Symmetry registration and boundary condition is moved from Einstein to

here.

Reworked the grid routines to allow grid points to be on the axes
depending on the parameter no_origin (defaults to not on the origin).
Added more parameter checking


git-svn-id: http://svn.cactuscode.org/arrangements/CactusBase/CartGrid3D/trunk@30 c78560ca-4b45-4335-b268-5f3340f3cb52

11 files changed, 629 insertions, 53 deletions

diff --git a/param.ccl b/param.ccl
index 222574a..60a0873 100644
--- a/param.ccl
+++ b/param.ccl
@@ -1,6 +1,14 @@
 # Parameter definitions for thorn CartGrid3D
 # $Header$
 
+private:
+
+LOGICAL no_origin "Don't place grid points on the coordinate origin/axes"
+{
+ : ::
+} "yes"
+
+
 protected:
 
 REAL dx "Coarse grid spacing in x-direction"
diff --git a/schedule.ccl b/schedule.ccl
index 56bf97f..bec8510 100644
--- a/schedule.ccl
+++ b/schedule.ccl
@@ -3,6 +3,11 @@
 
 STORAGE: coordinates
 
+schedule SymmetryStartup at CCTK_STARTUP
+{
+  LANG: C
+} "Register GH Extension for GridSymmetry"
+
 schedule RegisterCartGrid3DCoords at CCTK_STARTUP
 {
   LANG:C
diff --git a/src/ApplySymmetry.c b/src/ApplySymmetry.c
new file mode 100644
index 0000000..a0b5ba3
--- /dev/null
+++ b/src/ApplySymmetry.c
@@ -0,0 +1,58 @@
+
+/*@@
+   @routine    FortranSym
+   @date       Mon Mar 15 15:51:57 1999
+   @author     Gerd Lanfermann
+   @desc 
+               Routine performs the symmetry boundary operations.
+   @enddesc 
+   @calls     
+   @calledby   
+   @history 
+ 
+   @endhistory 
+@@*/
+
+       subroutine FortranSym(nxyz,var,nghostzones,sym,doSym)
+
+      implicit none
+
+      INTEGER nxyz(3)
+      CCTK_REAL    var(nxyz(1),nxyz(2),nxyz(3))
+      INTEGER nghostzones
+      INTEGER sym(3)
+      INTEGER doSym(3)
+      
+      INTEGER sw
+      
+c      Apply symmetry if 
+c       * the grid chunk has a physical boundary (bbox)
+c       * its size in a direction is bigger than one (sh)
+c       * we actually want a symmetry (sx.ne.ESYM_UNSET)
+
+      if (doSym(1) == 1) then
+
+         do sw=1, nghostzones
+            var(sw,:,:) = sym(1)*var(nghostzones+sw,:,:)
+         end do
+
+      end if
+
+      if (doSym(2) == 1) then
+
+         do sw=1, nghostzones    
+            var(:,sw,:) = sym(2)*var(:,nghostzones+sw,:) 
+         end do
+
+      end if
+
+      if (doSym(3).eq.1) then
+
+         do sw=1, nghostzones
+            var(:,:,sw) = sym(3)*var(:,:,nghostzones+sw)
+         end do
+
+      end if
+
+      end subroutine
+
diff --git a/src/CartGrid3D.F b/src/CartGrid3D.F
index 2b77a9e..3b98f95 100644
--- a/src/CartGrid3D.F
+++ b/src/CartGrid3D.F
@@ -22,13 +22,11 @@
       DECLARE_PARAMETERS
 
       integer :: CCTK_Equals
-      integer :: iflag, iconv, i, j, k
+      integer :: iconv, i, j, k
       CCTK_REAL :: x_origin,y_origin,z_origin
       CCTK_REAL :: this_dx,this_dy,this_dz
       CCTK_REAL :: xmax1,ymax1,zmax1
 
-      iflag = 0  ! Gets set to one if we set a grid
-
       iconv = 2**(cctk_convlevel-1)
  
 c     --------------------------------------------------------------
@@ -57,12 +55,18 @@ c     --------------------------------------------------------------
          if (CCTK_Equals(symmetry,'octant') == 1) then
 
             call CCTK_Info("Octant symmetry")
-            iflag = iflag +1
 
 c           Grid spacing on coarsest grid          
-            coarse_dx = xmax/(DBLE(cctk_gsh(1))-1.5d0)
-            coarse_dy = ymax/(DBLE(cctk_gsh(2))-1.5d0)
-            coarse_dz = zmax/(DBLE(cctk_gsh(3))-1.5d0)
+
+            if (no_origin==1) then
+               coarse_dx = xmax/(DBLE(cctk_gsh(1))-1.5d0)
+               coarse_dy = ymax/(DBLE(cctk_gsh(2))-1.5d0)
+               coarse_dz = zmax/(DBLE(cctk_gsh(3))-1.5d0)
+            else
+               coarse_dx = xmax/(DBLE(cctk_gsh(1))-1.0d0)
+               coarse_dy = ymax/(DBLE(cctk_gsh(2))-1.0d0)
+               coarse_dz = zmax/(DBLE(cctk_gsh(3))-1.0d0)
+            end if
 
 c           Grid spacing on this grid
             this_dx = coarse_dx/cctk_levfac(1)
@@ -70,24 +74,26 @@ c           Grid spacing on this grid
             this_dz = coarse_dz/cctk_levfac(3)
 
 c           Minimum coordinate values on this grid
-            x_origin = (0.5-dble(cctk_nghostzones(1)))*this_dx
-            y_origin = (0.5-dble(cctk_nghostzones(2)))*this_dy
-            z_origin = (0.5-dble(cctk_nghostzones(3)))*this_dz
+            if (no_origin==1) then
+               x_origin = (0.5-dble(cctk_nghostzones(1)))*this_dx
+               y_origin = (0.5-dble(cctk_nghostzones(2)))*this_dy
+               z_origin = (0.5-dble(cctk_nghostzones(3)))*this_dz
+            else
+               x_origin = (-dble(cctk_nghostzones(1)))*this_dx
+               y_origin = (-dble(cctk_nghostzones(2)))*this_dy
+               z_origin = (-dble(cctk_nghostzones(3)))*this_dz
+            end if
 
          else if (CCTK_Equals(symmetry,'quadrant') == 1) then
 
-            iflag = iflag +1
             print *,"FIXME"
 
          else if (CCTK_Equals(symmetry,'bitant') == 1) then
 
-            iflag = iflag +1
             print *,"FIXME"
 
          else if (CCTK_Equals(symmetry,'full') == 1) then
 
-            iflag = iflag +1
-
 c           Set minimum values of coordinates
             x_origin = xmin
             y_origin = ymin
@@ -140,34 +146,51 @@ c        dx, dy, dz on the grid we are on
 
          if (CCTK_Equals(symmetry,'bitant') == 1) then 
 
-            iflag = iflag + 1
-            x_origin = (0.5 - cctk_gsh(1)/2)*this_dx
-            y_origin = (0.5 - cctk_gsh(2)/2)*this_dy
-            z_origin = (-dble(cctk_nghostzones(3))+0.5d0)*this_dz
+            if (no_origin==1) then
+               x_origin = (0.5 - cctk_gsh(1)/2)*this_dx
+               y_origin = (0.5 - cctk_gsh(2)/2)*this_dy
+               z_origin = (-dble(cctk_nghostzones(3))+0.5d0)*this_dz
+            else
+               x_origin = (- cctk_gsh(1)/2)*this_dx
+               y_origin = (- cctk_gsh(2)/2)*this_dy
+               z_origin = (-dble(cctk_nghostzones(3)))*this_dz
+            end if
 
          else if (CCTK_Equals(symmetry,'quadrant') == 1) then 
 
-            iflag = iflag + 1
+            if (no_origin==1) then
+               x_origin = (-dble(cctk_nghostzones(1))+0.5d0)*this_dx
+               y_origin = (-dble(cctk_nghostzones(2))+0.5d0)*this_dy
+               z_origin = (0.5D0 - cctk_gsh(3)/2)*this_dz
+            else
+               x_origin = (-dble(cctk_nghostzones(1)))*this_dx
+               y_origin = (-dble(cctk_nghostzones(2)))*this_dy
+               z_origin = (- cctk_gsh(3)/2)*this_dz               
+	    end if
 
-            x_origin = (-dble(cctk_nghostzones(1))+0.5d0)*this_dx
-            y_origin = (-dble(cctk_nghostzones(2))+0.5d0)*this_dy
-            z_origin = (0.5D0 - cctk_gsh(3)/2)*this_dz
-	    
          else if (CCTK_Equals(symmetry,'octant') == 1) then 
          
-            iflag = iflag + 1
-
-            x_origin = (-dble(cctk_nghostzones(1))+0.5d0)*this_dx
-            y_origin = (-dble(cctk_nghostzones(2))+0.5d0)*this_dy
-            z_origin = (-dble(cctk_nghostzones(3))+0.5d0)*this_dz
+            if (no_origin==1) then
+               x_origin = (-dble(cctk_nghostzones(1))+0.5d0)*this_dx
+               y_origin = (-dble(cctk_nghostzones(2))+0.5d0)*this_dy
+               z_origin = (-dble(cctk_nghostzones(3))+0.5d0)*this_dz
+            else
+               x_origin = (-dble(cctk_nghostzones(1)))*this_dx
+               y_origin = (-dble(cctk_nghostzones(2)))*this_dy
+               z_origin = (-dble(cctk_nghostzones(3)))*this_dz
+            end if
 
          else if (CCTK_Equals(symmetry,'full')==1) then 
 
-            iflag = iflag + 1
-
-            x_origin = (0.5 - cctk_gsh(1)/2)*this_dx
-            y_origin = (0.5 - cctk_gsh(2)/2)*this_dy
-            z_origin = (0.5 - cctk_gsh(3)/2)*this_dz
+            if (no_origin==1) then
+               x_origin = (0.5 - cctk_gsh(1)/2)*this_dx
+               y_origin = (0.5 - cctk_gsh(2)/2)*this_dy
+               z_origin = (0.5 - cctk_gsh(3)/2)*this_dz
+            else
+               x_origin = (- cctk_gsh(1)/2)*this_dx
+               y_origin = (- cctk_gsh(2)/2)*this_dy
+               z_origin = (- cctk_gsh(3)/2)*this_dz
+            end if
 
          end if
 
@@ -182,8 +205,6 @@ c     --------------------------------------------------------------
 
       elseif (CCTK_Equals(type,'box') == 1) then 
 
-         iflag = iflag + 1
- 
 c        Coordinates are all -0.5 to 0.5
          x_origin = -0.5
          y_origin = -0.5
@@ -212,13 +233,6 @@ c        Special cases
       end if
 
 
-c     No grid was set up
-c     ------------------
-      if (iflag.ne.1) then
-        call CCTK_WARN(0,"No grid set up in CartGrid3D")
-      end if
-
-
 c     Set spatial coordinates
 c     -----------------------
       do i=1,cctk_lsh(1)
diff --git a/src/GHExtension.c b/src/GHExtension.c
new file mode 100644
index 0000000..5177424
--- /dev/null
+++ b/src/GHExtension.c
@@ -0,0 +1,68 @@
+
+#include <stdlib.h>
+
+#include "cctk.h"
+#include "flesh.h"
+#include "Symmetry.h"
+#include "Groups.h"
+#include "Comm.h"
+#include "GHExtensions.h"
+
+
+void *Symmetry_AllocGHex(tFleshConfig *config, int convlevel, cGH *GH) {
+  
+  int gf,grid_dim,NumVars;     /* Number of  dimensions, grid functions */
+  SymmetryGHex *newGHex;  /* Type of GHextension is EinsteinBoundGHex */
+
+  printf("Setting up GH extension\n");
+  NumVars  = CCTK_GetNumVars(); /* Get number of grid functions */
+  grid_dim = CCTK_GetMaxDim();  /* Get maximal dimension of the grid */
+
+  /* allocate the GHextension */
+  newGHex = (SymmetryGHex*)malloc(sizeof(SymmetryGHex));
+  
+  /* allocation for the number of grid functions*/
+  newGHex->GFSym = (int **)malloc(NumVars*sizeof(int *));
+
+  /* allocation for the number of dimensions*/
+  for (gf=0;gf<NumVars;gf++) {
+    newGHex->GFSym[gf] = (int *)malloc(grid_dim*sizeof(int));
+  }
+
+  /* Now we have something, that looks like [0..NumVars-1][0..grid_dim-1] 
+     and we return that. For the progammer (that's me): This will be merged into
+     the GH and can be referenced  in the following manner:
+     int handle  = CCTK_GetGHExtensionHandle("Symmetry");
+                   ..... which returns a pointer the GHextension
+     BoundGHEx   = ((pGH *)GH->extensions[handle]);
+                   ..... BoundGHex can now be used as:
+     BoundGHex->GFSym[3][2] = 1 ;
+  */ 
+
+  return newGHex;  
+
+}
+  
+void Symmetry_InitGHex(cGH *GH) {
+  SymmetryGHex *newGHex;   
+  int handle;              
+  int gf,d;
+  int NumVars =CCTK_GetNumVars(); 
+  int grid_dim;                    
+
+  grid_dim = CCTK_GetMaxDim();    
+  handle   = CCTK_GetGHExtensionHandle("Symmetry"); 
+  newGHex  = (SymmetryGHex*) GH->extensions[handle]; 
+
+  /* ... and initialize them: */
+  for (gf=0;gf<NumVars;gf++) {
+    for(d=0;d<grid_dim;d++) {
+      newGHex->GFSym[gf][d] = GFSYM_UNSET;  /* not set */
+    }
+  }
+}
+      
+      
+      
+
+
diff --git a/src/ParamCheck.F b/src/ParamCheck.F
index 9495a90..4fbbc7b 100644
--- a/src/ParamCheck.F
+++ b/src/ParamCheck.F
@@ -19,20 +19,47 @@
       DECLARE_CCTK_FARGUMENTS
       DECLARE_PARAMETERS
 
-      integer :: CCTK_Equals
+      integer :: CCTK_Equals,iflag=0
 
-      if (CCTK_Equals(type,"box")==1 .and.
-     &     CCTK_Equals(symmetry,"full")==0) then
+      if (CCTK_Equals(type,'byrange') == 1) then
 
-         write(*,*)
-         ! CHAR(34) is a speechmark
-         write(*,*) "No symmetries can be used with grid = "//
-     &        CHAR(34)//"box"//CHAR(34)
-         write(*,*) "In par file set symmetry = "//CHAR(34)//"full"//CHAR(34)
+         if (CCTK_Equals(symmetry,'octant') == 1) then
+            iflag = iflag +1
+         else if (CCTK_Equals(symmetry,'quadrant') == 1) then
+            iflag = iflag +1
+         else if (CCTK_Equals(symmetry,'bitant') == 1) then
+            iflag = iflag +1
+         else if (CCTK_Equals(symmetry,'full') == 1) then
+            iflag = iflag +1
+         end if
 
-      end if 
+      else if (CCTK_Equals(type,'byspacing') == 1) then
+
+         if (CCTK_Equals(symmetry,'bitant') == 1) then 
+            iflag = iflag + 1
+         else if (CCTK_Equals(symmetry,'quadrant') == 1) then 
+            iflag = iflag + 1
+         else if (CCTK_Equals(symmetry,'octant') == 1) then 
+            iflag = iflag + 1
+         else if (CCTK_Equals(symmetry,'full')==1) then 
+            iflag = iflag + 1
+         end if
+
+      elseif (CCTK_Equals(type,'box') == 1) then 
+
+         iflag = iflag + 1
+
+         if (CCTK_Equals(symmetry,"full")==0) 
+     &      call CCTK_PARAMWARN("No symmetries can be used with box grid")
+
+      end if
+
+c     No grid was set up
+c     ------------------
+      if (iflag.ne.1) then
+        call CCTK_PARAMWARN("No grid set up in CartGrid3D")
+      end if
 
-      return
       end subroutine ParamCheck_CartGrid3D
 
 
diff --git a/src/Startup.c b/src/Startup.c
index 8b25f4d..9baebfd 100644
--- a/src/Startup.c
+++ b/src/Startup.c
@@ -1,6 +1,67 @@
+ /*@@
+   @file      Startup.c
+   @date      Mon Mar 15 15:48:42 1999
+   @author    Gerd Lanfermann
+   @desc 
+     Startup file to register the GHextension and coordinates
+   @enddesc 
+ @@*/
 
 #include "cctk.h"
+#include "flesh.h"
 #include "Coord.h"
+#include "GHExtensions.h"
+
+void *Symmetry_AllocGHex(tFleshConfig *, int, cGH *);
+int   Symmetry_InitGHex(cGH *GH);
+
+
+ /*@@
+   @routine    SymmetryStartup
+   @date       Mon Mar 15 15:49:16 1999
+   @author     Gerd Lanfermann
+   @desc 
+     Routine registers the Setup and Initialation routines for the
+     GHExtension, which holds the symmetry BCs.
+   @enddesc 
+   @calls     
+   @calledby   
+   @history 
+ 
+   @endhistory 
+
+@@*/
+
+/* Store the handle in a global variable for the moment. */
+int Symmetry_handle;
+
+int SymmetryStartup(void) {
+  
+  /* we name the GHextension "Symmetry" and get an
+     integer identifying the GHex */
+  Symmetry_handle = CCTK_RegisterGHExtension("Symmetry");
+  
+  /* Register the allocation and init routine */
+  CCTK_RegisterGHExtensionSetupGH(Symmetry_handle,Symmetry_AllocGHex);
+  CCTK_RegisterGHExtensionInitGH(Symmetry_handle,Symmetry_InitGHex);
+  return 0;
+}
+
+
+ /*@@
+   @routine    RegisterCartGrid3DCoords
+   @date       
+   @author     Gabrielle Allen
+   @desc 
+     Routine registers the coordinates provided by CartGrid3D
+   @enddesc 
+   @calls     
+   @calledby   
+   @history 
+ 
+   @endhistory 
+
+@@*/
 
 int RegisterCartGrid3DCoords()
 {
diff --git a/src/Symmetry.c b/src/Symmetry.c
new file mode 100644
index 0000000..4246559
--- /dev/null
+++ b/src/Symmetry.c
@@ -0,0 +1,238 @@
+ /*@@
+   @file      Symmetry.c
+   @date      Mon Mar 15 15:09:00 1999
+   @author    Gerd Lanfermann
+   @desc 
+     This file contains the routines for registering and applying symmetry 
+     boundary conditions
+   @enddesc 
+ @@*/
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "cctk.h"
+#include "declare_parameters.h"
+#include "flesh.h"
+#include "Symmetry.h" 
+#include "GHExtensions.h"
+#include "Groups.h"
+#include "WarnLevel.h"
+#include "Misc.h"
+#include "FortranString.h"
+
+#define DEBUG_BOUND
+
+ /*@@
+   @routine    SetSymmetry
+   @date       Mon Mar 15 15:10:58 1999
+   @author     Gerd Lanfermann
+   @desc 
+   This routine sets the GH extension (EinsteinBoundGHex *bGHex), 
+   which describes the symmetry  boundary type of each GF. Takes 
+   the name of the GF ("implementation::gfname") and the symmetry operators 
+   sx,sy,sz and inserts them in the array bGHex. 
+   These values will looked up by ApplySym
+   @enddesc 
+   @calls     
+   @calledby   
+   @history 
+ 
+   @endhistory 
+
+@@*/
+
+void SetSymmetry(cGH *GH, int sx, int sy, int sz, const char *imp_gf) {
+  
+  DECLARE_PARAMETERS
+
+  SymmetryGHex *sGHex; 
+  int index;
+
+  printf("Why am i here\n");
+  /* Pointer to the SymmetryGHextension */
+  sGHex  = (SymmetryGHex *)GH->extensions[CCTK_GetGHExtensionHandle("Symmetry")];
+
+  /* now that we have the same, get the index to the GFs */
+  index = CCTK_GetVarIndex(imp_gf);
+  if (index<0) {
+    CCTK_WARN(0,"Grid function has no index"); 
+  };
+  
+  /* Reference the hash table in the GHex and tell it what kind of
+     symmetry is being applied 
+     (depending on sym and the grid layout) 
+     If there is no symmetry necessary,set ESYM_NOSYM
+     When we apply a symmetry and find ESYM_UNSET, something went wrong! 
+   */
+
+  if (CCTK_Equals(symmetry,"full")) {
+
+#ifdef DEBUG_BOUND
+    printf(" Registered full grid symmetries for -%s- in SetSymmetry\n",imp_gf);
+#endif
+
+    sGHex->GFSym[index][0] = GFSYM_NOSYM;
+    sGHex->GFSym[index][1] = GFSYM_NOSYM;
+    sGHex->GFSym[index][2] = GFSYM_NOSYM;
+
+  } else if (CCTK_Equals(symmetry,"octant")) {
+
+#ifdef DEBUG_BOUND
+    printf(" Registered octant symmetries for -%s- in SetSymmetry\n",imp_gf);
+#endif
+
+    sGHex->GFSym[index][0] = sx;
+    sGHex->GFSym[index][1] = sy;
+    sGHex->GFSym[index][2] = sz;
+
+  } else if (CCTK_Equals(symmetry,"quadrant")) {
+
+#ifdef DEBUG_BOUND
+    printf("Registered quadrant symmetries for -%s- in SetSymmetry\n",imp_gf);
+#endif    
+
+    sGHex->GFSym[index][0] = sx;
+    sGHex->GFSym[index][1] = sy;
+    sGHex->GFSym[index][2] = GFSYM_NOSYM;
+
+  } else if (CCTK_Equals(symmetry,"bitant")) {
+
+#ifdef DEBUG_BOUND
+    printf("Registered bitant symmetries for -%s- in SetSymmetry\n",imp_gf);
+#endif    
+
+    sGHex->GFSym[index][2] = sz;
+    sGHex->GFSym[index][0] = GFSYM_NOSYM;
+    sGHex->GFSym[index][1] = GFSYM_NOSYM;
+  }
+
+  /* All untouched GFSym[][] will hold GFSYM_UNSET */
+
+}
+
+void FMODIFIER FORTRAN_NAME(SetSymmetry)(cGH *GH,  int *sx, int *sy, int *sz, ONE_FORTSTRING_ARG) {
+
+  ONE_FORTSTRING_CREATE(imp_gf) 
+
+  SetSymmetry(GH, *sx, *sy, *sz, imp_gf);
+
+  free(imp_gf);
+} 
+
+
+
+
+ /*@@
+   @routine    ApplySymmetry
+   @date       Mon Mar 15 15:16:28 1999
+   @author     Gerd Lanfermann
+   @desc 
+      Routine applies the symmetry BC to the GF is a  group as set by SetSym 
+      in GHExtension.  It is called by C or Fortran (via a wrapper) by 
+      passing the group name. The assignment of the symmetries is carried out
+      by the F routine FortranSym
+   @enddesc 
+   @calls   FortranSym  
+   @calledby   
+   @history 
+ 
+   @endhistory 
+
+@@*/
+
+void ApplySymmetry(cGH *GH, char *imp_group) {
+
+  void FORTRAN_NAME(SymmetryCondition)(int *, CCTK_REAL *, int *, int *, int *);
+  
+  DECLARE_PARAMETERS
+
+  SymmetryGHex *sGHex; 
+  int groupnum;        
+  int first,last,index,j;
+  int doSym[3];
+
+  /* Get out if we are sure no symmetries should be applied */
+  if (CCTK_Equals(symmetry,"full")) return;
+
+  /* Get the pointer to the Symmetry GH extension */
+  sGHex  = (SymmetryGHex*)GH->extensions[CCTK_GetGHExtensionHandle("Symmetry")];
+
+#ifdef DEBUG_BOUND
+  printf("\n In ApplySymmetry\n -----------\n");
+  printf(" Applying boundary conditions to -%s-\n",imp_group);
+#endif
+
+  /* Get the group number */
+  groupnum = CCTK_GetGroupIndex(imp_group);
+  if (groupnum < 0) 
+  {
+    char *message=NULL;
+    message = (char *)malloc(300*sizeof(char)+sizeof(imp_group));
+    sprintf(message,"Invalid group number decomposing -%s",imp_group);
+    CCTK_WARN(0,message);
+    free(message);
+  }
+
+  /*get the index of the first GF in the group and how many Vars there are*/
+  first = CCTK_GetFirstVarIndex_ByIndex(groupnum);
+  last  = first+CCTK_GetNumVarsInGroup_ByIndex(groupnum)-1;
+
+  /* loop over the variables in the group */
+  for (index=first; index<=last; index++) {
+
+    /* and check that we actually have a grid function (and not a scalar)*/
+    if (CCTK_GetVarGType(index) == GROUP_GF) {
+
+      /*at this point, there should be NO ESYM_UNSET anymore 
+        if there is, we forgot to register the symmetries for a GF */
+      if ((sGHex->GFSym[index][0]==GFSYM_UNSET)||
+	  (sGHex->GFSym[index][1]==GFSYM_UNSET)||
+	  (sGHex->GFSym[index][2]==GFSYM_UNSET)) {
+	char *message=NULL;
+	message = (char *)malloc(300*sizeof(char)+sizeof(imp_group));
+	sprintf(message,"Cannot apply symmetry to -%s- without registered symmetries",imp_group);
+	CCTK_WARN(1,message);
+	free(message);
+      }
+      
+      /* whether we want to apply sym depends on several things: */
+      for (j=0;j<3;j++) 
+	if ((GH->cctk_lsh[j]>1) && 
+	    (sGHex->GFSym[index][j] != GFSYM_UNSET) &&
+	    (sGHex->GFSym[index][j] != GFSYM_NOSYM))
+	  doSym[j] = 1;
+	else 
+	  doSym[j] = 0;
+	
+
+      /* Call the Fortran Symmetry Routine */
+      FORTRAN_NAME(SymmetryCondition)(
+	     GH->cctk_lsh,            
+	     /* xyz-size of PE local grid */
+	     GH->data[index][0],         
+	     /* pointer to start of data array for GF[index]*/
+	     GH->cctk_nghostzones,            
+	     /* number of ghost zones */
+	     sGHex->GFSym[index],  
+	     /* the symmetries for this GF */
+	     doSym
+	     /* flags whether to apply syms */
+	     );                       
+    }
+  }
+}
+
+
+void FMODIFIER FORTRAN_NAME(ApplySymmetry)(cGH *GH, ONE_FORTSTRING_ARG) { 
+
+  ONE_FORTSTRING_CREATE(imp_group)
+  
+  ApplySymmetry(GH,imp_group);
+
+  free(imp_group);
+}
+
+
+
+
diff --git a/src/Symmetry.h b/src/Symmetry.h
new file mode 100644
index 0000000..6c7eadc
--- /dev/null
+++ b/src/Symmetry.h
@@ -0,0 +1,32 @@
+/*@@
+   @header    Symmetry.h
+   @date      Sun 7th Mar 1999
+   @author    Gerd Lanfermann
+   @desc 
+   The extensions to the GH structure for 3D grid symmetry Treatment
+   We'll have six int array for every GF, which holds a flag for which symmetry or 
+   (physical) bnd-condition to apply at the grid faces.
+
+   * These tables are set by SetSymmetry(GF,int,int,int) 
+     during initialization. 
+   * Default values ?
+   * The information is used during evolution by Einstein_DoBound(GF), 
+     Einstein_DoSym(GF)
+
+   @endhistory
+   @version 
+ @@*/
+
+
+#define GFSYM_UNSET -42
+#define GFSYM_NOSYM -41
+
+typedef struct Symmetry {
+
+  /* Symmetry[0..GF-1][0..dim-1] */
+  /* in each direction [0,..dim-1], this will hold the symmetry 
+     operation across that plane, iff the grid layout requires this.
+     this compares to the {sx,sy,sz} of Cactus3.2  */
+  int **GFSym;
+
+} SymmetryGHex;
diff --git a/src/SymmetryCondition.F b/src/SymmetryCondition.F
new file mode 100644
index 0000000..0a53ffe
--- /dev/null
+++ b/src/SymmetryCondition.F
@@ -0,0 +1,62 @@
+
+#include "cctk.h"
+
+/*@@
+   @routine    SymmetryCondition
+   @date       Mon Mar 15 15:51:57 1999
+   @author     Gerd Lanfermann
+   @desc 
+               Routine performs the symmetry boundary operations.
+   @enddesc 
+   @calls     
+   @calledby   
+   @history 
+ 
+   @endhistory 
+@@*/
+
+
+      subroutine SymmetryCondition(nxyz,var,nghostzones,sym,doSym)
+
+      implicit none
+
+      INTEGER nxyz(3)
+      CCTK_REAL    var(nxyz(1),nxyz(2),nxyz(3))
+      INTEGER nghostzones
+      INTEGER sym(3)
+      INTEGER doSym(3)
+      
+      INTEGER sw
+      
+c      Apply symmetry if 
+c       * the grid chunk has a physical boundary (bbox)
+c       * its size in a direction is bigger than one (sh)
+c       * we actually want a symmetry (sx.ne.ESYM_UNSET)
+
+      if (doSym(1) == 1) then
+
+         do sw=1, nghostzones
+            var(sw,:,:) = sym(1)*var(nghostzones+sw,:,:)
+         end do
+
+      end if
+
+      if (doSym(2) == 1) then
+
+         do sw=1, nghostzones    
+            var(:,sw,:) = sym(2)*var(:,nghostzones+sw,:) 
+         end do
+
+      end if
+
+      if (doSym(3).eq.1) then
+
+         do sw=1, nghostzones
+            var(:,:,sw) = sym(3)*var(:,:,nghostzones+sw)
+         end do
+
+      end if
+
+      end subroutine
+
+
diff --git a/src/make.code.defn b/src/make.code.defn
index a29247e..6d823eb 100644
--- a/src/make.code.defn
+++ b/src/make.code.defn
@@ -3,8 +3,11 @@
 
 # Source files in this directory
 SRCS = CartGrid3D.F\
+       GHExtension.c\
        ParamCheck.F\
-       Startup.c
+       Startup.c\
+       Symmetry.c\
+       SymmetryCondition.F
 
 # Subdirectories containing source files
 SUBDIRS =