From e76b9ee4215de4ca9258261646421ef2adfd2c19 Mon Sep 17 00:00:00 2001
From: hawke <hawke@578cdeb0-5ea1-4b81-8215-5a3b8777ee0b>
Date: Thu, 24 Aug 2006 11:45:17 +0000
Subject: Theta ICN. Patch from Frank Loeffler.

git-svn-id: http://svn.cactuscode.org/arrangements/CactusNumerical/MoL/trunk@120 578cdeb0-5ea1-4b81-8215-5a3b8777ee0b
---
 param.ccl |  9 +++++++++
 src/ICN.c | 22 ++++++++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/param.ccl b/param.ccl
index bd8e86f..7e29e56 100644
--- a/param.ccl
+++ b/param.ccl
@@ -102,6 +102,15 @@ KEYWORD Generic_Type "If using the generic method, which sort"
   "Classic RK3"	:: "Efficient RK3 - classical version"
 } "RK"
 
+CCTK_REAL ICN_avg_theta "theta of averaged ICN method, usually 0.5"
+{
+  0:1 :: "0 <= theta <= 1"
+} 0.5
+
+BOOLEAN ICN_avg_swapped "Use swapped averages in ICN method?"
+{
+} "no"
+
 CCTK_INT MoL_Intermediate_Steps "Number of intermediate steps taken by the ODE method"
 {
   1:*		:: "Anything greater than 1"
diff --git a/src/ICN.c b/src/ICN.c
index 7e0acde..7f75a35 100644
--- a/src/ICN.c
+++ b/src/ICN.c
@@ -221,6 +221,8 @@ void MoL_ICNAverage(CCTK_ARGUMENTS)
   
   /* FIXME */
 
+  CCTK_REAL theta;
+
 #ifdef MOLDOESCOMPLEX
 
   CCTK_COMPLEX *OldComplexVar;
@@ -230,15 +232,23 @@ void MoL_ICNAverage(CCTK_ARGUMENTS)
 
 #endif
 
+   
+  theta = ICN_avg_theta;
+  if (ICN_avg_swapped && (*MoL_Intermediate_Step%2))
+  {
+    theta = 1.0 - theta;
+  }
+
 #ifdef MOLDEBUG
   printf("Inside ICN.\nProcessor %d.\nStep %d.\nRefinement %d.\n"
-         "Timestep %g.\nSpacestep %g.\nTime %g\n",
+         "Timestep %g.\nSpacestep %g.\nTime %g Theta %g\n",
          CCTK_MyProc(cctkGH),
          MoL_Intermediate_Steps - *MoL_Intermediate_Step + 1,
          *cctk_levfac,
          CCTK_DELTA_TIME,
          CCTK_DELTA_SPACE(0),
-         cctk_time);
+         cctk_time,
+         theta);
 #endif  
 
   totalsize = 1;
@@ -261,7 +271,9 @@ void MoL_ICNAverage(CCTK_ARGUMENTS)
     
     for (index = 0; index < totalsize; index++)
     {
-      UpdateVar[index] = 0.5 * (UpdateVar[index] + OldVar[index]);
+/*       UpdateVar[index] = 0.5 * (UpdateVar[index] + OldVar[index]); */
+      UpdateVar[index] = (1.0 - theta) * UpdateVar[index] + 
+                                theta  * OldVar[index];
     }
   }
   
@@ -292,7 +304,9 @@ void MoL_ICNAverage(CCTK_ARGUMENTS)
 
     for (index = 0; index < arraytotalsize; index++)
     {
-      UpdateVar[index] = 0.5 * (UpdateVar[index] + OldVar[index]);
+/*       UpdateVar[index] = 0.5 * (UpdateVar[index] + OldVar[index]); */
+      UpdateVar[index] = (1.0 - theta) * UpdateVar[index] + 
+                                theta  * OldVar[index];
     }
   }
 
-- 
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