/*@@
   @file      Courant.c
   @date      September 4 1999
   @author    Gabrielle Allen
   @desc 
   Specification of timestep using Courant condition
   @enddesc 
 @@*/

#include <stdlib.h>
#include <math.h>

#include "cctk.h"
#include "cctk_Arguments.h"
#include "cctk_Parameters.h"

static char *rcsid = "$Header$";

CCTK_FILEVERSION(CactusBase_Time_Courant_c)

void Time_Courant(CCTK_ARGUMENTS);

void Time_Courant(CCTK_ARGUMENTS)
{
  DECLARE_CCTK_PARAMETERS
  DECLARE_CCTK_ARGUMENTS

  CCTK_REAL min_spacing=0;

  char *message;

  /* Calculate the minimum grid spacing */
  if (cctk_dim>=1)
  {
    min_spacing = cctk_delta_space[0];
  }

  if (cctk_dim>=2)
  {
    min_spacing = (min_spacing<cctk_delta_space[1] ?
	min_spacing : cctk_delta_space[1]);
  }
  
  if (cctk_dim>=3)
  {
    min_spacing = (min_spacing<cctk_delta_space[2] ?
	min_spacing : cctk_delta_space[2]);
  }
  
  if (cctk_dim>=4)
  {
    CCTK_WARN(0,"Time Step not defined for greater than 4 dimensions");
  }

  /* Calculate the courant timestep */
  if (CCTK_Equals(timestep_method,"courant_time"))
  {
    *courant_dt = courant_fac*(*courant_min_time)/sqrt((CCTK_REAL )cctk_dim);
  }
  else if (CCTK_Equals(timestep_method,"courant_speed"))
  {
    *courant_dt = courant_fac/(*courant_wave_speed)/sqrt((CCTK_REAL )cctk_dim);
  }

  /* Set the Cactus timestep */

  if (! timestep_outonly)
  {
    cctkGH->cctk_delta_time = *courant_dt;

    message = (char *)malloc(1024*sizeof(char));
    sprintf(message,"Time step set to %f",cctkGH->cctk_delta_time);
    CCTK_INFO(message);
    free(message);

  }
  else
  {
      cctkGH->cctk_delta_time = dtfac*min_spacing;
  }

  
  

}