diff --git a/src/dataflow.cpp b/src/dataflow.cpp
index 3e6586a..4c39290 100644
--- a/src/dataflow.cpp
+++ b/src/dataflow.cpp
@@ -115,6 +115,7 @@ isl_union_map *Dataflow::MapSpaceTimeToNeighbor(unsigned space_distance, bool sp
 {
     isl_union_map *space_to_neighbor      = MapSpaceToNeighbor(space_distance, space_is_range);
     isl_union_map *time_to_neighbor       = MapTimeToPrev(time_distance, time_is_range);
+    time_to_neighbor = isl_union_map_reverse(time_to_neighbor);
     isl_union_map *space_time_to_neighbor = isl_union_map_product(space_to_neighbor, time_to_neighbor);
     if (include_self == false) {
         isl_union_map *space_time_identity = isl_union_set_identity(GetSpaceTimeDomain());
@@ -247,7 +248,7 @@ int Dataflow::GetMacNumPerPE(int mac_per_instance)
     int mac_num = GetMacNum(mac_per_instance);
     // use GetSpaceDomain instead of pe.Getdomain() here in case some pes
     // are idle
-    int dsize = GetAverageActivePENum();
+    double dsize = GetAverageActivePENum();
     return mac_num / dsize;
 }