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: }