Make sure the current behavior in ghost cells are kept.

Author: WeiqunZhang

Tools/C_util/DiffMultiFab/diffmultifab.cpp

@@ -60,9 +60,14 @@ int main(int argc, char* argv[])
         if (ngrow > mf2.nGrow()) {
             Abort(" ngrow bigger than infile2's ngrow! ");
         }
-        if (mf1.boxArray() != mf2.boxArray()) {
-            Warning("The two multifabs have different BoxArrays");
-            AMREX_ALWAYS_ASSERT(mf1.boxArray().minimalBox() == mf2.boxArray().minimalBox());
+        bool same_boxarray = mf1.boxArray() == mf2.boxArray();
+        if (! same_boxarray) {
+            if (ParallelDescriptor::IOProcessor()) {
+                Warning("The two multifabs have different BoxArrays.");
+            }
+            AMREX_ALWAYS_ASSERT(mf1.boxArray().ixType() == mf2.boxArray().ixType() &&
+                                mf1.boxArray().contains(mf2.boxArray()) &&
+                                mf2.boxArray().contains(mf1.boxArray()));
         }
 
         const int ncomp = mf1.nComp();
@@ -79,20 +84,22 @@ int main(int argc, char* argv[])
             mf2_max[icomp] = mf2.max(icomp,ngrow);
         }
 
-        MultiFab mfdiff1(mf1.boxArray(), mf1.DistributionMap(), ncomp, ngrow);
-
-        MultiFab mfdiff(mf2.boxArray(), mf2.DistributionMap(), ncomp, ngrow);
+        MultiFab mfdiff;
+        if (same_boxarray) {
+            mfdiff.define(mf1.boxArray(), mf2.DistributionMap(), ncomp, ngrow);
 #ifdef AMREX_USE_MPI
-        {
-            MultiFab tmp(mf1.boxArray(), mf1.DistributionMap(), ncomp, ngrow);
-            MultiFab::Copy(tmp, mf1, 0, 0, ncomp, ngrow);
-            mfdiff1.Redistribute(tmp, 0, 0, ncomp, IntVect(ngrow));
-        }
+            {
+                MultiFab tmp(mf1.boxArray(), mf1.DistributionMap(), ncomp, ngrow);
+                MultiFab::Copy(tmp, mf1, 0, 0, ncomp, ngrow);
+                mfdiff.Redistribute(tmp, 0, 0, ncomp, IntVect(ngrow));
+            }
 #else
-        MultiFab::Copy(mfdiff1, mf1, 0, 0, ncomp, ngrow);
+            MultiFab::Copy(mfdiff, mf1, 0, 0, ncomp, ngrow);
 #endif
-
-        mfdiff.ParallelCopy(mfdiff1);
+        } else {
+            mfdiff.define(mf2.boxArray(), mf2.DistributionMap(), ncomp, ngrow);
+            mfdiff.ParallelCopy(mf1, 0, 0, ncomp, ngrow, ngrow);
+        }
 
         MultiFab::Subtract(mfdiff, mf2, 0, 0, ncomp, ngrow);