From 52e99137eb3063f7eab67a6a036373580d196d9c Mon Sep 17 00:00:00 2001
From: Hrvoje Jasak <h.jasak@wikki.co.uk>
Date: Sat, 8 Oct 2016 19:05:14 +0100
Subject: [PATCH] Optimised global reduce for labelList

---
 .../db/IOstreams/Pstreams/PstreamReduceOps.C  |  88 ++++++++-
 .../db/IOstreams/Pstreams/PstreamReduceOps.H  |  15 +-
 .../IOstreams/Pstreams/allReduceTemplates.C   | 173 ++----------------
 3 files changed, 106 insertions(+), 170 deletions(-)

diff --git a/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.C b/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.C
index 1ccf5ed27..08bbd77fa 100644
--- a/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.C
+++ b/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.C
@@ -250,8 +250,8 @@ void Foam::reduce
 
 void Foam::reduce
 (
-    UList<label>& Value,
-    const sumOp<UList<label> >& bop,
+    List<label>& Value,
+    const sumOp<List<label> >& bop,
     const int tag,
     const label comm
 )
@@ -264,7 +264,89 @@ void Foam::reduce
         error::printStack(Pout);
     }
 
-    allReduce(*Value.begin(), Value.size(), MPI_LABEL, MPI_SUM, bop, tag, comm);
+    // Make a copy of the Value in the send buffer so that Value can be
+    // used for receive.  HJ, 8/Oct/2016
+    labelList send(Value);
+
+    int MPISize = Value.size();
+
+    MPI_Allreduce
+    (
+        send.begin(),
+        Value.begin(),
+        MPISize,
+        MPI_LABEL,
+        MPI_SUM,
+        PstreamGlobals::MPICommunicators_[comm]
+    );
+}
+
+
+void Foam::reduce
+(
+    List<label>& Value,
+    const minOp<List<label> >& bop,
+    const int tag,
+    const label comm
+)
+{
+    if (Pstream::warnComm != -1 && comm != Pstream::warnComm)
+    {
+        Pout<< "** reducing:" << Value << " with comm:" << comm
+            << " warnComm:" << Pstream::warnComm
+            << endl;
+        error::printStack(Pout);
+    }
+
+    // Make a copy of the Value in the send buffer so that Value can be
+    // used for receive.  HJ, 8/Oct/2016
+    labelList send(Value);
+
+    int MPISize = Value.size();
+
+    MPI_Allreduce
+    (
+        send.begin(),
+        Value.begin(),
+        MPISize,
+        MPI_LABEL,
+        MPI_MIN,
+        PstreamGlobals::MPICommunicators_[comm]
+    );
+}
+
+
+void Foam::reduce
+(
+    List<label>& Value,
+    const maxOp<List<label> >& bop,
+    const int tag,
+    const label comm
+)
+{
+    if (Pstream::warnComm != -1 && comm != Pstream::warnComm)
+    {
+        Pout<< "** reducing:" << Value << " with comm:" << comm
+            << " warnComm:" << Pstream::warnComm
+            << endl;
+        error::printStack(Pout);
+    }
+
+    // Make a copy of the Value in the send buffer so that Value can be
+    // used for receive.  HJ, 8/Oct/2016
+    labelList send(Value);
+
+    int MPISize = Value.size();
+
+    MPI_Allreduce
+    (
+        send.begin(),
+        Value.begin(),
+        MPISize,
+        MPI_LABEL,
+        MPI_MAX,
+        PstreamGlobals::MPICommunicators_[comm]
+    );
 }
 
 
diff --git a/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.H b/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.H
index d81dc8487..e61a74a14 100644
--- a/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.H
+++ b/src/foam/db/IOstreams/Pstreams/PstreamReduceOps.H
@@ -239,28 +239,29 @@ void reduce
 
 
 // Insist there are specialisations for the common reductions of
-// lists of labels
+// lists of labels.  Note: template function specialisation must be the
+// exact match on argument types.  HJ, 8/Oct/2016
 
 void reduce
 (
-    UList<label>& Value,
-    const sumOp<UList<label> >& bop,
+    List<label>& Value,
+    const sumOp<List<label> >& bop,
     const int tag = Pstream::msgType(),
     const label comm = Pstream::worldComm
 );
 
 void reduce
 (
-    UList<label>& Value,
-    const minOp<UList<label> >& bop,
+    List<label>& Value,
+    const minOp<List<label> >& bop,
     const int tag = Pstream::msgType(),
     const label comm = Pstream::worldComm
 );
 
 void reduce
 (
-    UList<label>& Value,
-    const maxOp<UList<label> >& bop,
+    List<label>& Value,
+    const maxOp<List<label> >& bop,
     const int tag = Pstream::msgType(),
     const label comm = Pstream::worldComm
 );
diff --git a/src/foam/db/IOstreams/Pstreams/allReduceTemplates.C b/src/foam/db/IOstreams/Pstreams/allReduceTemplates.C
index 89a2597e9..608a26dd7 100644
--- a/src/foam/db/IOstreams/Pstreams/allReduceTemplates.C
+++ b/src/foam/db/IOstreams/Pstreams/allReduceTemplates.C
@@ -44,169 +44,22 @@ void Foam::allReduce
         return;
     }
 
-//     if (Pstream::nProcs(comm) <= Pstream::nProcsSimpleSum)
-//     {
-//         if (Pstream::master(comm))
-//         {
-//             for
-//             (
-//                 int slave = Pstream::firstSlave();
-//                 slave <= Pstream::lastSlave(comm);
-//                 slave++
-//             )
-//             {
-//                 Type value;
+    // Removed send-received loop: use Allreduce instead.
+    // HJ, 8/Oct/2016
 
-//                 if
-//                 (
-//                     MPI_Recv
-//                     (
-//                         &value,
-//                         MPICount,
-//                         MPIType,
-//                         slave,
-//                         tag,
-//                         PstreamGlobals::MPICommunicators_[comm],
-//                         MPI_STATUS_IGNORE
-//                     )
-//                 )
-//                 {
-//                     FatalErrorIn
-//                     (
-//                         "void Foam::allReduce\n"
-//                         "(\n"
-//                         "    Type&,\n"
-//                         "    int,\n"
-//                         "    MPI_Datatype,\n"
-//                         "    MPI_Op,\n"
-//                         "    const BinaryOp&,\n"
-//                         "    const int\n"
-//                         ")\n"
-//                     )   << "MPI_Recv failed"
-//                         << Foam::abort(FatalError);
-//                 }
+    Type sum;
 
-//                 Value = bop(Value, value);
-//             }
-//         }
-//         else
-//         {
-//             if
-//             (
-//                 MPI_Send
-//                 (
-//                     &Value,
-//                     MPICount,
-//                     MPIType,
-//                     Pstream::masterNo(),
-//                     tag,
-//                     PstreamGlobals::MPICommunicators_[comm]
-//                 )
-//             )
-//             {
-//                 FatalErrorIn
-//                 (
-//                     "void Foam::allReduce\n"
-//                     "(\n"
-//                     "    Type&,\n"
-//                     "    int,\n"
-//                     "    MPI_Datatype,\n"
-//                     "    MPI_Op,\n"
-//                     "    const BinaryOp&,\n"
-//                     "    const int\n"
-//                     ")\n"
-//                 )   << "MPI_Send failed"
-//                     << Foam::abort(FatalError);
-//             }
-//         }
+    MPI_Allreduce
+    (
+        &Value,
+        &sum,
+        MPICount,
+        MPIType,
+        MPIOp,
+        PstreamGlobals::MPICommunicators_[comm]
+    );
 
-
-//         if (Pstream::master(comm))
-//         {
-//             for
-//             (
-//                 int slave = Pstream::firstSlave();
-//                 slave <= Pstream::lastSlave(comm);
-//                 slave++
-//             )
-//             {
-//                 if
-//                 (
-//                     MPI_Send
-//                     (
-//                         &Value,
-//                         MPICount,
-//                         MPIType,
-//                         slave,
-//                         tag,
-//                         PstreamGlobals::MPICommunicators_[comm]
-//                     )
-//                 )
-//                 {
-//                     FatalErrorIn
-//                     (
-//                         "void Foam::allReduce\n"
-//                         "(\n"
-//                         "    Type&,\n"
-//                         "    int,\n"
-//                         "    MPI_Datatype,\n"
-//                         "    MPI_Op,\n"
-//                         "    const BinaryOp&,\n"
-//                         "    const int\n"
-//                         ")\n"
-//                     )   << "MPI_Send failed"
-//                         << Foam::abort(FatalError);
-//                 }
-//             }
-//         }
-//         else
-//         {
-//             if
-//             (
-//                 MPI_Recv
-//                 (
-//                     &Value,
-//                     MPICount,
-//                     MPIType,
-//                     Pstream::masterNo(),
-//                     tag,
-//                     PstreamGlobals::MPICommunicators_[comm],
-//                     MPI_STATUS_IGNORE
-//                 )
-//             )
-//             {
-//                 FatalErrorIn
-//                 (
-//                     "void Foam::allReduce\n"
-//                     "(\n"
-//                     "    Type&,\n"
-//                     "    int,\n"
-//                     "    MPI_Datatype,\n"
-//                     "    MPI_Op,\n"
-//                     "    const BinaryOp&,\n"
-//                     "    const int\n"
-//                     ")\n"
-//                 )   << "MPI_Recv failed"
-//                     << Foam::abort(FatalError);
-//             }
-//         }
-//     }
-//     else
-//     {
-        Type sum;
-
-        MPI_Allreduce
-        (
-            &Value,
-            &sum,
-            MPICount,
-            MPIType,
-            MPIOp,
-            PstreamGlobals::MPICommunicators_[comm]
-        );
-
-        Value = sum;
-//     }
+    Value = sum;
 }