1 files changed, 75 insertions, 10 deletions

diff --git a/src/call_derivs.c b/src/call_derivs.c
index 22d6527..992e028 100644
--- a/src/call_derivs.c
+++ b/src/call_derivs.c
@@ -17,12 +17,15 @@ void DiffGv ( const CCTK_POINTER_TO_CONST cctkGH_, const CCTK_INT dir,
   DECLARE_CCTK_PARAMETERS
   DECLARE_CCTK_ARGUMENTS
 
-  CCTK_INT ni, nj, nk, gsize, loc_order;
+  CCTK_INT i, ni, nj, nk, gsize, loc_order;
   CCTK_REAL delta;
-  CCTK_INT bb[2];
+  CCTK_INT bb[2], loc_offset[2];
   int onesided[6];
-
+  CCTK_INT enforce_centered[6];
+  CCTK_INT offset[6];
+  CCTK_INT dummy[6];
   int nelements;
+
   void CCTK_FCALL CCTK_FNAME(deriv_gf_2_1)(const CCTK_REAL *var,
                                        const CCTK_INT *ni,
                                        const CCTK_INT *nj,
@@ -111,6 +114,7 @@ void DiffGv ( const CCTK_POINTER_TO_CONST cctkGH_, const CCTK_INT dir,
                                        const CCTK_INT *dir,
                                        const CCTK_INT *bb,
                                        const CCTK_INT *gsize,
+                                       const CCTK_INT *offset,
                                        const CCTK_REAL *delta,
                                        CCTK_REAL *dvar);
 
@@ -128,27 +132,88 @@ void DiffGv ( const CCTK_POINTER_TO_CONST cctkGH_, const CCTK_INT dir,
     loc_order = order;
   }
 
+  for (i=0; i<6; i++) {
+    enforce_centered[i] = 0;
+  }
+
+  if ( table_handle >=0 ) {
+    nelements = Util_TableGetIntArray ( table_handle, 6, dummy, "enforce_centered" );
+    if ( nelements == UTIL_ERROR_TABLE_NO_SUCH_KEY ) {
+    } else if ( nelements != 6) {
+      CCTK_WARN (0, "The options table has an entry \"enforce_centered\", but it does not have 6 elements");
+    } else {
+      for (i=0; i<6; i++) {
+        enforce_centered[i] = dummy[i];
+      }
+    }
+  }
+
+  for (i=0; i<6; i++) {
+    offset[i] = 0;
+  }
+  if ( table_handle >=0 ) {
+    nelements = Util_TableGetIntArray ( table_handle, 6, dummy, "offset" );
+    if ( nelements == UTIL_ERROR_TABLE_NO_SUCH_KEY ) {
+    } else if ( nelements != 6) {
+      CCTK_WARN (0, "The options table has an entry \"offset\", but it does not have 6 elements");
+    } else {
+      for (i=0; i<6; i++) {
+        offset[i] = dummy[i];
+      }
+    }
+  }
+
   SBP_determine_onesided_stencil (cctkGH, onesided);
 
   switch(dir) {
   case 0: {
     delta = CCTK_DELTA_SPACE(0);
-    bb[0] = onesided[0];
-    bb[1] = onesided[1];
+    if ( enforce_centered[0] ) {
+      bb[0] = 0;
+    } else {
+      bb[0] = onesided[0];
+    }
+    loc_offset[0] = offset[0];
+    if ( enforce_centered[1] ) {
+      bb[1] = 0;
+    } else {
+      bb[1] = onesided[1];
+    }
+    loc_offset[1] = offset[1];
     gsize = cctk_nghostzones[0];
     break;
   }
   case 1: {
     delta = CCTK_DELTA_SPACE(1);
-    bb[0] = onesided[2];
-    bb[1] = onesided[3];
+    if ( enforce_centered[2] ) {
+      bb[0] = 0;
+    } else {
+      bb[0] = onesided[2];
+    }
+    loc_offset[0] = offset[2];
+    if ( enforce_centered[3] ) {
+      bb[0] = 0;
+    } else {
+      bb[1] = onesided[3];
+    }
+    loc_offset[1] = offset[3];
     gsize = cctk_nghostzones[1];
     break;
   }
   case 2: {
     delta = CCTK_DELTA_SPACE(2);
-    bb[0] = onesided[4];
-    bb[1] = onesided[5];
+    if ( enforce_centered[4] ) {
+      bb[0] = 0;
+    } else {
+      bb[0] = onesided[4];
+    }
+    loc_offset[0] = offset[4];
+    if ( enforce_centered[5] ) {
+      bb[0] = 0;
+    } else {
+      bb[1] = onesided[5];
+    }
+    loc_offset[1] = offset[5];
     gsize = cctk_nghostzones[2];
     break;
   }
@@ -193,7 +258,7 @@ void DiffGv ( const CCTK_POINTER_TO_CONST cctkGH_, const CCTK_INT dir,
         break;
       }
       case 8: {
-        CCTK_FNAME(deriv_gf_8_4_opt)(var,&ni,&nj,&nk,&dir,bb,&gsize,&delta,dvar);
+        CCTK_FNAME(deriv_gf_8_4_opt)(var,&ni,&nj,&nk,&dir,bb,&gsize,loc_offset,&delta,dvar);
         break;
       }
       default: