Actual source code: snesmfj.c

petsc-dev 2014-08-27
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  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,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->ctx;
 67:   Vec            u,f;

 70:   MatAssemblyEnd_MFFD(J,mt);

 72:   SNESGetSolution(snes,&u);
 73:   if (j->func == (PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction) {
 74:     SNESGetFunction(snes,&f,NULL,NULL);
 75:     MatMFFDSetBase_MFFD(J,u,f);
 76:   } else {
 77:     /* f value known by SNES is not correct for other differencing function */
 78:     MatMFFDSetBase_MFFD(J,u,NULL);
 79:   }
 80:   return(0);
 81: }

 83: /*
 84:     This routine resets the MatAssemblyEnd() for the MatMFFD created from MatCreateSNESMF() so that it NO longer
 85:   uses the solution in the SNES object to update the base. See the warning in MatCreateSNESMF().
 86: */
 89: PetscErrorCode  MatMFFDSetBase_SNESMF(Mat J,Vec U,Vec F)
 90: {

 94:   MatMFFDSetBase_MFFD(J,U,F);

 96:   J->ops->assemblyend = MatAssemblyEnd_MFFD;
 97:   return(0);
 98: }

102: /*@
103:    MatCreateSNESMF - Creates a matrix-free matrix context for use with
104:    a SNES solver.  This matrix can be used as the Jacobian argument for
105:    the routine SNESSetJacobian(). See MatCreateMFFD() for details on how
106:    the finite difference computation is done.

108:    Collective on SNES and Vec

110:    Input Parameters:
111: .  snes - the SNES context

113:    Output Parameter:
114: .  J - the matrix-free matrix

116:    Level: advanced


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

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

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

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

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


139: .seealso: MatDestroy(), MatMFFDSetFunction(), MatMFFDSetFunctionError(), MatMFFDDSSetUmin()
140:           MatMFFDSetHHistory(), MatMFFDResetHHistory(), MatCreateMFFD(),
141:           MatMFFDGetH(), MatMFFDRegister(), MatMFFDComputeJacobian()

143: @*/
144: PetscErrorCode  MatCreateSNESMF(SNES snes,Mat *J)
145: {
147:   PetscInt       n,N;
148:   MatMFFD        mf;

151:   if (snes->vec_func) {
152:     VecGetLocalSize(snes->vec_func,&n);
153:     VecGetSize(snes->vec_func,&N);
154:   } else if (snes->dm) {
155:     Vec tmp;
156:     DMGetGlobalVector(snes->dm,&tmp);
157:     VecGetLocalSize(tmp,&n);
158:     VecGetSize(tmp,&N);
159:     DMRestoreGlobalVector(snes->dm,&tmp);
160:   } else SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Must call SNESSetFunction() or SNESSetDM() first");
161:   MatCreateMFFD(PetscObjectComm((PetscObject)snes),n,n,N,N,J);
162:   mf      = (MatMFFD)(*J)->data;
163:   mf->ctx = snes;

165:   if (snes->pc && snes->pcside == PC_LEFT) {
166:     MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunctionDefaultNPC,snes);
167:   } else {
168:     MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction,snes);
169:   }

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

173:   PetscObjectComposeFunction((PetscObject)*J,"MatMFFDSetBase_C",MatMFFDSetBase_SNESMF);
174:   return(0);
175: }