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 6 7 F(x+ha) - F(x) 8 F'(u)a ~= ---------------- 9 h 10 */ 11 12 #if !defined(__MFFD_H__) 13 #define __MFFD_H__ 14 15 #include <petscmat.h> /*I "petscmat.h" I*/ 16 17 /* 18 Table of functions that manage the computation and understanding 19 of the parameter for finite difference based matrix-free computations 20 */ 21 struct _MFOps { 22 PetscErrorCode (*compute)(MatMFFD,Vec,Vec,PetscScalar*,PetscBool * zeroa); 23 PetscErrorCode (*view)(MatMFFD,PetscViewer); 24 PetscErrorCode (*destroy)(MatMFFD); 25 PetscErrorCode (*setfromoptions)(MatMFFD); 26 }; 27 28 struct _p_MatMFFD { /* context for default matrix-free SNES */ 29 PETSCHEADER(struct _MFOps); 30 Vec w; /* work vector */ 31 MatNullSpace sp; /* null space context */ 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() */ 42 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) */ 48 49 PetscErrorCode (*funci)(void*,PetscInt,Vec,PetscScalar*); /* Evaluates func_[i]() */ 50 PetscErrorCode (*funcisetbase)(void*,Vec); /* Sets base for future evaluations of func_[i]() */ 51 52 PetscScalar vscale,vshift; /* diagonal scale and shift by scalars */ 53 Vec dlscale,drscale,dshift; /* diagonal scale and shift by vectors */ 54 }; 55 56 extern PetscFunctionList MatMFFDList; 57 extern PetscBool MatMFFDRegisterAllCalled; 58 59 #endif 60