Added epsilon shift to eliminate uneven tiebreaks

src/compute_grid_local.cpp

@@ -191,6 +191,19 @@ void ComputeGridLocal::set_grid_local()
     zfrachi = comm->mysplit[2][1];
   }
 
+  // not fully clear why this works
+  // without, sometimes get uneven assignments
+  // in case where ngridz is multiple of nprocz
+
+  double MYEPS = 1.0e-10;
+
+  xfraclo += MYEPS;
+  xfrachi += MYEPS;
+  yfraclo += MYEPS;
+  yfrachi += MYEPS;
+  zfraclo += MYEPS;
+  zfrachi += MYEPS;
+
   nxlo = static_cast<int> (xfraclo * nx);
   if (1.0*nxlo != xfraclo*nx) nxlo++;
   nxhi = static_cast<int> (xfrachi * nx);