CarpetIOHDF5: Introduce API to checkpoint only a subset of groups

Introduce a new API to checkpoint only a subset of group, via an
aliased function IO_SetCheckpointGroups. This can be used for
simulation spawning, i.e. off-loading certain calculations (e.g.
analysis) outside of the main simulation.

3 files changed, 50 insertions, 2 deletions

diff --git a/Carpet/CarpetIOHDF5/interface.ccl b/Carpet/CarpetIOHDF5/interface.ccl
index e14a9c143..55d092e85 100644
--- a/Carpet/CarpetIOHDF5/interface.ccl
+++ b/Carpet/CarpetIOHDF5/interface.ccl
@@ -63,6 +63,17 @@ REQUIRES FUNCTION IO_TruncateOutputFiles
 
 
 
+# Checkpoint only a restricted set of variables
+# (Set ngroups=-1 to checkpoint all variables.)
+CCTK_INT \
+FUNCTION IO_SetCheckpointGroups(CCTK_INT ARRAY IN groups, \
+                                CCTK_INT       IN ngroups)
+PROVIDES FUNCTION IO_SetCheckpointGroups \
+    WITH CarpetIOHDF5_SetCheckpointGroups \
+    LANGUAGE C
+
+
+
 # Return a pointer to an unmodifiable C string
 # which contains a unique ID for this configuration
 CCTK_POINTER_TO_CONST \
diff --git a/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.cc b/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.cc
index 12c9a68ea..c3053c332 100644
--- a/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.cc
+++ b/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.cc
@@ -229,6 +229,28 @@ void CarpetIOHDF5_TerminationCheckpoint (CCTK_ARGUMENTS)
 }
 
 
+CCTK_INT CarpetIOHDF5_SetCheckpointGroups (CCTK_INT const * const groups,
+                                           CCTK_INT const ngroups)
+{
+  if (ngroups == -1) {
+    // Checkpoint all groups
+    groups_to_checkpoint.clear();
+  } else {
+    assert (ngroups >= 0);
+    groups_to_checkpoint.resize(CCTK_NumGroups());
+    for (int n=0; n<CCTK_NumGroups(); ++n) {
+      groups_to_checkpoint.at(n) = false;
+    }
+    for (int n=0; n<ngroups; ++n) {
+      groups_to_checkpoint.at(groups[n]) = true;
+    }
+  }
+  return 0;
+}
+
+vector<bool> groups_to_checkpoint;
+
+
 hid_t CCTKtoHDF5_Datatype (const cGH* const cctkGH,
                            int cctk_type, bool single_precision)
 {
@@ -938,9 +960,16 @@ static void Checkpoint (const cGH* const cctkGH, int called_from)
       }
 
       for (int group = CCTK_NumGroups () - 1; group >= 0; group--) {
+        /* skip variables which have been disabled for checkpointing */
+        if (not groups_to_checkpoint.empty() and
+            not groups_to_checkpoint.at(group))
+        {
+          continue;
+        }
         /* only dump groups which have storage assigned */
         if (CCTK_QueryGroupStorageI (cctkGH, group) <= 0 or
-          CCTK_NumVarsInGroupI(group) == 0) {
+            CCTK_NumVarsInGroupI(group) == 0)
+        {
           continue;
         }
 
diff --git a/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.hh b/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.hh
index dfa6a276e..3cff7bf3b 100644
--- a/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.hh
+++ b/Carpet/CarpetIOHDF5/src/CarpetIOHDF5.hh
@@ -247,7 +247,8 @@ namespace CarpetIOHDF5
 
   };                            // struct IOHDF5
 
-  // scheduled routines (must be declared as C according to schedule.ccl)
+  // scheduled and aliased routines (must be declared as C according
+  // to schedule.ccl)
   extern "C" {
 
     int CarpetIOHDF5_RecoverParameters (void);
@@ -261,8 +262,15 @@ namespace CarpetIOHDF5
     void CarpetIOHDF5_EvolutionCheckpoint (CCTK_ARGUMENTS);
     void CarpetIOHDF5_TerminationCheckpoint (CCTK_ARGUMENTS);
 
+    CCTK_INT CarpetIOHDF5_SetCheckpointGroups (CCTK_INT const *groups,
+                                               CCTK_INT ngroups);
+
   } // extern "C"
 
+  // Which groups should be checkpointed. If empty, all variables
+  // should be checkpointed (default).
+  extern vector<bool> groups_to_checkpoint;
+
 } // namespace CarpetIOHDF5
 
 #endif // !defined(CARPETIOHDF5_HH)