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: }