Date: 2013-07-02T14:49:23+00:00

Actual source code: snesmfj.c
petsc-3.4.2 2013-07-02

      2: #include <petsc-private/snesimpl.h>  /*I  "petscsnes.h" I*/
      3: #include <petscdm.h>                 /*I  "petscdm.h"   I*/
      4: #include <../src/mat/impls/mffd/mffdimpl.h>
      5: #include <petsc-private/matimpl.h>

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

     14:    Logically Collective on SNES

     16:    Input Parameters:
     17: +   snes - the nonlinear solver context
     18: .   x - the point at which the Jacobian vector products will be performed
     19: .   jac - the matrix-free Jacobian object
     20: .   B - either the same as jac or another matrix type (ignored)
     21: .   flag - not relevent for matrix-free form
     22: -   dummy - the user context (ignored)

     24:    Level: developer

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

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

     38: .seealso: MatMFFDGetH(), MatCreateSNESMF(), MatCreateMFFD(), MATMFFD,
     39:           MatMFFDSetHHistory(), MatMFFDSetFunctionError(), MatCreateMFFD(), SNESSetJacobian()

     41: @*/
     42: PetscErrorCode  MatMFFDComputeJacobian(SNES snes,Vec x,Mat *jac,Mat *B,MatStructure *flag,void *dummy)
     43: {

     47:   MatAssemblyBegin(*jac,MAT_FINAL_ASSEMBLY);
     48:   MatAssemblyEnd(*jac,MAT_FINAL_ASSEMBLY);
     49:   return(0);
     50: }

     52: PETSC_EXTERN PetscErrorCode MatAssemblyEnd_MFFD(Mat,MatAssemblyType);
     53: PETSC_EXTERN PetscErrorCode MatMFFDSetBase_MFFD(Mat,Vec,Vec);

     57: /*
     58:    MatAssemblyEnd_SNESMF - Calls MatAssemblyEnd_MFFD() and then sets the
     59:     base from the SNES context

     61: */
     62: PetscErrorCode MatAssemblyEnd_SNESMF(Mat J,MatAssemblyType mt)
     63: {
     65:   MatMFFD        j    = (MatMFFD)J->data;
     66:   SNES           snes = (SNES)j->funcctx;
     67:   Vec            u,f;

     70:   MatAssemblyEnd_MFFD(J,mt);

     72:   SNESGetSolution(snes,&u);
     73:   SNESGetFunction(snes,&f,NULL,NULL);
     74:   MatMFFDSetBase_MFFD(J,u,f);
     75:   return(0);
     76: }

     78: /*
     79:     This routine resets the MatAssemblyEnd() for the MatMFFD created from MatCreateSNESMF() so that it NO longer
     80:   uses the solution in the SNES object to update the base. See the warning in MatCreateSNESMF().
     81: */
     84: PetscErrorCode  MatMFFDSetBase_SNESMF(Mat J,Vec U,Vec F)
     85: {

     89:   MatMFFDSetBase_MFFD(J,U,F);

     91:   J->ops->assemblyend = MatAssemblyEnd_MFFD;
     92:   return(0);
     93: }

     97: /*@
     98:    MatCreateSNESMF - Creates a matrix-free matrix context for use with
     99:    a SNES solver.  This matrix can be used as the Jacobian argument for
    100:    the routine SNESSetJacobian(). See MatCreateMFFD() for details on how
    101:    the finite difference computation is done.

    103:    Collective on SNES and Vec

    105:    Input Parameters:
    106: .  snes - the SNES context

    108:    Output Parameter:
    109: .  J - the matrix-free matrix

    111:    Level: advanced

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

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

    122: .seealso: MatDestroy(), MatMFFDSetFunctionError(), MatMFFDDSSetUmin()
    123:           MatMFFDSetHHistory(), MatMFFDResetHHistory(), MatCreateMFFD(),
    124:           MatMFFDGetH(), MatMFFDRegister(), MatMFFDComputeJacobian()

    126: @*/
    127: PetscErrorCode  MatCreateSNESMF(SNES snes,Mat *J)
    128: {
    130:   PetscInt       n,N;

    133:   if (snes->vec_func) {
    134:     VecGetLocalSize(snes->vec_func,&n);
    135:     VecGetSize(snes->vec_func,&N);
    136:   } else if (snes->dm) {
    137:     Vec tmp;
    138:     DMGetGlobalVector(snes->dm,&tmp);
    139:     VecGetLocalSize(tmp,&n);
    140:     VecGetSize(tmp,&N);
    141:     DMRestoreGlobalVector(snes->dm,&tmp);
    142:   } else SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Must call SNESSetFunction() or SNESSetDM() first");
    143:   MatCreateMFFD(PetscObjectComm((PetscObject)snes),n,n,N,N,J);
    144:   MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction,snes);

    146:   (*J)->ops->assemblyend = MatAssemblyEnd_SNESMF;

    148:   PetscObjectComposeFunction((PetscObject)*J,"MatMFFDSetBase_C",MatMFFDSetBase_SNESMF);
    149:   return(0);
    150: }