Actual source code: adaptbasic.c

      1: #include <petsc/private/tsimpl.h>
      2: #include <petscdm.h>

      4: static PetscErrorCode TSAdaptChoose_Basic(TSAdapt adapt,TS ts,PetscReal h,PetscInt *next_sc,PetscReal *next_h,PetscBool *accept,PetscReal *wlte,PetscReal *wltea,PetscReal *wlter)
      5: {
      6:   Vec            Y;
      7:   DM             dm;
      8:   PetscInt       order  = PETSC_DECIDE;
      9:   PetscReal      enorm  = -1;
     10:   PetscReal      enorma,enormr;
     11:   PetscReal      safety = adapt->safety;
     12:   PetscReal      hfac_lte,h_lte;

     16:   *next_sc = 0;   /* Reuse the same order scheme */
     17:   *wltea   = -1;  /* Weighted absolute local truncation error is not used */
     18:   *wlter   = -1;  /* Weighted relative local truncation error is not used */

     20:   if (ts->ops->evaluatewlte) {
     21:     TSEvaluateWLTE(ts,adapt->wnormtype,&order,&enorm);
     22:     if (enorm >= 0 && order < 1) SETERRQ1(PetscObjectComm((PetscObject)adapt),PETSC_ERR_ARG_OUTOFRANGE,"Computed error order %D must be positive",order);
     23:   } else if (ts->ops->evaluatestep) {
     24:     if (adapt->candidates.n < 1) SETERRQ(PetscObjectComm((PetscObject)adapt),PETSC_ERR_ARG_WRONGSTATE,"No candidate has been registered");
     25:     if (!adapt->candidates.inuse_set) SETERRQ1(PetscObjectComm((PetscObject)adapt),PETSC_ERR_ARG_WRONGSTATE,"The current in-use scheme is not among the %D candidates",adapt->candidates.n);
     26:     order = adapt->candidates.order[0];
     27:     TSGetDM(ts,&dm);
     28:     DMGetGlobalVector(dm,&Y);
     29:     TSEvaluateStep(ts,order-1,Y,NULL);
     30:     TSErrorWeightedNorm(ts,ts->vec_sol,Y,adapt->wnormtype,&enorm,&enorma,&enormr);
     31:     DMRestoreGlobalVector(dm,&Y);
     32:   }

     34:   if (enorm < 0) {
     35:     *accept  = PETSC_TRUE;
     36:     *next_h  = h;            /* Reuse the old step */
     37:     *wlte    = -1;           /* Weighted local truncation error was not evaluated */
     38:     return(0);
     39:   }

     41:   /* Determine whether the step is accepted of rejected */
     42:   if (enorm > 1) {
     43:     if (!*accept) safety *= adapt->reject_safety; /* The last attempt also failed, shorten more aggressively */
     44:     if (h < (1 + PETSC_SQRT_MACHINE_EPSILON)*adapt->dt_min) {
     45:       PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting because step size %g is at minimum\n",(double)enorm,(double)h);
     46:       *accept = PETSC_TRUE;
     47:     } else if (adapt->always_accept) {
     48:       PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting step of size %g because always_accept is set\n",(double)enorm,(double)h);
     49:       *accept = PETSC_TRUE;
     50:     } else {
     51:       PetscInfo2(adapt,"Estimated scaled local truncation error %g, rejecting step of size %g\n",(double)enorm,(double)h);
     52:       *accept = PETSC_FALSE;
     53:     }
     54:   } else {
     55:     PetscInfo2(adapt,"Estimated scaled local truncation error %g, accepting step of size %g\n",(double)enorm,(double)h);
     56:     *accept = PETSC_TRUE;
     57:   }

     59:   /* The optimal new step based purely on local truncation error for this step. */
     60:   if (enorm > 0)
     61:     hfac_lte = safety * PetscPowReal(enorm,((PetscReal)-1)/order);
     62:   else
     63:     hfac_lte = safety * PETSC_INFINITY;
     64:   if (adapt->timestepjustdecreased){
     65:     hfac_lte = PetscMin(hfac_lte,1.0);
     66:     adapt->timestepjustdecreased--;
     67:   }
     68:   h_lte = h * PetscClipInterval(hfac_lte,adapt->clip[0],adapt->clip[1]);

     70:   *next_h = PetscClipInterval(h_lte,adapt->dt_min,adapt->dt_max);
     71:   *wlte   = enorm;
     72:   return(0);
     73: }

     75: /*MC
     76:    TSADAPTBASIC - Basic adaptive controller for time stepping

     78:    Level: intermediate

     80: .seealso: TS, TSAdapt, TSGetAdapt()
     81: M*/
     82: PETSC_EXTERN PetscErrorCode TSAdaptCreate_Basic(TSAdapt adapt)
     83: {
     85:   adapt->ops->choose = TSAdaptChoose_Basic;
     86:   return(0);
     87: }