From 310f0ea48d18866b773136aed11200b6eda6378b Mon Sep 17 00:00:00 2001
From: eschnett <>
Date: Thu, 1 Mar 2001 11:40:00 +0000
Subject: Initial revision

darcs-hash:20010301114010-f6438-12fb8a9ffcc80e86c0a97e37b5b0dae0dbc59b79.gz
---
 Carpet/CarpetSlab/src/slab.cc | 880 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 880 insertions(+)
 create mode 100644 Carpet/CarpetSlab/src/slab.cc

(limited to 'Carpet/CarpetSlab/src/slab.cc')

diff --git a/Carpet/CarpetSlab/src/slab.cc b/Carpet/CarpetSlab/src/slab.cc
new file mode 100644
index 000000000..f734aafb9
--- /dev/null
+++ b/Carpet/CarpetSlab/src/slab.cc
@@ -0,0 +1,880 @@
+// $Header: /home/eschnett/C/carpet/Carpet/Carpet/CarpetSlab/src/slab.cc,v 1.20 2004/08/19 06:35:36 schnetter Exp $
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <vector>
+
+#include "cctk.h"
+
+#include "util_Table.h"
+
+#include "bbox.hh"
+#include "bboxset.hh"
+#include "dh.hh"
+#include "gdata.hh"
+#include "gh.hh"
+#include "ggf.hh"
+#include "vect.hh"
+
+#include "carpet.hh"
+
+#include "slab.hh"
+
+extern "C" {
+  static const char* rcsid = "$Header: /home/eschnett/C/carpet/Carpet/Carpet/CarpetSlab/src/slab.cc,v 1.20 2004/08/19 06:35:36 schnetter Exp $";
+  CCTK_FILEVERSION(Carpet_CarpetSlab_slab_cc);
+}
+
+
+
+namespace CarpetSlab {
+  
+  using namespace Carpet;
+  
+  
+  
+  // Mapping object
+  // (just store the mapping)
+  struct mapping {
+    int vindex;
+    int hdim;
+    vector<int> origin;         // [vdim]
+    vector<int> dirs;           // [hdim]
+    vector<int> stride;         // [hdim]
+    vector<int> length;         // [hdim]
+  };
+  
+  
+  
+  int
+  StoreMapping (mapping * const mp)
+  {
+    int const table = Util_TableCreate (UTIL_TABLE_FLAGS_DEFAULT);
+    assert (table>=0);
+    int const ierr = Util_TableSetPointer (table, mp, "mapping");
+    assert (ierr>=0);
+    return table;
+  }
+  
+  mapping *
+  RetrieveMapping (int const table)
+  {
+    CCTK_POINTER mp;
+    int const ierr = Util_TableGetPointer (table, &mp, "mapping");
+    assert (ierr>=0);
+    return (mapping *)mp;
+  }
+  
+  void
+  DeleteMapping (int const table)
+  {
+    int const ierr = Util_TableDestroy (table);
+    assert (ierr>=0);
+  }
+  
+  
+  
+  void
+  FillSlab (const cGH* const cgh,
+            const int dest_proc,
+            const int n,
+            const int ti,
+            const int hdim,
+            const int origin[/*vdim*/],
+            const int dirs[/*hdim*/],
+            const int stride[/*hdim*/],
+            const int length[/*hdim*/],
+            void* const hdata)
+  {
+    int ierr;
+    
+    // Check Cactus grid hierarchy
+    assert (cgh);
+    
+    // Check destination processor
+    assert (dest_proc>=-1 && dest_proc<CCTK_nProcs(cgh));
+    
+    // Check variable index
+    assert (n>=0 && n<CCTK_NumVars());
+    
+    // Get info about variable
+    const int group = CCTK_GroupIndexFromVarI(n);
+    assert (group>=0);
+    const int n0 = CCTK_FirstVarIndexI(group);
+    assert (n0>=0);
+    const int var = n - n0;
+    assert (var>=0);
+    
+    // Get info about group
+    cGroup gp;
+    ierr = CCTK_GroupData (group, &gp);
+    assert (! ierr);
+    assert (gp.dim<=dim);
+    assert (CCTK_QueryGroupStorageI(cgh, group));
+    const int typesize = CCTK_VarTypeSize(gp.vartype);
+    assert (typesize>0);
+    
+    if (gp.grouptype==CCTK_GF && reflevel==-1) {
+      CCTK_WARN (0, "It is not possible to use hyperslabbing for a grid function in meta mode or global mode (use singlemap mode instead)");
+    }
+    const int rl = gp.grouptype==CCTK_GF ? reflevel : 0;
+    
+    if (gp.grouptype==CCTK_GF && Carpet::map==-1 && maps>1) {
+      CCTK_WARN (0, "It is not possible to use hyperslabbing for a grid function in level mode when there are multiple maps (use singlemap mode instead, or make sure that there is only one map)");
+    }
+    const int m = gp.grouptype==CCTK_GF ? Carpet::map : 0;
+    const int oldmap = Carpet::map;
+    if (gp.grouptype==CCTK_GF  && oldmap==-1) {
+      enter_singlemap_mode(const_cast<cGH*>(cgh), m);
+    }
+    
+    // Check dimension
+    assert (hdim>=0 && hdim<=gp.dim);
+    
+    // Get more info about group
+    cGroupDynamicData gd;
+    ierr = CCTK_GroupDynamicData (cgh, group, &gd);
+    assert (! ierr);
+    const vect<int,dim> sizes = vect<int,dim>::ref(gd.gsh);
+    for (int d=0; d<dim; ++d) {
+      assert (sizes[d] >= 0);
+    }
+    
+    // Check timelevel
+    const int num_tl = gp.numtimelevels;
+    assert (ti>=0 && ti<num_tl);
+    const int tl = -ti;
+    
+    // Check origin
+    for (int d=0; d<dim; ++d) {
+      assert (origin[d]>=0 && origin[d]<=sizes[d]);
+    }
+    
+    // Check directions
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (dirs[dd]>=1 && dirs[dd]<=dim);
+    }
+    
+    // Check stride
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (stride[dd]>0);
+    }
+    
+    // Check length
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (length[dd]>=0);
+    }
+    
+    // Check extent
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (origin[dirs[dd]-1] + length[dd] <= sizes[dirs[dd]]);
+    }
+    
+    // Get insider information about variable
+    const gh<dim>* myhh;
+    const dh<dim>* mydd;
+    const ggf<dim>* myff;
+    assert (group < (int)arrdata.size());
+    myhh = arrdata.at(group).at(m).hh;
+    assert (myhh);
+    mydd = arrdata.at(group).at(m).dd;
+    assert (mydd);
+    assert (var < (int)arrdata.at(group).at(m).data.size());
+    myff = arrdata.at(group).at(m).data.at(var);
+    assert (myff);
+    
+    // Detemine collecting processor
+    const int collect_proc = dest_proc<0 ? 0 : dest_proc;
+    
+    // Determine own rank
+    const int rank = CCTK_MyProc(cgh);
+    
+    // Calculate global size
+    int totalsize = 1;
+    for (int dd=0; dd<hdim; ++dd) {
+      totalsize *= length[dd];
+    }
+    
+    // Allocate memory
+    assert (hdata);
+    if (dest_proc==-1 || rank==dest_proc) {
+      memset (hdata, 0, totalsize * typesize);
+    }
+    
+    // Get sample data
+    const gdata<dim>* mydata;
+    mydata = (*myff)(tl, rl, 0, 0);
+    
+    // Stride of data in memory
+    const vect<int,dim> str = mydata->extent().stride();
+    
+    // Stride of collected data
+    vect<int,dim> hstr = str;
+    for (int dd=0; dd<hdim; ++dd) {
+      hstr[dirs[dd]-1] *= stride[dd];
+    }
+    
+    // Lower bound of collected data
+    vect<int,dim> hlb(0);
+    for (int d=0; d<gp.dim; ++d) {
+      hlb[d] = origin[d] * str[d];
+    }
+    
+    // Upper bound of collected data
+    vect<int,dim> hub = hlb;
+    for (int dd=0; dd<hdim; ++dd) {
+      hub[dirs[dd]-1] += (length[dd]-1) * hstr[dirs[dd]-1];
+    }
+    
+    // Calculate extent to collect
+    const bbox<int,dim> hextent (hlb, hub, hstr);
+    assert (hextent.size() == totalsize);
+    
+    // Create collector data object
+    void* myhdata = rank==collect_proc ? hdata : 0;
+    gdata<dim>* const alldata = mydata->make_typed(-1);
+    alldata->allocate (hextent, collect_proc, myhdata);
+    
+    // Done with the temporary stuff
+    mydata = 0;
+    
+    for (comm_state<dim> state; !state.done(); state.step()) {
+      
+      // Loop over all components, copying data from them
+      BEGIN_LOCAL_COMPONENT_LOOP (cgh, gp.grouptype) {
+        
+        // Get data object
+        mydata = (*myff)(tl, rl, component, mglevel);
+        
+        // Calculate overlapping extents
+        const bboxset<int,dim> myextents
+          = ((mydd->boxes.at(rl).at(component).at(mglevel).sync_not
+              | mydd->boxes.at(rl).at(component).at(mglevel).interior)
+             & hextent);
+        
+        // Loop over overlapping extents
+        for (bboxset<int,dim>::const_iterator ext_iter = myextents.begin();
+             ext_iter != myextents.end();
+             ++ext_iter) {
+          
+          // Copy data
+          alldata->copy_from (state, mydata, *ext_iter);
+          
+        }
+        
+      } END_LOCAL_COMPONENT_LOOP;
+      
+    } // for step
+    
+    // Copy result to all processors
+    if (dest_proc == -1) {
+      vector<gdata<dim>*> tmpdata(CCTK_nProcs(cgh));
+      vector<comm_state<dim> > state;
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          void* myhdata = rank==proc ? hdata : 0;
+          tmpdata.at(proc) = mydata->make_typed(-1);
+          tmpdata.at(proc)->allocate (alldata->extent(), proc, myhdata);
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+        }
+      }
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+        }
+      }
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+          delete tmpdata.at(proc);
+        }
+      }
+      
+    } // Copy result
+    
+    if (gp.grouptype==CCTK_GF  && oldmap==-1) {
+      leave_singlemap_mode(const_cast<cGH*>(cgh));
+    }
+    
+    delete alldata;
+  }
+  
+  
+  
+  void *
+  GetSlab (const cGH* const cgh,
+           const int dest_proc,
+           const int n,
+           const int ti,
+           const int hdim,
+           const int origin[/*vdim*/],
+           const int dirs[/*hdim*/],
+           const int stride[/*hdim*/],
+           const int length[/*hdim*/])
+  {
+    // Check Cactus grid hierarchy
+    assert (cgh);
+    
+    // Check destination processor
+    assert (dest_proc>=-1 && dest_proc<CCTK_nProcs(cgh));
+    
+    // Check variable index
+    assert (n>=0 && n<CCTK_NumVars());
+    
+    // Get info about variable
+    const int group = CCTK_GroupIndexFromVarI(n);
+    assert (group>=0);
+    const int n0 = CCTK_FirstVarIndexI(group);
+    assert (n0>=0);
+    const int var = n - n0;
+    assert (var>=0);
+    
+    // Get info about group
+    cGroup gp;
+    CCTK_GroupData (group, &gp);
+    assert (gp.dim<=dim);
+    assert (CCTK_QueryGroupStorageI(cgh, group));
+    const int typesize = CCTK_VarTypeSize(gp.vartype);
+    assert (typesize>0);
+    
+    if (gp.grouptype==CCTK_GF && reflevel==-1) {
+      CCTK_WARN (0, "It is not possible to use hyperslabbing for a grid function in global mode (use singlemap mode instead)");
+    }
+    const int rl = gp.grouptype==CCTK_GF ? reflevel : 0;
+    
+    if (gp.grouptype==CCTK_GF && Carpet::map==-1) {
+      CCTK_WARN (0, "It is not possible to use hyperslabbing for a grid function in level mode (use singlemap mode instead)");
+    }
+    const int m = gp.grouptype==CCTK_GF ? Carpet::map : 0;
+    
+    // Check dimension
+    assert (hdim>=0 && hdim<=gp.dim);
+    
+    // Check timelevel
+    const int num_tl = gp.numtimelevels;
+    assert (ti>=0 && ti<num_tl);
+    const int tl = -ti;
+    
+    // Check origin
+//     for (int d=0; d<dim; ++d) {
+//       assert (origin[d]>=0 && origin[d]<=sizes[d]);
+//     }
+    
+    // Check directions
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (dirs[dd]>=1 && dirs[dd]<=dim);
+    }
+    
+    // Check stride
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (stride[dd]>0);
+    }
+    
+    // Check length
+    for (int dd=0; dd<hdim; ++dd) {
+      assert (length[dd]>=0);
+    }
+    
+    // Check extent
+//     for (int dd=0; dd<hdim; ++dd) {
+//       assert (origin[dirs[dd]-1] + length[dd] <= sizes[dirs[dd]]);
+//     }
+    
+    // Get insider information about variable
+    const gh<dim>* myhh;
+    const dh<dim>* mydd;
+    const ggf<dim>* myff;
+    assert (group < (int)arrdata.size());
+    myhh = arrdata.at(group).at(m).hh;
+    assert (myhh);
+    mydd = arrdata.at(group).at(m).dd;
+    assert (mydd);
+    assert (var < (int)arrdata.at(group).at(m).data.size());
+    myff = arrdata.at(group).at(m).data.at(var);
+    assert (myff);
+    
+    // Detemine collecting processor
+    const int collect_proc = dest_proc<0 ? 0 : dest_proc;
+    
+    // Determine own rank
+    const int rank = CCTK_MyProc(cgh);
+    
+    // Calculate global size
+    int totalsize = 1;
+    for (int dd=0; dd<hdim; ++dd) {
+      totalsize *= length[dd];
+    }
+    
+    // Allocate memory
+    void* hdata = 0;
+    if (dest_proc==-1 || rank==dest_proc) {
+      assert (0);
+      hdata = malloc(totalsize * typesize);
+      assert (hdata);
+      memset (hdata, 0, totalsize * typesize);
+    }
+    
+    // Get sample data
+    const gdata<dim>* mydata;
+    mydata = (*myff)(tl, rl, 0, 0);
+    
+    // Stride of data in memory
+    const vect<int,dim> str = mydata->extent().stride();
+    
+    // Stride of collected data
+    vect<int,dim> hstr = str;
+    for (int dd=0; dd<hdim; ++dd) {
+      hstr[dirs[dd]-1] *= stride[dd];
+    }
+    
+    // Lower bound of collected data
+    vect<int,dim> hlb(0);
+    for (int d=0; d<gp.dim; ++d) {
+      hlb[d] = origin[d] * str[d];
+    }
+    
+    // Upper bound of collected data
+    vect<int,dim> hub = hlb;
+    for (int dd=0; dd<hdim; ++dd) {
+      hub[dirs[dd]-1] += (length[dd]-1) * hstr[dirs[dd]-1];
+    }
+    
+    // Calculate extent to collect
+    const bbox<int,dim> hextent (hlb, hub, hstr);
+    assert (hextent.size() == totalsize);
+    
+    // Create collector data object
+    void* myhdata = rank==collect_proc ? hdata : 0;
+    gdata<dim>* const alldata = mydata->make_typed(-1);
+    alldata->allocate (hextent, collect_proc, myhdata);
+    
+    // Done with the temporary stuff
+    mydata = 0;
+    
+    for (comm_state<dim> state; !state.done(); state.step()) {
+      
+      // Loop over all components, copying data from them
+      BEGIN_LOCAL_COMPONENT_LOOP (cgh, gp.grouptype) {
+        
+        // Get data object
+        mydata = (*myff)(tl, rl, component, mglevel);
+        
+        // Calculate overlapping extents
+        const bboxset<int,dim> myextents
+          = ((mydd->boxes.at(rl).at(component).at(mglevel).sync_not
+              | mydd->boxes.at(rl).at(component).at(mglevel).interior)
+             & hextent);
+        
+        // Loop over overlapping extents
+        for (bboxset<int,dim>::const_iterator ext_iter = myextents.begin();
+             ext_iter != myextents.end();
+             ++ext_iter) {
+          
+          // Copy data
+          alldata->copy_from (state, mydata, *ext_iter);
+          
+        }
+        
+      } END_LOCAL_COMPONENT_LOOP;
+      
+    } // for step
+    
+    // Copy result to all processors
+    if (dest_proc == -1) {
+      vector<gdata<dim>*> tmpdata(CCTK_nProcs(cgh));
+      vector<comm_state<dim> > state;
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          void* myhdata = rank==proc ? hdata : 0;
+          tmpdata.at(proc) = mydata->make_typed(-1);
+          tmpdata.at(proc)->allocate (alldata->extent(), proc, myhdata);
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+        }
+      }
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+        }
+      }
+      
+      for (int proc=0; proc<CCTK_nProcs(cgh); ++proc) {
+        if (proc != collect_proc) {
+          tmpdata.at(proc)->copy_from (state.at(proc), alldata, alldata->extent());
+          delete tmpdata.at(proc);
+        }
+      }
+      
+    } // Copy result
+    
+    delete alldata;
+    
+    // Success
+    return hdata;
+  }
+  
+  
+  
+  CCTK_INT
+  CarpetSlab_Get (CCTK_POINTER_TO_CONST const cctkGH_,
+                  CCTK_INT const mapping_handle,
+                  CCTK_INT const proc,
+                  CCTK_INT const vindex,
+                  CCTK_INT const timelevel,
+                  CCTK_INT const hdatatype,
+                  CCTK_POINTER const hdata)
+  {
+    cGH const * const cctkGH = (cGH const *) cctkGH_;
+    
+    // Check arguments
+    assert (cctkGH);
+    assert (mapping_handle>=0);
+    assert (proc==-1 || proc>=0 && proc<CCTK_nProcs(cctkGH));
+    assert (vindex>=0 && vindex<CCTK_NumVars());
+    assert (timelevel>=0);
+    assert (hdatatype>=0);
+    assert (hdata);
+    
+    // Get mapping
+    const mapping * const mp = RetrieveMapping (mapping_handle);
+    assert (mp);
+    
+    // Calculate total size
+    size_t size = 1;
+    for (size_t d=0; d<(size_t)mp->hdim; ++d) {
+      size *= mp->length[d];
+    }
+    
+    // Get type size
+    size_t const sz = CCTK_VarTypeSize (hdatatype);
+    assert (sz>0);
+    
+    // Forward call
+    FillSlab (cctkGH, proc, vindex, timelevel,
+              mp->hdim,
+              &mp->origin[0], &mp->dirs[0], &mp->stride[0], &mp->length[0],
+              hdata);
+    
+    return 0;
+  }
+  
+  
+  
+  CCTK_INT
+  CarpetSlab_GetList (CCTK_POINTER_TO_CONST const cctkGH_,
+                      CCTK_INT const mapping_handle,
+                      CCTK_INT const num_arrays,
+                      CCTK_INT const * const procs,
+                      CCTK_INT const * const vindices,
+                      CCTK_INT const * const timelevels,
+                      CCTK_INT const * const hdatatypes,
+                      CCTK_POINTER const * const hdata,
+                      CCTK_INT * const retvals)
+  {
+    cGH const * const cctkGH = (cGH const *) cctkGH_;
+    
+    // Check arguments
+    assert (cctkGH);
+    assert (mapping_handle>=0);
+    assert (num_arrays>=0);
+    assert (procs);
+    assert (vindices);
+    assert (timelevels);
+    assert (hdatatypes);
+    assert (hdata);
+    assert (retvals);
+    
+    // Remember whether there were errors
+    bool everyting_okay = true;
+    
+    // Loop over all slabs
+    for (int n=0; n<num_arrays; ++n) {
+      // Forward call
+      retvals[n] = CarpetSlab_Get (cctkGH, mapping_handle, procs[n],
+                                   vindices[n], timelevels[n], hdatatypes[n],
+                                   hdata[n]);
+      everyting_okay = everyting_okay && retvals[n];
+    }
+    
+    return everyting_okay ? 0 : -1;
+  }
+  
+  
+  
+  typedef CCTK_INT
+  (* conversion_fn_ptr) (CCTK_INT const nelems,
+                         CCTK_INT const src_stride,
+                         CCTK_INT const dst_stride,
+                         CCTK_INT const src_type,
+                         CCTK_INT const dst_type,
+                         CCTK_POINTER_TO_CONST const from,
+                         CCTK_POINTER const to);
+  
+  
+  
+  CCTK_INT
+  CarpetSlab_LocalMappingByIndex (CCTK_POINTER_TO_CONST const cctkGH_,
+                                  CCTK_INT const vindex,
+                                  CCTK_INT const hdim,
+                                  CCTK_INT const * const direction,
+                                  CCTK_INT const * const origin,
+                                  CCTK_INT const * const extent,
+                                  CCTK_INT const * const downsample_,
+                                  CCTK_INT const table_handle,
+                                  conversion_fn_ptr const conversion_fn,
+                                  CCTK_INT * const hsize_local,
+                                  CCTK_INT * const hsize_global,
+                                  CCTK_INT * const hoffset_global)
+  {
+    CCTK_WARN (0, "not implemented");
+    return 0;
+  }
+  
+  
+  
+  CCTK_INT
+  CarpetSlab_GlobalMappingByIndex (CCTK_POINTER_TO_CONST const cctkGH_,
+                                   CCTK_INT const vindex,
+                                   CCTK_INT const hdim,
+                                   CCTK_INT const * const direction,
+                                   CCTK_INT const * const origin,
+                                   CCTK_INT const * const extent,
+                                   CCTK_INT const * const downsample_,
+                                   CCTK_INT const table_handle,
+                                   conversion_fn_ptr const conversion_fn,
+                                   CCTK_INT * const hsize)
+  {
+    cGH const * const cctkGH = (cGH const *) cctkGH_;
+    
+    // Check arguments
+    assert (cctkGH);
+    assert (vindex>=0 && vindex<CCTK_NumVars());
+    assert (hdim>=0 && hdim<=dim);
+    assert (direction);
+    assert (origin);
+    assert (extent);
+    // assert (downsample);
+    // assert (table_handle>=0);
+    assert (hsize);
+    
+    // Get more information
+    int const vdim = CCTK_GroupDimFromVarI (vindex);
+    assert (vdim>=0 && vdim<=dim);
+    assert (hdim<=vdim);
+    
+    // Not implemented
+    assert (! conversion_fn);
+    
+    // Allocate memory
+    mapping * mp = new mapping;
+    
+    // Calculate more convenient representation of the direction
+    vector<int> dirs(hdim);
+    for (int d=0; d<hdim; ++d) {
+      for (int dd=0; dd<vdim; ++dd) {
+	if (direction[d*vdim+dd]!=0) {
+          dirs[d] = dd+1;
+          goto found;
+	}
+      }
+      assert (0);
+    found:;
+      for (int dd=0; dd<vdim; ++dd) {
+        assert ((direction[d*vdim+dd]!=0) == (dirs[d]==dd+1));
+      }
+      for (int dd=0; dd<d; ++dd) {
+        assert (dirs[dd] != dirs[d]);
+      }
+    }
+    
+    // Calculate lengths
+    vector<CCTK_INT> downsample(hdim);
+    for (int dd=0; dd<hdim; ++dd) {
+      downsample[dd] = downsample_ ? downsample_[dd] : 1;
+      if (extent[dd]<0) {
+	int gsh[dim];
+	int ierr = CCTK_GroupgshVI(cctkGH, dim, gsh, vindex);
+	assert (!ierr);
+	const int totlen = gsh[dirs[dd]-1];
+	assert (totlen>=0);
+	// Partial argument check
+	assert (origin[dirs[dd]-1]>=0);
+	assert (origin[dirs[dd]-1]<=totlen);
+	assert (downsample[dd]>0);
+	hsize[dd] = (totlen - origin[dirs[dd]-1]) / downsample[dd];
+      } else {
+	hsize[dd] = extent[dd];
+      }
+      assert (hsize[dd]>=0);
+    }
+    
+    // Store information
+    mp->vindex = vindex;
+    mp->hdim = hdim;
+    mp->origin.resize(vdim);
+    mp->dirs  .resize(hdim);
+    mp->stride.resize(hdim);
+    mp->length.resize(hdim);
+    for (size_t d=0; d<(size_t)vdim; ++d) {
+      mp->origin[d] = origin[d];
+    }
+    for (size_t d=0; d<(size_t)hdim; ++d) {
+      mp->dirs[d]   = dirs[d];
+      mp->stride[d] = downsample[d];
+      mp->length[d] = hsize[d];
+    }
+    
+    return StoreMapping (mp);
+  }
+  
+  
+  
+  CCTK_INT
+  CarpetSlab_FreeMapping (CCTK_INT const mapping_handle)
+  {
+    // Check arguments
+    assert (mapping_handle>=0);
+    
+    // Get mapping
+    mapping * mp = RetrieveMapping (mapping_handle);
+    assert (mp);
+    
+    // Delete storage
+    DeleteMapping (mapping_handle);
+    
+    delete mp;
+    
+    return 0;
+  }
+  
+  
+  
+  int
+  Hyperslab_GetHyperslab (const cGH* const GH,
+                          const int target_proc,
+                          const int vindex,
+                          const int vtimelvl,
+                          const int hdim,
+                          const int global_startpoint [/*vdim*/],
+                          const int directions [/*vdim*/],
+                          const int lengths [/*hdim*/],
+                          const int downsample_ [/*hdim*/],
+                          void** const hdata,
+                          int hsize [/*hdim*/])
+  {
+    const int vdim = CCTK_GroupDimFromVarI(vindex);
+    assert (vdim>=1 && vdim<=dim);
+    
+    // Check some arguments
+    assert (hdim>=0 && hdim<=dim);
+    
+    // Check output arguments
+    assert (hdata);
+    assert (hsize);
+    
+    // Calculate more convenient representation of the direction
+    int dirs[dim];              // should really be dirs[hdim]
+    // The following if statement is written according to the
+    // definition of "dir".
+    if (hdim==1) {
+      // 1-dimensional hyperslab
+      int mydir = 0;
+      for (int d=0; d<vdim; ++d) {
+	if (directions[d]!=0) {
+	  mydir = d+1;
+	  break;
+	}
+      }
+      assert (mydir>0);
+      for (int d=0; d<vdim; ++d) {
+	if (d == mydir-1) {
+	  assert (directions[d]!=0);
+	} else {
+	  assert (directions[d]==0);
+	}
+      }
+      dirs[0] = mydir;
+    } else if (hdim==vdim) {
+      // vdim-dimensional hyperslab
+      for (int d=0; d<vdim; ++d) {
+	dirs[d] = d+1;
+      }
+    } else if (hdim==2) {
+      // 2-dimensional hyperslab with vdim==3
+      assert (vdim==3);
+      int mydir = 0;
+      for (int d=0; d<vdim; ++d) {
+	if (directions[d]==0) {
+	  mydir = d+1;
+	  break;
+	}
+      }
+      assert (mydir>0);
+      for (int d=0; d<vdim; ++d) {
+	if (d == mydir-1) {
+	  assert (directions[d]==0);
+	} else {
+	  assert (directions[d]!=0);
+	}
+      }
+      int dd=0;
+      for (int d=0; d<vdim; ++d) {
+	if (d != mydir-1) {
+	  dirs[dd] = d+1;
+	  ++dd;
+	}
+      }
+      assert (dd==hdim);
+    } else {
+      assert (0);
+    }
+    // Fill remaining length
+    for (int d=vdim; d<dim; ++d) {
+      dirs[d] = d+1;
+    }
+    
+    // Calculate lengths
+    vector<int> downsample(hdim);
+    for (int dd=0; dd<hdim; ++dd) {
+      if (lengths[dd]<0) {
+	int gsh[dim];
+	int ierr = CCTK_GroupgshVI(GH, dim, gsh, vindex);
+	assert (!ierr);
+	const int totlen = gsh[dirs[dd]-1];
+	assert (totlen>=0);
+	// Partial argument check
+	assert (global_startpoint[dirs[dd]-1]>=0);
+	assert (global_startpoint[dirs[dd]-1]<=totlen);
+        downsample[dd] = downsample_ ? downsample_[dd] : 1;
+	assert (downsample[dd]>0);
+	hsize[dd] = (totlen - global_startpoint[dirs[dd]-1]) / downsample[dd];
+      } else {
+	hsize[dd] = lengths[dd];
+      }
+      assert (hsize[dd]>=0);
+    }
+    
+    // Get the slab
+    *hdata = GetSlab (GH,
+		      target_proc,
+		      vindex,
+		      vtimelvl,
+		      hdim,
+		      global_startpoint,
+		      dirs,
+		      &downsample[0],
+		      hsize);
+    
+    // Return with success
+    return 1;
+  }
+  
+  
+  
+} // namespace CarpetSlab
-- 
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