From 9ad75f1b1648057d41cb96409acd05c19bb01aa9 Mon Sep 17 00:00:00 2001
From: allen <allen@5633253d-7678-4964-a54d-f87795f8ee59>
Date: Tue, 19 Oct 1999 16:41:35 +0000
Subject: Generic courant timestep ... not linked to anything yet

git-svn-id: http://svn.cactuscode.org/arrangements/CactusBase/Time/trunk@9 5633253d-7678-4964-a54d-f87795f8ee59
---
 src/Courant.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 src/Courant.c

diff --git a/src/Courant.c b/src/Courant.c
new file mode 100644
index 0000000..82f3557
--- /dev/null
+++ b/src/Courant.c
@@ -0,0 +1,80 @@
+ /*@@
+   @file      Courant.c
+   @date      September 4 1999
+   @author    Gabrielle Allen
+   @desc 
+   Specification of timestep using Courant condition
+   @enddesc 
+ @@*/
+
+#include <malloc.h>
+#include <math.h>
+
+#include "cctk.h"
+#include "cctk_arguments.h"
+#include "cctk_parameters.h"
+
+void Time_Courant(CCTK_CARGUMENTS)
+{
+  DECLARE_CCTK_PARAMETERS
+  DECLARE_CCTK_CARGUMENTS
+
+  CCTK_REAL min_spacing;
+  CCTK_REAL courant_speed;
+
+  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 */
+  courant_speed = *wave_speed;
+  *courant_dt = courant_fac/courant_speed/sqrt((CCTK_REAL )cctk_dim);
+
+  /* Output timestep if required */
+
+  if (outcourant_every > 0 && cctk_iteration%outcourant_every == 0)
+  { 
+    CCTK_OutputVarAsByMethod(cctkGH,"time::courant_dt","Scalar","courant");
+  }
+
+  /* Set the Cactus timestep */
+
+  if (! courant_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/courant_wave_speed;
+  }
+
+}
+
+
+
-- 
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