1 #include <petsc-private/tsimpl.h> /*I "petscts.h" I*/ 2 3 typedef struct { 4 PetscBool always_accept; 5 PetscReal clip[2]; /* admissible decrease/increase factors */ 6 PetscReal safety; /* safety factor relative to target error */ 7 PetscReal reject_safety; /* extra safety factor if the last step was rejected */ 8 Vec Y; 9 } TSAdapt_Basic; 10 11 #undef __FUNCT__ 12 #define __FUNCT__ "TSAdaptChoose_Basic" 13 static PetscErrorCode TSAdaptChoose_Basic(TSAdapt adapt,TS ts,PetscReal h,PetscInt *next_sc,PetscReal *next_h,PetscBool *accept,PetscReal *wlte) 14 { 15 TSAdapt_Basic *basic = (TSAdapt_Basic*)adapt->data; 16 PetscErrorCode ierr; 17 Vec X,Y; 18 PetscReal enorm,hfac_lte,h_lte,safety; 19 PetscInt order,stepno; 20 21 PetscFunctionBegin; 22 ierr = TSGetTimeStepNumber(ts,&stepno);CHKERRQ(ierr); 23 ierr = TSGetSolution(ts,&X);CHKERRQ(ierr); 24 if (!basic->Y) {ierr = VecDuplicate(X,&basic->Y);CHKERRQ(ierr);} 25 Y = basic->Y; 26 order = adapt->candidates.order[0]; 27 ierr = TSEvaluateStep(ts,order-1,Y,NULL);CHKERRQ(ierr); 28 29 safety = basic->safety; 30 ierr = TSErrorNormWRMS(ts,Y,&enorm);CHKERRQ(ierr); 31 if (enorm > 1.) { 32 if (!*accept) safety *= basic->reject_safety; /* The last attempt also failed, shorten more aggressively */ 33 if (h < (1 + PETSC_SQRT_MACHINE_EPSILON)*adapt->dt_min) { 34 ierr = PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting because step size %g is at minimum\n",(double)enorm,(double)h);CHKERRQ(ierr); 35 *accept = PETSC_TRUE; 36 } else if (basic->always_accept) { 37 ierr = PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting step of size %g because always_accept is set\n",(double)enorm,(double)h);CHKERRQ(ierr); 38 *accept = PETSC_TRUE; 39 } else { 40 ierr = PetscInfo2(adapt,"Estimated scaled local truncation error %g, rejecting step of size %g\n",(double)enorm,(double)h);CHKERRQ(ierr); 41 *accept = PETSC_FALSE; 42 } 43 } else { 44 ierr = PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting step of size %g\n",(double)enorm,(double)h);CHKERRQ(ierr); 45 *accept = PETSC_TRUE; 46 } 47 48 /* The optimal new step based purely on local truncation error for this step. */ 49 hfac_lte = safety * PetscRealPart(PetscPowScalar((PetscScalar)enorm,(PetscReal)(-1./order))); 50 h_lte = h * PetscClipInterval(hfac_lte,basic->clip[0],basic->clip[1]); 51 52 *next_sc = 0; 53 *next_h = PetscClipInterval(h_lte,adapt->dt_min,adapt->dt_max); 54 *wlte = enorm; 55 PetscFunctionReturn(0); 56 } 57 58 #undef __FUNCT__ 59 #define __FUNCT__ "TSAdaptDestroy_Basic" 60 static PetscErrorCode TSAdaptDestroy_Basic(TSAdapt adapt) 61 { 62 TSAdapt_Basic *basic = (TSAdapt_Basic*)adapt->data; 63 PetscErrorCode ierr; 64 65 PetscFunctionBegin; 66 ierr = VecDestroy(&basic->Y);CHKERRQ(ierr); 67 ierr = PetscFree(adapt->data);CHKERRQ(ierr); 68 PetscFunctionReturn(0); 69 } 70 71 #undef __FUNCT__ 72 #define __FUNCT__ "TSAdaptSetFromOptions_Basic" 73 static PetscErrorCode TSAdaptSetFromOptions_Basic(TSAdapt adapt) 74 { 75 TSAdapt_Basic *basic = (TSAdapt_Basic*)adapt->data; 76 PetscErrorCode ierr; 77 PetscInt two; 78 PetscBool set; 79 80 PetscFunctionBegin; 81 ierr = PetscOptionsHead("Basic adaptive controller options");CHKERRQ(ierr); 82 two = 2; 83 ierr = PetscOptionsRealArray("-ts_adapt_basic_clip","Admissible decrease/increase in step size","",basic->clip,&two,&set);CHKERRQ(ierr); 84 if (set && (two != 2 || basic->clip[0] > basic->clip[1])) SETERRQ(PetscObjectComm((PetscObject)adapt),PETSC_ERR_ARG_OUTOFRANGE,"Must give exactly two values to -ts_adapt_basic_clip"); 85 ierr = PetscOptionsReal("-ts_adapt_basic_safety","Safety factor relative to target error","",basic->safety,&basic->safety,NULL);CHKERRQ(ierr); 86 ierr = PetscOptionsReal("-ts_adapt_basic_reject_safety","Extra safety factor to apply if the last step was rejected","",basic->reject_safety,&basic->reject_safety,NULL);CHKERRQ(ierr); 87 ierr = PetscOptionsBool("-ts_adapt_basic_always_accept","Always accept the step regardless of whether local truncation error meets goal","",basic->always_accept,&basic->always_accept,NULL);CHKERRQ(ierr); 88 ierr = PetscOptionsTail();CHKERRQ(ierr); 89 PetscFunctionReturn(0); 90 } 91 92 #undef __FUNCT__ 93 #define __FUNCT__ "TSAdaptView_Basic" 94 static PetscErrorCode TSAdaptView_Basic(TSAdapt adapt,PetscViewer viewer) 95 { 96 TSAdapt_Basic *basic = (TSAdapt_Basic*)adapt->data; 97 PetscErrorCode ierr; 98 PetscBool iascii; 99 100 PetscFunctionBegin; 101 ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr); 102 if (iascii) { 103 if (basic->always_accept) {ierr = PetscViewerASCIIPrintf(viewer," Basic: always accepting steps\n");CHKERRQ(ierr);} 104 ierr = PetscViewerASCIIPrintf(viewer," Basic: clip fastest decrease %g, fastest increase %g\n",(double)basic->clip[0],(double)basic->clip[1]);CHKERRQ(ierr); 105 ierr = PetscViewerASCIIPrintf(viewer," Basic: safety factor %g, extra factor after step rejection %g\n",(double)basic->safety,(double)basic->reject_safety);CHKERRQ(ierr); 106 } 107 PetscFunctionReturn(0); 108 } 109 110 #undef __FUNCT__ 111 #define __FUNCT__ "TSAdaptCreate_Basic" 112 /*MC 113 TSADAPTBASIC - Basic adaptive controller for time stepping 114 115 Level: intermediate 116 117 .seealso: TS, TSAdapt, TSSetAdapt() 118 M*/ 119 PETSC_EXTERN PetscErrorCode TSAdaptCreate_Basic(TSAdapt adapt) 120 { 121 PetscErrorCode ierr; 122 TSAdapt_Basic *a; 123 124 PetscFunctionBegin; 125 ierr = PetscNewLog(adapt,&a);CHKERRQ(ierr); 126 adapt->data = (void*)a; 127 adapt->ops->choose = TSAdaptChoose_Basic; 128 adapt->ops->setfromoptions = TSAdaptSetFromOptions_Basic; 129 adapt->ops->destroy = TSAdaptDestroy_Basic; 130 adapt->ops->view = TSAdaptView_Basic; 131 132 a->clip[0] = 0.1; 133 a->clip[1] = 10.; 134 a->safety = 0.9; 135 a->reject_safety = 0.5; 136 a->always_accept = PETSC_FALSE; 137 PetscFunctionReturn(0); 138 } 139