Actual source code: adaptcfl.c
petsc-3.10.5 2019-03-28
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      1:  #include <petsc/private/tsimpl.h>

      3: static PetscErrorCode TSAdaptChoose_CFL(TSAdapt adapt,TS ts,PetscReal h,PetscInt *next_sc,PetscReal *next_h,PetscBool *accept,PetscReal *wlte,PetscReal *wltea,PetscReal *wlter)
      4: {
      5:   PetscErrorCode  ierr;
      6:   PetscReal       hcfl,cfltimestep,ccfl;
      7:   PetscInt        ncandidates;
      8:   const PetscReal *ccflarray;

     11:   TSGetCFLTime(ts,&cfltimestep);
     12:   TSAdaptCandidatesGet(adapt,&ncandidates,NULL,NULL,&ccflarray,NULL);
     13:   ccfl = (ncandidates > 0) ? ccflarray[0] : 1.0;

     15:   if (!adapt->always_accept) SETERRQ(PetscObjectComm((PetscObject)adapt),PETSC_ERR_SUP,"Step rejection not implemented. The CFL implementation is incomplete/unusable");

     17:   /* Determine whether the step is accepted of rejected */
     18:   *accept = PETSC_TRUE;
     19:   if (h > cfltimestep * ccfl) {
     20:     if (adapt->always_accept) {
     21:       PetscInfo3(adapt,"Step length %g with scheme of CFL coefficient %g did not satisfy user-provided CFL constraint %g, proceeding anyway\n",(double)h,(double)ccfl,(double)cfltimestep);
     22:     } else {
     23:       PetscInfo3(adapt,"Step length %g with scheme of CFL coefficient %g did not satisfy user-provided CFL constraint %g, step REJECTED\n",(double)h,(double)ccfl,(double)cfltimestep);
     24:       *accept  = PETSC_FALSE;
     25:     }
     26:   }

     28:   /* The optimal new step based purely on CFL constraint for this step. */
     29:   hcfl = adapt->safety * cfltimestep * ccfl;
     30:   if (hcfl < adapt->dt_min) {
     31:     PetscInfo4(adapt,"Cannot satisfy CFL constraint %g (with %g safety) at minimum time step %g with method coefficient %g, proceding anyway\n",(double)cfltimestep,(double)adapt->safety,(double)adapt->dt_min,(double)ccfl);
     32:   }

     34:   *next_sc = 0;
     35:   *next_h  = PetscClipInterval(hcfl,adapt->dt_min,adapt->dt_max);
     36:   *wlte    = -1;   /* Weighted local truncation error was not evaluated */
     37:   *wltea   = -1;   /* Weighted absolute local truncation error was not evaluated */
     38:   *wlter   = -1;   /* Weighted relative local truncation error was not evaluated */
     39:   return(0);
     40: }

     42: /*MC
     43:    TSADAPTCFL - CFL adaptive controller for time stepping

     45:    Level: intermediate

     47: .seealso: TS, TSAdapt, TSGetAdapt()
     48: M*/
     49: PETSC_EXTERN PetscErrorCode TSAdaptCreate_CFL(TSAdapt adapt)
     50: {
     52:   adapt->ops->choose = TSAdaptChoose_CFL;
     53:   return(0);
     54: }