1 2 #include <petsc/private/snesimpl.h> /*I "petscsnes.h" I*/ 3 #include <petscdm.h> /*I "petscdm.h" I*/ 4 5 /* 6 MatFDColoringSetFunction() takes a function with four arguments, we want to use SNESComputeFunction() 7 since it logs function computation information. 8 */ 9 static PetscErrorCode SNESComputeFunctionCtx(SNES snes, Vec x, Vec f, void *ctx) { 10 return SNESComputeFunction(snes, x, f); 11 } 12 static PetscErrorCode SNESComputeMFFunctionCtx(SNES snes, Vec x, Vec f, void *ctx) { 13 return SNESComputeMFFunction(snes, x, f); 14 } 15 16 /*@C 17 SNESComputeJacobianDefaultColor - Computes the Jacobian using 18 finite differences and coloring to exploit matrix sparsity. 19 20 Collective on SNES 21 22 Input Parameters: 23 + snes - nonlinear solver object 24 . x1 - location at which to evaluate Jacobian 25 - ctx - MatFDColoring context or NULL 26 27 Output Parameters: 28 + J - Jacobian matrix (not altered in this routine) 29 - B - newly computed Jacobian matrix to use with preconditioner (generally the same as J) 30 31 Level: intermediate 32 33 Options Database Key: 34 + -snes_fd_color_use_mat - use a matrix coloring from the explicit matrix nonzero pattern instead of from the DM providing the matrix 35 . -snes_fd_color - Activates SNESComputeJacobianDefaultColor() in SNESSetFromOptions() 36 . -mat_fd_coloring_err <err> - Sets <err> (square root of relative error in the function) 37 . -mat_fd_coloring_umin <umin> - Sets umin, the minimum allowable u-value magnitude 38 . -mat_fd_type - Either wp or ds (see MATMFFD_WP or MATMFFD_DS) 39 . -snes_mf_operator - Use matrix free application of Jacobian 40 - -snes_mf - Use matrix free Jacobian with no explicit Jacobian representation 41 42 Notes: 43 If the coloring is not provided through the context, this will first try to get the 44 coloring from the DM. If the DM type has no coloring routine, then it will try to 45 get the coloring from the matrix. This requires that the matrix have nonzero entries 46 precomputed. 47 48 SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix free via SNESSetUseMatrixFree(), 49 and computing explicitly with finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation 50 and the MatFDColoring object, see src/ts/tutorials/autodiff/ex16adj_tl.cxx 51 52 .seealso: `SNESSetJacobian()`, `SNESTestJacobian()`, `SNESComputeJacobianDefault()`, `SNESSetUseMatrixFree()`, 53 `MatFDColoringCreate()`, `MatFDColoringSetFunction()` 54 55 @*/ 56 PetscErrorCode SNESComputeJacobianDefaultColor(SNES snes, Vec x1, Mat J, Mat B, void *ctx) { 57 MatFDColoring color = (MatFDColoring)ctx; 58 DM dm; 59 MatColoring mc; 60 ISColoring iscoloring; 61 PetscBool hascolor; 62 PetscBool solvec, matcolor = PETSC_FALSE; 63 DMSNES dms; 64 65 PetscFunctionBegin; 66 if (color) PetscValidHeaderSpecific(color, MAT_FDCOLORING_CLASSID, 5); 67 if (!color) PetscCall(PetscObjectQuery((PetscObject)B, "SNESMatFDColoring", (PetscObject *)&color)); 68 69 if (!color) { 70 PetscCall(SNESGetDM(snes, &dm)); 71 PetscCall(DMHasColoring(dm, &hascolor)); 72 matcolor = PETSC_FALSE; 73 PetscCall(PetscOptionsGetBool(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_fd_color_use_mat", &matcolor, NULL)); 74 if (hascolor && !matcolor) { 75 PetscCall(DMCreateColoring(dm, IS_COLORING_GLOBAL, &iscoloring)); 76 } else { 77 PetscCall(MatColoringCreate(B, &mc)); 78 PetscCall(MatColoringSetDistance(mc, 2)); 79 PetscCall(MatColoringSetType(mc, MATCOLORINGSL)); 80 PetscCall(MatColoringSetFromOptions(mc)); 81 PetscCall(MatColoringApply(mc, &iscoloring)); 82 PetscCall(MatColoringDestroy(&mc)); 83 } 84 PetscCall(MatFDColoringCreate(B, iscoloring, &color)); 85 PetscCall(DMGetDMSNES(dm, &dms)); 86 if (dms->ops->computemffunction) { 87 PetscCall(MatFDColoringSetFunction(color, (PetscErrorCode(*)(void))SNESComputeMFFunctionCtx, NULL)); 88 } else { 89 PetscCall(MatFDColoringSetFunction(color, (PetscErrorCode(*)(void))SNESComputeFunctionCtx, NULL)); 90 } 91 PetscCall(MatFDColoringSetFromOptions(color)); 92 PetscCall(MatFDColoringSetUp(B, iscoloring, color)); 93 PetscCall(ISColoringDestroy(&iscoloring)); 94 PetscCall(PetscObjectCompose((PetscObject)B, "SNESMatFDColoring", (PetscObject)color)); 95 PetscCall(PetscObjectDereference((PetscObject)color)); 96 } 97 98 /* F is only usable if there is no RHS on the SNES and the full solution corresponds to x1 */ 99 PetscCall(VecEqual(x1, snes->vec_sol, &solvec)); 100 if (!snes->vec_rhs && solvec) { 101 Vec F; 102 PetscCall(SNESGetFunction(snes, &F, NULL, NULL)); 103 PetscCall(MatFDColoringSetF(color, F)); 104 } 105 PetscCall(MatFDColoringApply(B, color, x1, snes)); 106 if (J != B) { 107 PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY)); 108 PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY)); 109 } 110 PetscFunctionReturn(0); 111 } 112