CarpetX: CarpetX errors out when it cycles time levels if those level…

…s are not valid everywhere.

This breaks code using presync. This commit causes CarpetX to sync these grid functions
instead of erroring out.

Co-authored-by: Max Morris <[email protected]>

CarpetX/src/schedule.cxx

@@ -1515,12 +1515,30 @@ void CycleTimelevels(cGH *restrict const cctkGH) {
         }
         // All time levels (except the current) must be valid everywhere for
         // checkpointed groups
-        if (groupdata.do_checkpoint)
-          for (int tl = (ntls == 1 ? 0 : 1); tl < ntls; ++tl)
-            for (int vi = 0; vi < groupdata.numvars; ++vi)
+        bool presync_only = CCTK_EQUALS(presync_mode, "presync-only");
+        if (presync_only && groupdata.do_checkpoint) {
+          std::set<int> sync_set;
+          for (int tl = (ntls == 1 ? 0 : 1); tl < ntls; ++tl) {
+            for (int vi = 0; vi < groupdata.numvars; ++vi) {
+              sync_set.insert(gi);
+            }
+          }
+          if (!sync_set.empty()) {
+            std::vector<int> sync_vec(sync_set.begin(), sync_set.end());
+            SyncGroupsByDirI(cctkGH, sync_vec.size(), sync_vec.data(), nullptr);
+          }
+        }
+        // check that what we have is correct
+        if (groupdata.do_checkpoint) {
+          std::set<int> sync_set;
+          for (int tl = (ntls == 1 ? 0 : 1); tl < ntls; ++tl) {
+            for (int vi = 0; vi < groupdata.numvars; ++vi) {
               error_if_invalid(groupdata, vi, tl, make_valid_all(), []() {
                 return "CycleTimelevels for the state vector";
               });
+            }
+          }
+        }
       });
       for (int vi = 0; vi < groupdata0.numvars; ++vi) {
         if (ntls0 > 1)