Efficient RK4, as provided by Yosef Zlochower.

git-svn-id: http://svn.cactuscode.org/arrangements/CactusNumerical/MoL/trunk@113 578cdeb0-5ea1-4b81-8215-5a3b8777ee0b

1 files changed, 16 insertions, 0 deletions

diff --git a/src/SetTime.c b/src/SetTime.c
index 3e9ae3f..5149eb2 100644
--- a/src/SetTime.c
+++ b/src/SetTime.c
@@ -247,6 +247,22 @@ int MoL_ResetTime(CCTK_ARGUMENTS)
         0.5*(*Original_Delta_Time)/cctkGH->cctk_timefac;
     }
   }
+  else if (CCTK_EQUALS(ODE_Method,"RK4"))
+  {
+    const int substep = MoL_Intermediate_Steps - (* MoL_Intermediate_Step);
+
+    CCTK_REAL dt = (*Original_Delta_Time)/cctkGH->cctk_timefac;
+    switch (substep)
+    {
+      case 1:
+      case 2:
+        dt *= 0.5;
+        break;
+      default:
+        dt = 0;
+    }
+    cctkGH->cctk_time = (*Original_Time) - dt;
+  }
   else if (CCTK_EQUALS(ODE_Method,"RK45") || CCTK_EQUALS(ODE_Method,"RK45CK"))
   {
     const int substep = MoL_Intermediate_Steps - (* MoL_Intermediate_Step);