@C
   TSSetMonitor - Sets an ADDITIONAL function that is to be used at every
   timestep to display the iteration's  progress.

   Collective on TS

   Input Parameters:
+  ts - the TS context obtained from TSCreate()
.  func - monitoring routine
.  mctx - [optional] user-defined context for private data for the
             monitor routine (use PETSC_NULL if no context is desired)
-  monitordestroy - [optional] routine that frees monitor context
          (may be PETSC_NULL)

   Calling sequence of func:
$    int func(TS ts,int steps,PetscReal time,Vec x,void *mctx)

+    ts - the TS context
.    steps - iteration number
.    time - current time
.    x - current iterate
-    mctx - [optional] monitoring context

   Notes:
   This routine adds an additional monitor to the list of monitors that
   already has been loaded.

   Level: intermediate

.keywords: TS, timestep, set, monitor

.seealso: TSDefaultMonitor(), TSClearMonitor()
@*/
int TSSetMonitor(TS ts,int (*monitor)(TS,int,PetscReal,Vec,void*),void *mctx,int (*mdestroy)(void*))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (ts->numbermonitors >= MAXTSMONITORS) {
    SETERRQ(PETSC_ERR_ARG_OUTOFRANGE,"Too many monitors set");
  }
  ts->monitor[ts->numbermonitors]           = monitor;
  ts->mdestroy[ts->numbermonitors]          = mdestroy;
  ts->monitorcontext[ts->numbermonitors++]  = (void*)mctx;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSClearMonitor"
/*@C
   TSClearMonitor - Clears all the monitors that have been set on a time-step object.

   Collective on TS

   Input Parameters:
.  ts - the TS context obtained from TSCreate()

   Notes:
   There is no way to remove a single, specific monitor.

   Level: intermediate

.keywords: TS, timestep, set, monitor

.seealso: TSDefaultMonitor(), TSSetMonitor()
@*/
int TSClearMonitor(TS ts)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ts->numbermonitors = 0;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSDefaultMonitor"
int TSDefaultMonitor(TS ts,int step,PetscReal ptime,Vec v,void *ctx)
{
  int ierr;

  PetscFunctionBegin;
  ierr = PetscPrintf(ts->comm,"timestep %d dt %g time %g\n",step,ts->time_step,ptime);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSStep"
/*@
   TSStep - Steps the requested number of timesteps.

   Collective on TS

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameters:
+  steps - number of iterations until termination
-  ptime - time until termination

   Level: beginner

.keywords: TS, timestep, solve

.seealso: TSCreate(), TSSetUp(), TSDestroy()
@*/
int TSStep(TS ts,int *steps,PetscReal *ptime)
{
  PetscTruth opt;
  int        ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts, TS_COOKIE);
  if (!ts->setupcalled) {
    ierr = TSSetUp(ts);                                                                                   CHKERRQ(ierr);
  }

  ierr = PetscLogEventBegin(TS_Step, ts, 0, 0, 0);                                                        CHKERRQ(ierr);
  ierr = (*ts->ops->prestep)(ts);                                                                         CHKERRQ(ierr);
  ierr = (*ts->ops->step)(ts, steps, ptime);                                                              CHKERRQ(ierr);
  ierr = (*ts->ops->poststep)(ts);                                                                        CHKERRQ(ierr);
  ierr = PetscLogEventEnd(TS_Step, ts, 0, 0, 0);                                                          CHKERRQ(ierr);

  ierr = PetscOptionsHasName(ts->prefix, "-ts_view", &opt);                                               CHKERRQ(ierr);
  if ((opt == PETSC_TRUE) && !PetscPreLoadingOn) {
    ierr = TSView(ts, PETSC_VIEWER_STDOUT_WORLD);                                                         CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSMonitor"
/*
     Runs the user provided monitor routines, if they exists.
*/
int TSMonitor(TS ts,int step,PetscReal ptime,Vec x)
{
  int i,ierr,n = ts->numbermonitors;

  PetscFunctionBegin;
  for (i=0; i<n; i++) {
    ierr = (*ts->monitor[i])(ts,step,ptime,x,ts->monitorcontext[i]);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

/* ------------------------------------------------------------------------*/

#undef __FUNCT__
#define __FUNCT__ "TSLGMonitorCreate"
/*@C
   TSLGMonitorCreate - Creates a line graph context for use with
   TS to monitor convergence of preconditioned residual norms.

   Collective on TS

   Input Parameters:
+  host - the X display to open, or null for the local machine
.  label - the title to put in the title bar
.  x, y - the screen coordinates of the upper left coordinate of the window
-  m, n - the screen width and height in pixels

   Output Parameter:
.  draw - the drawing context

   Options Database Key:
.  -ts_xmonitor - automatically sets line graph monitor

   Notes:
   Use TSLGMonitorDestroy() to destroy this line graph, not PetscDrawLGDestroy().

   Level: intermediate

.keywords: TS, monitor, line graph, residual, seealso

.seealso: TSLGMonitorDestroy(), TSSetMonitor()

@*/
int TSLGMonitorCreate(char *host,char *label,int x,int y,int m,int n,PetscDrawLG *draw)
{
  PetscDraw win;
  int       ierr;

  PetscFunctionBegin;
  ierr = PetscDrawCreate(PETSC_COMM_SELF,host,label,x,y,m,n,&win);CHKERRQ(ierr);
  ierr = PetscDrawSetType(win,PETSC_DRAW_X);CHKERRQ(ierr);
  ierr = PetscDrawLGCreate(win,1,draw);CHKERRQ(ierr);
  ierr = PetscDrawLGIndicateDataPoints(*draw);CHKERRQ(ierr);

  PetscLogObjectParent(*draw,win);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSLGMonitor"
int TSLGMonitor(TS ts,int n,PetscReal ptime,Vec v,void *monctx)
{
  PetscDrawLG lg = (PetscDrawLG) monctx;
  PetscReal      x,y = ptime;
  int         ierr;

  PetscFunctionBegin;
  if (!monctx) {
    MPI_Comm    comm;
    PetscViewer viewer;

    ierr   = PetscObjectGetComm((PetscObject)ts,&comm);CHKERRQ(ierr);
    viewer = PETSC_VIEWER_DRAW_(comm);
    ierr   = PetscViewerDrawGetDrawLG(viewer,0,&lg);CHKERRQ(ierr);
  }

  if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
  x = (PetscReal)n;
  ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
  if (n < 20 || (n % 5)) {
    ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSLGMonitorDestroy"
/*@C
   TSLGMonitorDestroy - Destroys a line graph context that was created
   with TSLGMonitorCreate().

   Collective on PetscDrawLG

   Input Parameter:
.  draw - the drawing context

   Level: intermediate

.keywords: TS, monitor, line graph, destroy

.seealso: TSLGMonitorCreate(),  TSSetMonitor(), TSLGMonitor();
@*/
int TSLGMonitorDestroy(PetscDrawLG drawlg)
{
  PetscDraw draw;
  int       ierr;

  PetscFunctionBegin;
  ierr = PetscDrawLGGetDraw(drawlg,&draw);CHKERRQ(ierr);
  ierr = PetscDrawDestroy(draw);CHKERRQ(ierr);
  ierr = PetscDrawLGDestroy(drawlg);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetTime"
/*@
   TSGetTime - Gets the current time.

   Not Collective

   Input Parameter:
.  ts - the TS context obtained from TSCreate()

   Output Parameter:
.  t  - the current time

   Contributed by: Matthew Knepley

   Level: beginner

.seealso: TSSetInitialTimeStep(), TSGetTimeStep()

.keywords: TS, get, time
@*/
int TSGetTime(TS ts,PetscReal* t)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *t = ts->ptime;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetProblemType"
/*@C
   TSGetProblemType - Returns the problem type of a TS (timestepper) context.

   Not Collective

   Input Parameter:
.  ts   - The TS context obtained from TSCreate()

   Output Parameter:
.  type - The problem type, TS_LINEAR or TS_NONLINEAR

   Level: intermediate

   Contributed by: Matthew Knepley

.keywords: ts, get, type

@*/
int TSGetProblemType(TS ts,TSProblemType *type)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  *type = ts->problem_type;
  PetscFunctionReturn(0);
}

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

   Collective on TS

   Input Parameter:
+  ts     - The TS 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.

   Contributed by: Matthew Knepley

   Level: advanced

.keywords: TS, set, options, prefix, database

.seealso: TSSetFromOptions()

@*/
int TSSetOptionsPrefix(TS ts,char *prefix)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ierr = PetscObjectSetOptionsPrefix((PetscObject)ts,prefix);CHKERRQ(ierr);
  switch(ts->problem_type) {
    case TS_NONLINEAR:
      ierr = SNESSetOptionsPrefix(ts->snes,prefix);CHKERRQ(ierr);
      break;
    case TS_LINEAR:
      ierr = SLESSetOptionsPrefix(ts->sles,prefix);CHKERRQ(ierr);
      break;
  }
  PetscFunctionReturn(0);
}


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

   Collective on TS

   Input Parameter:
+  ts     - The TS 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.

   Contributed by: Matthew Knepley

   Level: advanced

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

.seealso: TSGetOptionsPrefix()

@*/
int TSAppendOptionsPrefix(TS ts,char *prefix)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ierr = PetscObjectAppendOptionsPrefix((PetscObject)ts,prefix);CHKERRQ(ierr);
  switch(ts->problem_type) {
    case TS_NONLINEAR:
      ierr = SNESAppendOptionsPrefix(ts->snes,prefix);CHKERRQ(ierr);
      break;
    case TS_LINEAR:
      ierr = SLESAppendOptionsPrefix(ts->sles,prefix);CHKERRQ(ierr);
      break;
  }
  PetscFunctionReturn(0);
}

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

   Not Collective

   Input Parameter:
.  ts - The TS context

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

   Contributed by: Matthew Knepley

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

   Level: intermediate

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

.seealso: TSAppendOptionsPrefix()
@*/
int TSGetOptionsPrefix(TS ts,char **prefix)
{
  int ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  ierr = PetscObjectGetOptionsPrefix((PetscObject)ts,prefix);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetRHSMatrix"
/*@C
   TSGetRHSMatrix - Returns the matrix A at the present timestep.

   Not Collective, but parallel objects are returned if TS is parallel

   Input Parameter:
.  ts  - The TS context obtained from TSCreate()

   Output Parameters:
+  A   - The matrix A, where U_t = A(t) U
.  M   - The preconditioner matrix, usually the same as A
-  ctx - User-defined context for matrix evaluation routine

   Notes: You can pass in PETSC_NULL for any return argument you do not need.

   Contributed by: Matthew Knepley

   Level: intermediate

.seealso: TSGetTimeStep(), TSGetTime(), TSGetTimeStepNumber(), TSGetRHSJacobian()

.keywords: TS, timestep, get, matrix

@*/
int TSGetRHSMatrix(TS ts,Mat *A,Mat *M,void **ctx)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_COOKIE);
  if (A)   *A = ts->A;
  if (M)   *M = ts->B;
  if (ctx) *ctx = ts->jacP;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "TSGetRHSJacobian"
/*@C
   TSGetRHSJacobian - Returns the Jacobian J at the present timestep.

   Not Collective, but parallel objects are returned if TS is parallel

   Input Parameter:
.  ts  - The TS context obtained from TSCreate()

   Output Parameters:
+  J   - The Jacobian J of F, where U_t = F(U,t)
.  M   - The preconditioner matrix, usually the same as J
- ctx - User-defined context for Jacobian evaluation routine

   Notes: You can pass in PETSC_NULL for any return argument you do not need.

   Contributed by: Matthew Knepley

   Level: intermediate

.seealso: TSGetTimeStep(), TSGetRHSMatrix(), TSGetTime(), TSGetTimeStepNumber()

.keywords: TS, timestep, get, matrix, Jacobian
@*/
int TSGetRHSJacobian(TS ts,Mat *J,Mat *M,void **ctx)
{
  int ierr;

  PetscFunctionBegin;
  ierr = TSGetRHSMatrix(ts,J,M,ctx);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*MC
   TSRegisterDynamic - Adds a method to the timestepping solver package.

   Synopsis:
   int TSRegisterDynamic(char *name_solver,char *path,char *name_create,int (*routine_create)(TS))

   Not collective

   Input Parameters:
+  name_solver - name of a new user-defined solver
.  path - path (either absolute or relative) the library containing this solver
.  name_create - name of routine to create method context
-  routine_create - routine to create method context

   Notes:
   TSRegisterDynamic() may be called multiple times to add several user-defined solvers.

   If dynamic libraries are used, then the fourth input argument (routine_create)
   is ignored.

   Sample usage:
.vb
   TSRegisterDynamic("my_solver",/home/username/my_lib/lib/libO/solaris/mylib.a,
              "MySolverCreate",MySolverCreate);
.ve

   Then, your solver can be chosen with the procedural interface via
$     TSSetType(ts,"my_solver")
   or at runtime via the option
$     -ts_type my_solver

   Level: advanced

   Environmental variables such as ${PETSC_ARCH}, ${PETSC_DIR}, ${PETSC_LIB_DIR}, ${BOPT},
   and others of the form ${any_environmental_variable} occuring in pathname will be
   replaced with appropriate values.

.keywords: TS, register

.seealso: TSRegisterAll(), TSRegisterDestroy()
M*/

#undef __FUNCT__
#define __FUNCT__ "TSRegister"
int TSRegister(const char sname[], const char path[], const char name[], int (*function)(TS))
{
  char fullname[256];
  int  ierr;

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

#undef __FUNCT__
#define __FUNCT__ "TSVecViewMonitor"
/*@C
   TSVecViewMonitor - Monitors progress of the TS solvers by calling
   VecView() for the solution at each timestep

   Collective on TS

   Input Parameters:
+  ts - the TS context
.  step - current time-step
.  ptime - current time
-  dummy - either a viewer or PETSC_NULL

   Level: intermediate

.keywords: TS,  vector, monitor, view

.seealso: TSSetMonitor(), TSDefaultMonitor(), VecView()
@*/
int TSVecViewMonitor(TS ts,int step,PetscReal ptime,Vec x,void *dummy)
{
  int         ierr;
  PetscViewer viewer = (PetscViewer) dummy;

  PetscFunctionBegin;
  if (!viewer) {
    MPI_Comm comm;
    ierr   = PetscObjectGetComm((PetscObject)ts,&comm);CHKERRQ(ierr);
    viewer = PETSC_VIEWER_DRAW_(comm);
  }
  ierr = VecView(x,viewer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}