2 files changed, 30 insertions, 2 deletions
diff --git a/Carpet/CarpetSlab/src/mapping.cc b/Carpet/CarpetSlab/src/mapping.cc
index f4b4fd351..0b5de6eae 100644
--- a/Carpet/CarpetSlab/src/mapping.cc
+++ b/Carpet/CarpetSlab/src/mapping.cc
@@ -133,9 +133,24 @@ namespace CarpetSlab {
     for (int dd=0; dd<hdim; ++dd) {
       downsample[dd] = downsample_ ? downsample_[dd] : 1;
       if (extent[dd]<0) {
+        int const oldmap = Carpet::map;
+        int const grouptype = CCTK_GroupTypeFromVarI (vindex);
+        assert (grouptype >= 0);
+        if (grouptype == CCTK_GF) {
+          assert (reflevel >= 0);
+          assert (oldmap >= 0 || maps == 1);
+          if (oldmap == -1) {
+            enter_singlemap_mode (const_cast<cGH*>(cctkGH), 0);
+          }
+        }
 	int gsh[dim];
-	int ierr = CCTK_GroupgshVI(cctkGH, dim, gsh, vindex);
+	int ierr = CCTK_GroupgshVI (cctkGH, dim, gsh, vindex);
 	assert (!ierr);
+        if (grouptype == CCTK_GF) {
+          if (oldmap == -1) {
+            leave_singlemap_mode (const_cast<cGH*>(cctkGH));
+          }
+        }
 	const int totlen = gsh[dirs[dd]-1];
 	assert (totlen>=0);
 	// Partial argument check
diff --git a/Carpet/CarpetSlab/src/slab.cc b/Carpet/CarpetSlab/src/slab.cc
index ff2ee5cfa..d50ee25a1 100644
--- a/Carpet/CarpetSlab/src/slab.cc
+++ b/Carpet/CarpetSlab/src/slab.cc
@@ -4,6 +4,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <algorithm>
 #include <vector>
 
 #include "cctk.h"
@@ -32,6 +33,7 @@ extern "C" {
 
 namespace CarpetSlab {
   
+  using namespace std;
   using namespace Carpet;
   
   
@@ -132,7 +134,7 @@ namespace CarpetSlab {
     
     // Check extent
     for (int dd=0; dd<hdim; ++dd) {
-      assert (origin[dirs[dd]-1] + length[dd] <= sizes[dirs[dd]]);
+      assert (origin[dirs[dd]-1] + length[dd] <= sizes[dirs[dd]-1]);
     }
     
     // Get insider information about variable
@@ -154,6 +156,17 @@ namespace CarpetSlab {
     // Determine own rank
     const int rank = CCTK_MyProc(cgh);
     
+    // Sanity check
+    // (if this fails, someone requested an insane number of grid points)
+    {
+      int max = INT_MAX;
+      for (int dd=0; dd<dim; ++dd) {
+        assert (length[dd] >= 0 && length[dd] <= max);
+        if (length[dd] > 0) max /= length[dd];
+      }
+      assert (typesize <= max);
+    }
+    
     // Calculate global size
     int totalsize = 1;
     for (int dd=0; dd<hdim; ++dd) {