Support accelerator data transfer

This patch provides a function interface for accelerator (GPU) devices
to be called at certain points when Carpet traverses the schedule
tree.  This can be used to copy data between the host (CPU) and the
device (GPU) as it is needed.
---
 Carpet/Carpet/interface.ccl       |   28 ++++++++++++++++++++++++++++
 Carpet/Carpet/param.ccl           |    6 ++++++
 Carpet/Carpet/src/CallFunction.cc |   12 ++++++++++++
 Carpet/Carpet/src/Comm.cc         |    8 ++++++++
 Carpet/Carpet/src/Cycle.cc        |    4 ++++
 Carpet/Carpet/src/Evolve.cc       |    2 ++
 Carpet/Carpet/src/Initialise.cc   |    2 ++
 Carpet/Carpet/src/Requirements.cc |   34 ++++++++++++++++++++++------------
 Carpet/Carpet/src/variables.cc    |    3 +++
 Carpet/Carpet/src/variables.hh    |    3 +++
 10 files changed, 90 insertions(+), 12 deletions(-)

1 files changed, 8 insertions, 0 deletions

diff --git a/Carpet/Carpet/src/Comm.cc b/Carpet/Carpet/src/Comm.cc
index 9fa2893f3..ab6106c2b 100644
--- a/Carpet/Carpet/src/Comm.cc
+++ b/Carpet/Carpet/src/Comm.cc
@@ -214,6 +214,10 @@ namespace Carpet {
     Checkpoint ("SyncGroups");
 
     assert (groups.size() > 0);
+    
+    if (CCTK_IsFunctionAliased("Accelerator_PreSync")) {
+      Accelerator_PreSync(cctkGH, &groups.front(), groups.size());
+    }
 
     for (comm_state state; not state.done(); state.step()) {
       for (int group = 0; group < (int)groups.size(); ++group) {
@@ -232,6 +236,10 @@ namespace Carpet {
         }
       }
     }
+
+    if (CCTK_IsFunctionAliased("Accelerator_PostSync")) {
+      Accelerator_PostSync(cctkGH, &groups.front(), groups.size());
+    }
   }