Date: 2015-10-02T22:10:36+00:00

Actual source code: mffdimpl.h
petsc-3.6.2 2015-10-02
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      1: /*
      2:     This file should be included in NEW routines that compute the
      3:     differencing parameter for finite difference based matrix-free
      4:     methods.  For example, such routines can compute h for use in
      5:     Jacobian-vector products of the form

      7:                        F(x+ha) - F(x)
      8:           F'(u)a  ~=  ----------------
      9:                             h
     10: */

     15: #include <petscmat.h>         /*I  "petscmat.h"   I*/
     16: #include <petsc/private/petscimpl.h>

     18: /*
     19:     Table of functions that manage the computation and understanding
     20:     of the parameter for finite difference based matrix-free computations
     21: */
     22: struct _MFOps {
     23:   PetscErrorCode (*compute)(MatMFFD,Vec,Vec,PetscScalar*,PetscBool * zeroa);
     24:   PetscErrorCode (*view)(MatMFFD,PetscViewer);
     25:   PetscErrorCode (*destroy)(MatMFFD);
     26:   PetscErrorCode (*setfromoptions)(PetscOptions*,MatMFFD);
     27: };

     29: struct _p_MatMFFD {    /* context for default matrix-free SNES */
     30:   PETSCHEADER(struct _MFOps);
     31:   Vec            w;                        /* work vector */
     32:   PetscReal      error_rel;                /* square root of relative error in computing function */
     33:   PetscScalar    currenth;                 /* last differencing parameter h used */
     34:   PetscScalar    *historyh;                /* history of differencing parameter h */
     35:   PetscInt       ncurrenth,maxcurrenth;
     36:   void           *hctx;
     37:   Mat            mat;                      /* back reference to shell matrix that contains this */
     38:   PetscInt       recomputeperiod;          /* how often the h is recomputed; default to 1 */
     39:   PetscInt       count;                    /* used by recomputeperiod */
     40:   PetscErrorCode (*checkh)(void*,Vec,Vec,PetscScalar*);
     41:   void           *checkhctx;               /* optional context used by MatMFFDSetCheckh() */

     43:   PetscErrorCode (*func)(void*,Vec,Vec);    /* function used for matrix free */
     44:   void           *funcctx;                       /* the context for the function */
     45:   Vec            current_f;                      /* location of F(u); used with F(u+h) */
     46:   PetscBool      current_f_allocated;
     47:   Vec            current_u;                      /* location of u; used with F(u+h) */

     49:   PetscErrorCode (*funci)(void*,PetscInt,Vec,PetscScalar*);    /* Evaluates func_[i]() */
     50:   PetscErrorCode (*funcisetbase)(void*,Vec);              /* Sets base for future evaluations of func_[i]() */

     52:   PetscScalar vscale,vshift;                   /* diagonal scale and shift by scalars */
     53:   Vec         dlscale,drscale,dshift;                   /* diagonal scale and shift by vectors */
     54:   void        *ctx;   /* this is used by MatCreateSNESMF() to store the SNES object */
     55: };

     57: PETSC_EXTERN PetscFunctionList MatMFFDList;
     58: PETSC_EXTERN PetscBool         MatMFFDRegisterAllCalled;
     59: PETSC_EXTERN PetscErrorCode    MatMFFDRegisterAll(void);

     61: #endif