Actual source code: snesmfj.c

petsc-3.14.6 2021-03-30
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  2: #include <petsc/private/snesimpl.h>
  3: #include <petscdm.h>
  4: #include <../src/mat/impls/mffd/mffdimpl.h>
  5: #include <petsc/private/matimpl.h>

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

 12:    Logically Collective on SNES

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

 22:    Level: developer

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

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

 36: .seealso: MatMFFDGetH(), MatCreateSNESMF(), MatCreateMFFD(), MATMFFD,
 37:           MatMFFDSetHHistory(), MatMFFDSetFunctionError(), MatCreateMFFD(), SNESSetJacobian()

 39: @*/
 40: PetscErrorCode  MatMFFDComputeJacobian(SNES snes,Vec x,Mat jac,Mat B,void *dummy)
 41: {

 45:   MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);
 46:   MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);
 47:   return(0);
 48: }

 50: PETSC_EXTERN PetscErrorCode MatAssemblyEnd_MFFD(Mat,MatAssemblyType);
 51: PETSC_EXTERN PetscErrorCode MatMFFDSetBase_MFFD(Mat,Vec,Vec);

 53: /*@
 54:     MatSNESMFGetSNES - returns the SNES associated with a matrix created with MatCreateSNESMF()

 56:     Not collective

 58:     Input Parameter:
 59: .   J - the matrix

 61:     Output Parameter:
 62: .   snes - the SNES object

 64:     Level: advanced

 66: .seealso: MatCreateSNESMF()
 67: @*/
 68: PetscErrorCode MatSNESMFGetSNES(Mat J,SNES *snes)
 69: {
 70:   MatMFFD        j;

 74:   MatShellGetContext(J,&j);
 75:   *snes = (SNES)j->ctx;
 76:   return(0);
 77: }

 79: /*
 80:    MatAssemblyEnd_SNESMF - Calls MatAssemblyEnd_MFFD() and then sets the
 81:     base from the SNES context

 83: */
 84: static PetscErrorCode MatAssemblyEnd_SNESMF(Mat J,MatAssemblyType mt)
 85: {
 87:   MatMFFD        j;
 88:   SNES           snes;
 89:   Vec            u,f;

 92:   MatShellGetContext(J,&j);
 93:   snes = (SNES)j->ctx;
 94:   MatAssemblyEnd_MFFD(J,mt);

 96:   SNESGetSolution(snes,&u);
 97:   if (j->func == (PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction) {
 98:     SNESGetFunction(snes,&f,NULL,NULL);
 99:     MatMFFDSetBase_MFFD(J,u,f);
100:   } else {
101:     /* f value known by SNES is not correct for other differencing function */
102:     MatMFFDSetBase_MFFD(J,u,NULL);
103:   }
104:   return(0);
105: }

107: /*
108:    MatAssemblyEnd_SNESMF_UseBase - Calls MatAssemblyEnd_MFFD() and then sets the
109:     base from the SNES context. This version will cause the base to be used for differencing
110:     even if the func is not SNESComputeFunction. See: MatSNESMFUseBase()


113: */
114: static PetscErrorCode MatAssemblyEnd_SNESMF_UseBase(Mat J,MatAssemblyType mt)
115: {
117:   MatMFFD        j;
118:   SNES           snes;
119:   Vec            u,f;

122:   MatAssemblyEnd_MFFD(J,mt);
123:   MatShellGetContext(J,&j);
124:   snes = (SNES)j->ctx;
125:   SNESGetSolution(snes,&u);
126:   SNESGetFunction(snes,&f,NULL,NULL);
127:   MatMFFDSetBase_MFFD(J,u,f);
128:   return(0);
129: }

131: /*
132:     This routine resets the MatAssemblyEnd() for the MatMFFD created from MatCreateSNESMF() so that it NO longer
133:   uses the solution in the SNES object to update the base. See the warning in MatCreateSNESMF().
134: */
135: static PetscErrorCode  MatMFFDSetBase_SNESMF(Mat J,Vec U,Vec F)
136: {

140:   MatMFFDSetBase_MFFD(J,U,F);
141:   J->ops->assemblyend = MatAssemblyEnd_MFFD;
142:   return(0);
143: }

145: static PetscErrorCode  MatSNESMFSetReuseBase_SNESMF(Mat J,PetscBool use)
146: {
148:   if (use) {
149:     J->ops->assemblyend = MatAssemblyEnd_SNESMF_UseBase;
150:   } else {
151:     J->ops->assemblyend = MatAssemblyEnd_SNESMF;
152:   }
153:   return(0);
154: }

156: /*@
157:     MatSNESMFSetReuseBase - Causes the base vector to be used for differencing even if the function provided to SNESSetFunction() is not the
158:                        same as that provided to MatMFFDSetFunction().

160:     Logically Collective on Mat

162:     Input Parameters:
163: +   J - the MatMFFD matrix
164: -   use - if true always reuse the base vector instead of recomputing f(u) even if the function in the MatSNESMF is
165:           not SNESComputeFunction()

167:     Notes:
168:     Care must be taken when using this routine to insure that the function provided to MatMFFDSetFunction(), call it F_MF() is compatible with
169:            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

171:     Developer Notes:
172:     This was provided for the MOOSE team who desired to have a SNESSetFunction() function that could change configurations due
173:                      to contacts while the function provided to MatMFFDSetFunction() cannot. Except for the possibility of changing the configuration
174:                      both functions compute the same mathematical function so the differencing makes sense.

176:     Level: advanced

178: .seealso: MatCreateSNESMF(), MatSNESMFGetReuseBase()
179: @*/
180: PetscErrorCode  MatSNESMFSetReuseBase(Mat J,PetscBool use)
181: {

186:   PetscTryMethod(J,"MatSNESMFSetReuseBase_C",(Mat,PetscBool),(J,use));
187:   return(0);
188: }

190: static PetscErrorCode  MatSNESMFGetReuseBase_SNESMF(Mat J,PetscBool *use)
191: {
193:   if (J->ops->assemblyend == MatAssemblyEnd_SNESMF_UseBase) *use = PETSC_TRUE;
194:   else *use = PETSC_FALSE;
195:   return(0);
196: }

198: /*@
199:     MatSNESMFGetReuseBase - Determines if the base vector is to be used for differencing even if the function provided to SNESSetFunction() is not the
200:                        same as that provided to MatMFFDSetFunction().

202:     Logically Collective on Mat

204:     Input Parameter:
205: .   J - the MatMFFD matrix

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

211:     Notes:
212:     Care must be taken when using this routine to insure that the function provided to MatMFFDSetFunction(), call it F_MF() is compatible with
213:            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

215:     Developer Notes:
216:     This was provided for the MOOSE team who desired to have a SNESSetFunction() function that could change configurations due
217:                      to contacts while the function provided to MatMFFDSetFunction() cannot. Except for the possibility of changing the configuration
218:                      both functions compute the same mathematical function so the differencing makes sense.

220:     Level: advanced

222: .seealso: MatCreateSNESMF(), MatSNESMFSetReuseBase()
223: @*/
224: PetscErrorCode  MatSNESMFGetReuseBase(Mat J,PetscBool *use)
225: {

230:   PetscUseMethod(J,"MatSNESMFGetReuseBase_C",(Mat,PetscBool*),(J,use));
231:   return(0);
232: }

234: /*@
235:    MatCreateSNESMF - Creates a matrix-free matrix context for use with
236:    a SNES solver.  This matrix can be used as the Jacobian argument for
237:    the routine SNESSetJacobian(). See MatCreateMFFD() for details on how
238:    the finite difference computation is done.

240:    Collective on SNES

242:    Input Parameters:
243: .  snes - the SNES context

245:    Output Parameter:
246: .  J - the matrix-free matrix

248:    Level: advanced


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

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

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

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

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


271: .seealso: MatDestroy(), MatMFFDSetFunction(), MatMFFDSetFunctionError(), MatMFFDDSSetUmin()
272:           MatMFFDSetHHistory(), MatMFFDResetHHistory(), MatCreateMFFD(),
273:           MatMFFDGetH(), MatMFFDRegister(), MatMFFDComputeJacobian(), MatSNESMFSetReuseBase(), MatSNESMFGetReuseBase()

275: @*/
276: PetscErrorCode  MatCreateSNESMF(SNES snes,Mat *J)
277: {
279:   PetscInt       n,N;
280:   MatMFFD        mf;

283:   if (snes->vec_func) {
284:     VecGetLocalSize(snes->vec_func,&n);
285:     VecGetSize(snes->vec_func,&N);
286:   } else if (snes->dm) {
287:     Vec tmp;
288:     DMGetGlobalVector(snes->dm,&tmp);
289:     VecGetLocalSize(tmp,&n);
290:     VecGetSize(tmp,&N);
291:     DMRestoreGlobalVector(snes->dm,&tmp);
292:   } else SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Must call SNESSetFunction() or SNESSetDM() first");
293:   MatCreateMFFD(PetscObjectComm((PetscObject)snes),n,n,N,N,J);
294:   MatShellGetContext(*J,&mf);
295:   mf->ctx = snes;

297:   if (snes->npc && snes->npcside== PC_LEFT) {
298:     MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunctionDefaultNPC,snes);
299:   } else {
300:     MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction,snes);
301:   }

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

305:   PetscObjectComposeFunction((PetscObject)*J,"MatMFFDSetBase_C",MatMFFDSetBase_SNESMF);
306:   PetscObjectComposeFunction((PetscObject)*J,"MatSNESMFSetReuseBase_C",MatSNESMFSetReuseBase_SNESMF);
307:   PetscObjectComposeFunction((PetscObject)*J,"MatSNESMFGetReuseBase_C",MatSNESMFGetReuseBase_SNESMF);
308:   return(0);
309: }