ENH: reduce Offsets

io/reduced-foam-extend/src/foam/meshes/polyMesh/sliceMesh/Offsets.C

 
 #include "Offsets.H"
 
-Foam::Offsets::Offsets( label value, bool parRun ) {
-    set( value );
+void Foam::Offsets::do_reduce() {
+    label offset = 0;
+    forAll(offsets_, procI)
+    {
+        label oldOffset = offset;
+        offset += offsets_[procI];
+
+        if (offset < oldOffset)
+        {
+            FatalErrorIn("Foam::Offsets")
+                << "Overflow : sum of sizes " << offsets_
+                << " exceeds capability of label (" << labelMax
+                << "). Please recompile with larger datatype for label."
+                << exit(FatalError);
+        }
+        offsets_[procI] = offset;
+    }
+}
+
+Foam::Offsets::Offsets( label value, bool parRun, bool reduce ) {
+    set( value, reduce );
 }
 
-void Foam::Offsets::set( Foam::label value ) {
+void Foam::Offsets::set( Foam::label value, bool reduce ) {
     offsets_[ Foam::Pstream::myProcNo() ] = value;
     Foam::Pstream::gatherList( offsets_ );
     Foam::Pstream::scatterList( offsets_ );
 
+    if ( reduce ) { do_reduce(); }
+
     // If processor does not own corresponding
     // mesh entities. Problem first arised with points.
     for ( label proc = 1; proc < Foam::Pstream::nProcs(); ++proc ) {
@@ -30,3 +51,5 @@ Foam::label Foam::Offsets::upperBound( Foam::label myProcNo ) const {
 Foam::label Foam::Offsets::count( Foam::label myProcNo ) const {
     return upperBound( myProcNo ) - lowerBound( myProcNo );
 }
+
+

io/reduced-foam-extend/src/foam/meshes/polyMesh/sliceMesh/Offsets.H

@@ -8,15 +8,20 @@ namespace Foam
 
 class Offsets {
 
-    labelList offsets_{ Pstream::nProcs(), 0 };
+    labelList offsets_{ labelList(Pstream::nProcs(), 0) };
+
+    void do_reduce();
 
 public:
 
     Offsets() = default;
 
-    explicit Offsets( label value, bool parRun = Pstream::parRun() );
+    explicit Offsets( label value,
+                      bool parRun = Pstream::parRun(),
+                      bool reduce = false );
 
-    void set( label value );
+    void set( label value, 
+              bool reduce = false );
 
     label lowerBound( label ) const;
     label upperBound( label ) const;