1 #include <petsc-private/linesearchimpl.h> 2 #include <petsc-private/snesimpl.h> 3 4 #undef __FUNCT__ 5 #define __FUNCT__ "SNESLineSearchApply_Basic" 6 static PetscErrorCode SNESLineSearchApply_Basic(SNESLineSearch linesearch) 7 { 8 PetscBool changed_y, changed_w; 9 PetscErrorCode ierr; 10 Vec X, F, Y, W; 11 SNES snes; 12 PetscReal gnorm, xnorm, ynorm, lambda; 13 PetscBool domainerror; 14 15 PetscFunctionBegin; 16 17 ierr = SNESLineSearchGetVecs(linesearch, &X, &F, &Y, &W, PETSC_NULL);CHKERRQ(ierr); 18 ierr = SNESLineSearchGetNorms(linesearch, &xnorm, &gnorm, &ynorm);CHKERRQ(ierr); 19 ierr = SNESLineSearchGetLambda(linesearch, &lambda);CHKERRQ(ierr); 20 ierr = SNESLineSearchGetSNES(linesearch, &snes);CHKERRQ(ierr); 21 ierr = SNESLineSearchSetSuccess(linesearch, PETSC_TRUE);CHKERRQ(ierr); 22 23 /* precheck */ 24 ierr = SNESLineSearchPreCheck(linesearch,X,Y,&changed_y);CHKERRQ(ierr); 25 26 /* update */ 27 ierr = VecWAXPY(W,-lambda,Y,X);CHKERRQ(ierr); 28 if (linesearch->ops->viproject) { 29 ierr = (*linesearch->ops->viproject)(snes, W);CHKERRQ(ierr); 30 } 31 32 /* postcheck */ 33 ierr = SNESLineSearchPostCheck(linesearch,X,Y,W,&changed_y,&changed_w);CHKERRQ(ierr); 34 if (changed_y) { 35 ierr = VecWAXPY(W,-lambda,Y,X);CHKERRQ(ierr); 36 if (linesearch->ops->viproject) { 37 ierr = (*linesearch->ops->viproject)(snes, W);CHKERRQ(ierr); 38 } 39 } 40 if (linesearch->norms || snes->iter < snes->max_its-1) { 41 ierr = SNESComputeFunction(snes,W,F);CHKERRQ(ierr); 42 ierr = SNESGetFunctionDomainError(snes, &domainerror);CHKERRQ(ierr); 43 if (domainerror) { 44 ierr = SNESLineSearchSetSuccess(linesearch, PETSC_FALSE);CHKERRQ(ierr); 45 PetscFunctionReturn(0); 46 } 47 } 48 49 if (linesearch->norms) { 50 if (!linesearch->ops->vinorm) VecNormBegin(F, NORM_2, &linesearch->fnorm); 51 ierr = VecNormBegin(Y, NORM_2, &linesearch->ynorm);CHKERRQ(ierr); 52 ierr = VecNormBegin(W, NORM_2, &linesearch->xnorm);CHKERRQ(ierr); 53 if (!linesearch->ops->vinorm) VecNormEnd(F, NORM_2, &linesearch->fnorm); 54 ierr = VecNormEnd(Y, NORM_2, &linesearch->ynorm);CHKERRQ(ierr); 55 ierr = VecNormEnd(W, NORM_2, &linesearch->xnorm);CHKERRQ(ierr); 56 57 if (linesearch->ops->vinorm) { 58 linesearch->fnorm = gnorm; 59 ierr = (*linesearch->ops->vinorm)(snes, F, W, &linesearch->fnorm);CHKERRQ(ierr); 60 } else { 61 ierr = VecNorm(F,NORM_2,&linesearch->fnorm);CHKERRQ(ierr); 62 } 63 } 64 65 /* copy the solution over */ 66 ierr = VecCopy(W, X);CHKERRQ(ierr); 67 PetscFunctionReturn(0); 68 } 69 70 #undef __FUNCT__ 71 #define __FUNCT__ "SNESLineSearchCreate_Basic" 72 /*MC 73 SNESLINESEARCHBASIC - This line search implementation is not a line 74 search at all; it simply uses the full step. Thus, this routine is intended 75 for methods with well-scaled updates; i.e. Newton's method (SNESNEWTONLS), on 76 well-behaved problems. 77 78 Options Database Keys: 79 + -snes_linesearch_damping (1.0) damping parameter. 80 - -snes_linesearch_norms (true) whether to compute norms or not. 81 82 Notes: 83 For methods with ill-scaled updates (SNESNRICHARDSON, SNESNCG), a small 84 damping parameter may yield satisfactory but slow convergence despite 85 the simplicity of the line search. 86 87 Level: advanced 88 89 .keywords: SNES, SNESLineSearch, damping 90 91 .seealso: SNESLineSearchCreate(), SNESLineSearchSetType() 92 M*/ 93 PETSC_EXTERN_C PetscErrorCode SNESLineSearchCreate_Basic(SNESLineSearch linesearch) 94 { 95 PetscFunctionBegin; 96 linesearch->ops->apply = SNESLineSearchApply_Basic; 97 linesearch->ops->destroy = PETSC_NULL; 98 linesearch->ops->setfromoptions = PETSC_NULL; 99 linesearch->ops->reset = PETSC_NULL; 100 linesearch->ops->view = PETSC_NULL; 101 linesearch->ops->setup = PETSC_NULL; 102 PetscFunctionReturn(0); 103 } 104