snes/mf/snesmfj.c

#include <petsc/private/snesimpl.h> /*I  "petscsnes.h" I*/
#include <petscdm.h>                /*I  "petscdm.h"   I*/
#include <../src/mat/impls/mffd/mffdimpl.h>
#include <petsc/private/matimpl.h>

/*@C
   MatMFFDComputeJacobian - Tells the matrix-free Jacobian object the new location at which
       Jacobian matrix vector products will be computed at, i.e. J(x) * a. The x is obtained
       from the `SNES` object (using `SNESGetSolution()`).

   Collective

   Input Parameters:
+   snes - the nonlinear solver context
.   x - the point at which the Jacobian vector products will be performed
.   jac - the matrix-free Jacobian object of `MatType` `MATMFFD`, likely obtained with `MatCreateSNESMF()`
.   B - either the same as jac or another matrix type (ignored)
.   flag - not relevant for matrix-free form
-   dummy - the user context (ignored)

   Options Database Key:
.  -snes_mf - use the matrix created with `MatSNESMFCreate()` to setup the Jacobian for each new solution in the Newton process

   Level: developer

   Notes:
      If `MatMFFDSetBase()` is ever called on jac then this routine will NO longer get
    the x from the `SNES` object and `MatMFFDSetBase()` must from that point on be used to
    change the base vector x.

     This can be passed into `SNESSetJacobian()` as the Jacobian evaluation function argument
     when using a completely matrix-free solver,
     that is the B matrix is also the same matrix operator. This is used when you select
     -snes_mf but rarely used directly by users. (All this routine does is call `MatAssemblyBegin/End()` on
     the `Mat` jac.)

.seealso: `MatMFFDGetH()`, `MatCreateSNESMF()`, `MatMFFDSetBase()`, `MatCreateMFFD()`, `MATMFFD`,
          `MatMFFDSetHHistory()`, `MatMFFDSetFunctionError()`, `MatCreateMFFD()`, `SNESSetJacobian()`
@*/
PetscErrorCode MatMFFDComputeJacobian(SNES snes, Vec x, Mat jac, Mat B, void *dummy)
{
  PetscFunctionBegin;
  PetscCall(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_EXTERN PetscErrorCode MatAssemblyEnd_MFFD(Mat, MatAssemblyType);
PETSC_EXTERN PetscErrorCode MatMFFDSetBase_MFFD(Mat, Vec, Vec);

/*@
    MatSNESMFGetSNES - returns the `SNES` associated with a matrix created with `MatCreateSNESMF()`

    Not Collective

    Input Parameter:
.   J - the matrix

    Output Parameter:
.   snes - the `SNES` object

    Level: advanced

.seealso: `Mat`, `SNES`, `MatCreateSNESMF()`
@*/
PetscErrorCode MatSNESMFGetSNES(Mat J, SNES *snes)
{
  MatMFFD j;

  PetscFunctionBegin;
  PetscCall(MatShellGetContext(J, &j));
  *snes = (SNES)j->ctx;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
   MatAssemblyEnd_SNESMF - Calls MatAssemblyEnd_MFFD() and then sets the
    base from the SNES context

*/
static PetscErrorCode MatAssemblyEnd_SNESMF(Mat J, MatAssemblyType mt)
{
  MatMFFD j;
  SNES    snes;
  Vec     u, f;
  DM      dm;
  DMSNES  dms;

  PetscFunctionBegin;
  PetscCall(MatShellGetContext(J, &j));
  snes = (SNES)j->ctx;
  PetscCall(MatAssemblyEnd_MFFD(J, mt));

  PetscCall(SNESGetSolution(snes, &u));
  PetscCall(SNESGetDM(snes, &dm));
  PetscCall(DMGetDMSNES(dm, &dms));
  if ((j->func == (PetscErrorCode(*)(void *, Vec, Vec))SNESComputeFunction) && !dms->ops->computemffunction) {
    PetscCall(SNESGetFunction(snes, &f, NULL, NULL));
    PetscCall(MatMFFDSetBase_MFFD(J, u, f));
  } else {
    /* f value known by SNES is not correct for other differencing function */
    PetscCall(MatMFFDSetBase_MFFD(J, u, NULL));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
   MatAssemblyEnd_SNESMF_UseBase - Calls MatAssemblyEnd_MFFD() and then sets the
    base from the SNES context. This version will cause the base to be used for differencing
    even if the func is not SNESComputeFunction. See: MatSNESMFUseBase()

*/
static PetscErrorCode MatAssemblyEnd_SNESMF_UseBase(Mat J, MatAssemblyType mt)
{
  MatMFFD j;
  SNES    snes;
  Vec     u, f;

  PetscFunctionBegin;
  PetscCall(MatAssemblyEnd_MFFD(J, mt));
  PetscCall(MatShellGetContext(J, &j));
  snes = (SNES)j->ctx;
  PetscCall(SNESGetSolution(snes, &u));
  PetscCall(SNESGetFunction(snes, &f, NULL, NULL));
  PetscCall(MatMFFDSetBase_MFFD(J, u, f));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
    This routine resets the MatAssemblyEnd() for the MatMFFD created from MatCreateSNESMF() so that it NO longer
  uses the solution in the SNES object to update the base. See the warning in MatCreateSNESMF().
*/
static PetscErrorCode MatMFFDSetBase_SNESMF(Mat J, Vec U, Vec F)
{
  PetscFunctionBegin;
  PetscCall(MatMFFDSetBase_MFFD(J, U, F));
  J->ops->assemblyend = MatAssemblyEnd_MFFD;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSNESMFSetReuseBase_SNESMF(Mat J, PetscBool use)
{
  PetscFunctionBegin;
  if (use) {
    J->ops->assemblyend = MatAssemblyEnd_SNESMF_UseBase;
  } else {
    J->ops->assemblyend = MatAssemblyEnd_SNESMF;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
    MatSNESMFSetReuseBase - Causes the base vector to be used for differencing even if the function provided to `SNESSetFunction()` is not the
                       same as that provided to `MatMFFDSetFunction()`.

    Logically Collective

    Input Parameters:
+   J - the `MATMFFD` matrix
-   use - if true always reuse the base vector instead of recomputing f(u) even if the function in the `MATMFFD` is
          not `SNESComputeFunction()`

    Level: advanced

    Note:
    Care must be taken when using this routine to insure that the function provided to `MatMFFDSetFunction()`, call it F_MF() is compatible with
    with that provided to `SNESSetFunction()`, call it F_SNES(). That is, (F_MF(u + h*d) - F_SNES(u))/h has to approximate the derivative

    Developer Note:
    This was provided for the MOOSE team who desired to have a `SNESSetFunction()` function that could change configurations (similar to variable
    switching) to contacts while the function provided to `MatMFFDSetFunction()` cannot. Except for the possibility of changing the configuration
    both functions compute the same mathematical function so the differencing makes sense.

.seealso: `MATMFFD`, `MatMFFDSetFunction()`, `SNESSetFunction()`, `MatCreateSNESMF()`, `MatSNESMFGetReuseBase()`
@*/
PetscErrorCode MatSNESMFSetReuseBase(Mat J, PetscBool use)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(J, MAT_CLASSID, 1);
  PetscTryMethod(J, "MatSNESMFSetReuseBase_C", (Mat, PetscBool), (J, use));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSNESMFGetReuseBase_SNESMF(Mat J, PetscBool *use)
{
  PetscFunctionBegin;
  if (J->ops->assemblyend == MatAssemblyEnd_SNESMF_UseBase) *use = PETSC_TRUE;
  else *use = PETSC_FALSE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
    MatSNESMFGetReuseBase - Determines if the base vector is to be used for differencing even if the function provided to `SNESSetFunction()` is not the
                       same as that provided to `MatMFFDSetFunction()`.

    Logically Collective

    Input Parameter:
.   J - the `MATMFFD` matrix

    Output Parameter:
.   use - if true always reuse the base vector instead of recomputing f(u) even if the function in the `MATMFFD` is
          not `SNESComputeFunction()`

    Level: advanced

    Note:
    See `MatSNESMFSetReuseBase()`

.seealso: `MatSNESMFSetReuseBase()`, `MatCreateSNESMF()`, `MatSNESMFSetReuseBase()`
@*/
PetscErrorCode MatSNESMFGetReuseBase(Mat J, PetscBool *use)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(J, MAT_CLASSID, 1);
  PetscUseMethod(J, "MatSNESMFGetReuseBase_C", (Mat, PetscBool *), (J, use));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
   MatCreateSNESMF - Creates a matrix-free matrix context for use with
   a `SNES` solver.  This matrix can be used as the Jacobian argument for
   the routine `SNESSetJacobian()`. See `MatCreateMFFD()` for details on how
   the finite difference computation is done.

   Collective

   Input Parameters:
.  snes - the `SNES` context

   Output Parameter:
.  J - the matrix-free matrix which is of type `MATMFFD`

   Level: advanced

   Notes:
     You can call `SNESSetJacobian()` with `MatMFFDComputeJacobian()` if you are using matrix and not a different
     preconditioner matrix

     If you wish to provide a different function to do differencing on to compute the matrix-free operator than
     that provided to `SNESSetFunction()` then call `MatMFFDSetFunction()` with your function after this call.

     The difference between this routine and `MatCreateMFFD()` is that this matrix
     automatically gets the current base vector from the `SNES` object and not from an
     explicit call to `MatMFFDSetBase()`.

     If `MatMFFDSetBase()` is ever called on jac then this routine will NO longer get
     the x from the `SNES` object and `MatMFFDSetBase()` must from that point on be used to
     change the base vector x.

     Using a different function for the differencing will not work if you are using non-linear left preconditioning.

.seealso: `MATMFFD, `MatDestroy()`, `MatMFFDSetFunction()`, `MatMFFDSetFunctionError()`, `MatMFFDDSSetUmin()`
          `MatMFFDSetHHistory()`, `MatMFFDResetHHistory()`, `MatCreateMFFD()`,
          `MatMFFDGetH()`, `MatMFFDRegister()`, `MatMFFDComputeJacobian()`, `MatSNESMFSetReuseBase()`, `MatSNESMFGetReuseBase()`
@*/
PetscErrorCode MatCreateSNESMF(SNES snes, Mat *J)
{
  PetscInt n, N;
  MatMFFD  mf;

  PetscFunctionBegin;
  if (snes->vec_func) {
    PetscCall(VecGetLocalSize(snes->vec_func, &n));
    PetscCall(VecGetSize(snes->vec_func, &N));
  } else if (snes->dm) {
    Vec tmp;
    PetscCall(DMGetGlobalVector(snes->dm, &tmp));
    PetscCall(VecGetLocalSize(tmp, &n));
    PetscCall(VecGetSize(tmp, &N));
    PetscCall(DMRestoreGlobalVector(snes->dm, &tmp));
  } else SETERRQ(PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() first");
  PetscCall(MatCreateMFFD(PetscObjectComm((PetscObject)snes), n, n, N, N, J));
  PetscCall(MatShellGetContext(*J, &mf));
  mf->ctx = snes;

  if (snes->npc && snes->npcside == PC_LEFT) {
    PetscCall(MatMFFDSetFunction(*J, (PetscErrorCode(*)(void *, Vec, Vec))SNESComputeFunctionDefaultNPC, snes));
  } else {
    DM     dm;
    DMSNES dms;

    PetscCall(SNESGetDM(snes, &dm));
    PetscCall(DMGetDMSNES(dm, &dms));
    PetscCall(MatMFFDSetFunction(*J, (PetscErrorCode(*)(void *, Vec, Vec))(dms->ops->computemffunction ? SNESComputeMFFunction : SNESComputeFunction), snes));
  }
  (*J)->ops->assemblyend = MatAssemblyEnd_SNESMF;

  PetscCall(PetscObjectComposeFunction((PetscObject)*J, "MatMFFDSetBase_C", MatMFFDSetBase_SNESMF));
  PetscCall(PetscObjectComposeFunction((PetscObject)*J, "MatSNESMFSetReuseBase_C", MatSNESMFSetReuseBase_SNESMF));
  PetscCall(PetscObjectComposeFunction((PetscObject)*J, "MatSNESMFGetReuseBase_C", MatSNESMFGetReuseBase_SNESMF));
  PetscFunctionReturn(PETSC_SUCCESS);
}