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 #pragma once 12 13 #include <petscmat.h> /*I "petscmat.h" I*/ 14 #include <petsc/private/petscimpl.h> 15 16 /* 17 Table of functions that manage the computation and understanding 18 of the parameter for finite difference based matrix-free computations 19 */ 20 struct _MFOps { 21 PetscErrorCode (*compute)(MatMFFD, Vec, Vec, PetscScalar *, PetscBool *zeroa); 22 PetscErrorCode (*view)(MatMFFD, PetscViewer); 23 PetscErrorCode (*destroy)(MatMFFD); 24 PetscErrorCode (*setfromoptions)(MatMFFD, PetscOptionItems *); 25 }; 26 27 /* context for default matrix-free SNES */ 28 struct _p_MatMFFD { 29 PETSCHEADER(struct _MFOps); 30 Vec w; /* work vector */ 31 PetscReal error_rel; /* square root of relative error in computing function */ 32 PetscScalar currenth; /* last differencing parameter h used */ 33 PetscScalar *historyh; /* history of differencing parameter h */ 34 PetscInt ncurrenth, maxcurrenth; 35 void *hctx; 36 Mat mat; /* back reference to shell matrix that contains this */ 37 PetscInt recomputeperiod; /* how often the h is recomputed; default to 1 */ 38 PetscInt count; /* used by recomputeperiod */ 39 PetscErrorCode (*checkh)(void *, Vec, Vec, PetscScalar *); 40 void *checkhctx; /* optional context used by MatMFFDSetCheckh() */ 41 42 PetscErrorCode (*func)(void *, Vec, Vec); /* function used for matrix-free */ 43 void *funcctx; /* the context for the function */ 44 Vec current_f; /* location of F(u); used with F(u+h) */ 45 PetscBool current_f_allocated; 46 Vec current_u; /* location of u; used with F(u+h) */ 47 48 PetscErrorCode (*funci)(void *, PetscInt, Vec, PetscScalar *); /* Evaluates func_[i]() */ 49 PetscErrorCode (*funcisetbase)(void *, Vec); /* Sets base for future evaluations of func_[i]() */ 50 51 void *ctx; /* this is used by MatCreateSNESMF() to store the SNES object */ 52 #if defined(PETSC_USE_COMPLEX) 53 PetscBool usecomplex; /* use Lyness complex number trick to compute the matrix-vector product */ 54 #endif 55 }; 56 57 PETSC_EXTERN PetscFunctionList MatMFFDList; 58 PETSC_EXTERN PetscBool MatMFFDRegisterAllCalled; 59 PETSC_EXTERN PetscErrorCode MatMFFDRegisterAll(void); 60