ENH: new broadcast version of Pstreams (#2371)

- The idea of broadcast streams is to replace multiple master to
  subProcs communications with a single MPI_Bcast.

    if (Pstream::master())
    {
        OPBstream toAll(Pstream::masterNo());
        toAll << data;
    }
    else
    {
        IPBstream fromMaster(Pstream::masterNo());
        fromMaster >> data;
    }

    // vs.
    if (Pstream::master())
    {
        for (const int proci : Pstream::subProcs())
        {
            OPstream os(Pstream::commsTypes::scheduled, proci);
            os << data;
        }
    }
    else
    {
        IPstream is(Pstream::commsTypes::scheduled, Pstream::masterNo());
        is >> data;
    }

  Can simply use UPstream::broadcast() directly for contiguous data
  with known lengths.

Based on ideas from T.Aoyagi(RIST), A.Azami(RIST)

applications/test/parallel-broadcast/Make/files

@@ -0,0 +1,3 @@
+Test-parallel-broadcast.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-parallel-broadcast

applications/test/parallel-broadcast/Make/options

@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */

applications/test/parallel-broadcast/Test-parallel-broadcast.C

@@ -0,0 +1,147 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Application
+    Test-parallel-broadcast
+
+Description
+    Test for various broadcast routines.
+
+\*---------------------------------------------------------------------------*/
+
+#include "List.H"
+#include "argList.H"
+#include "Time.H"
+#include "vector.H"
+#include "IPstream.H"
+#include "OPstream.H"
+#include "IOstreams.H"
+
+using namespace Foam;
+
+
+// This is what our new scatter will look like inside
+template<class Type>
+void testBroadcastStream
+(
+    Type& value,
+    const label comm = UPstream::worldComm
+)
+{
+    Info<< nl << "is_contiguous:" << is_contiguous<Type>::value << endl;
+    Pout<< "pre-broadcast: " << value << endl;
+
+    if (is_contiguous<Type>::value)
+    {
+         UPstream::broadcast
+         (
+             reinterpret_cast<char*>(&value),
+             sizeof(Type),
+             comm,
+             UPstream::masterNo()
+         );
+    }
+    else
+    {
+        if (UPstream::master())
+        {
+            OPBstream toAll(UPstream::masterNo(), comm);
+            toAll << value;
+        }
+        else
+        {
+            IPBstream fromMaster(UPstream::masterNo(), comm);
+            fromMaster >> value;
+        }
+    }
+
+    Pout<< "post-broadcast: " << value << endl;
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+    argList::noCheckProcessorDirectories();
+    #include "setRootCase.H"
+    #include "createTime.H"
+
+    {
+        label value = -1;
+        if (Pstream::master())
+        {
+            value = UPstream::nProcs();
+        }
+        testBroadcastStream(value);
+    }
+
+    {
+        labelList values;
+        if (Pstream::master())
+        {
+            values = identity(UPstream::nProcs());
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        wordList values;
+        if (Pstream::master())
+        {
+            values.resize(UPstream::nProcs());
+            forAll(values, i)
+            {
+                values[i] = "value_" + Foam::name(i);
+            }
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        vector values(vector::uniform(-1));
+        if (Pstream::master())
+        {
+            values = vector(1,2,3);
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        FixedList<vector, 3> values(vector::uniform(-1));
+        if (Pstream::master())
+        {
+            values = vector(1,2,3);
+        }
+        testBroadcastStream(values);
+    }
+
+    Info<< "End\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //

src/OpenFOAM/Make/files

@@ -274,6 +274,8 @@ $(Pstreams)/UIPstreamBase.C
 $(Pstreams)/UOPstreamBase.C
 $(Pstreams)/IPstreams.C
 $(Pstreams)/OPstreams.C
+$(Pstreams)/IPBstreams.C
+$(Pstreams)/OPBstreams.C
 
 dictionary = db/dictionary
 $(dictionary)/dictionary.C

src/OpenFOAM/db/IOstreams/Pstreams/IPBstreams.C

@@ -0,0 +1,107 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UIPstream.H"
+#include "IPstream.H"
+#include "IOstreams.H"
+
+// * * * * * * * * * * * * * * * * Constructor * * * * * * * * * * * * * * * //
+
+Foam::UIPBstream::UIPBstream
+(
+    const commsTypes commsType,
+    const int fromProcNo,
+    DynamicList<char>& receiveBuf,
+    label& receiveBufPosition,
+    const int tag,
+    const label comm,
+    const bool clearAtEnd,
+    IOstreamOption::streamFormat fmt
+)
+:
+    UIPstreamBase
+    (
+        commsType,
+        fromProcNo,
+        receiveBuf,
+        receiveBufPosition,
+        tag,
+        comm,
+        clearAtEnd,
+        fmt
+    )
+{
+    bufferIPCrecv();
+}
+
+
+Foam::IPBstream::IPBstream
+(
+    const commsTypes commsType,
+    const int fromProcNo,
+    const label bufSize,
+    const int tag,
+    const label comm,
+    IOstreamOption::streamFormat fmt
+)
+:
+    Pstream(commsType, bufSize),
+    UIPBstream
+    (
+        commsType,
+        fromProcNo,
+        Pstream::transferBuf_,
+        transferBufPosition_,
+        tag,
+        comm,
+        false,  // Do not clear Pstream::transferBuf_ if at end
+        fmt
+    ),
+    transferBufPosition_(0)
+{}
+
+
+Foam::IPBstream::IPBstream
+(
+    const int fromProcNo,
+    const label comm,
+    IOstreamOption::streamFormat fmt
+)
+:
+    IPBstream
+    (
+        UPstream::commsTypes::scheduled,    // irrelevant
+        fromProcNo,
+        label(0),  // bufSize
+        UPstream::msgType(),                // irrelevant
+        comm,
+        fmt
+    )
+{}
+
+
+// ************************************************************************* //

src/OpenFOAM/db/IOstreams/Pstreams/IPstream.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -31,14 +31,14 @@ Description
     Input inter-processor communications stream.
 
 SourceFiles
-    IPstream.C
+    IPstreams.C
 
 \*---------------------------------------------------------------------------*/
 
 #include "Pstream.H"
 
-#ifndef IPstream_H
+#ifndef Foam_IPstream_H
-#define IPstream_H
+#define Foam_IPstream_H
 
 #include "UIPstream.H"
 
@@ -79,6 +79,48 @@ public:
 };
 
 
+/*---------------------------------------------------------------------------*\
+                          Class IPBstream Declaration
+\*---------------------------------------------------------------------------*/
+
+//- Input inter-processor communications stream
+//- using MPI broadcast.
+class IPBstream
+:
+    public Pstream,
+    public UIPBstream
+{
+    // Private Data
+
+        //- Receive index into Pstream::transferBuf_
+        label transferBufPosition_;
+
+public:
+
+    // Constructors
+
+        //- Construct for broadcast root, optional buffer size, read format
+        IPBstream
+        (
+            const commsTypes commsType,
+            const int fromProcNo,   //!< UPstream::masterNo() - root procNo
+            const label bufSize = 0,
+            const int tag = UPstream::msgType(),
+            const label comm = UPstream::worldComm,
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+
+        //- Construct for broadcast root with optional communicator,
+        //- write format
+        explicit IPBstream
+        (
+            const int fromProcNo,   //!< UPstream::masterNo() - root procNo
+            const label comm = UPstream::worldComm,
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/OpenFOAM/db/IOstreams/Pstreams/OPBstreams.C

@@ -0,0 +1,109 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UOPstream.H"
+#include "OPstream.H"
+#include "IOstreams.H"
+
+// * * * * * * * * * * * * * * * * Constructor * * * * * * * * * * * * * * * //
+
+Foam::UOPBstream::UOPBstream
+(
+    const commsTypes commsType,
+    const int toProcNo,
+    DynamicList<char>& sendBuf,
+    const int tag,
+    const label comm,
+    const bool sendAtDestruct,
+    IOstreamOption::streamFormat fmt
+)
+:
+    UOPstreamBase(commsType, toProcNo, sendBuf, tag, comm, sendAtDestruct, fmt)
+{}
+
+
+Foam::OPBstream::OPBstream
+(
+    const commsTypes commsType,
+    const int toProcNo,
+    const label bufSize,
+    const int tag,
+    const label comm,
+    IOstreamOption::streamFormat fmt
+)
+:
+    Pstream(commsType, bufSize),
+    UOPBstream
+    (
+        commsType,
+        toProcNo,
+        Pstream::transferBuf_,
+        tag,
+        comm,
+        true,  // sendAtDestruct
+        fmt
+    )
+{}
+
+
+Foam::OPBstream::OPBstream
+(
+    const int toProcNo,
+    const label comm,
+    IOstreamOption::streamFormat fmt
+)
+:
+    OPBstream
+    (
+        UPstream::commsTypes::scheduled,    // irrelevant
+        toProcNo,
+        label(0),  // bufSize
+        UPstream::msgType(),                // irrelevant
+        comm,
+        fmt
+    )
+{}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::UOPBstream::~UOPBstream()
+{
+    if (sendAtDestruct_)
+    {
+        if (!bufferIPCsend())
+        {
+            FatalErrorInFunction
+                << "Failed broadcast message of size "
+                << sendBuf_.size() << " root: " << toProcNo_
+                << Foam::abort(FatalError);
+        }
+    }
+}
+
+
+// ************************************************************************* //

src/OpenFOAM/db/IOstreams/Pstreams/OPstream.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -31,14 +31,14 @@ Description
     Output inter-processor communications stream.
 
 SourceFiles
-    OPstream.C
+    OPstreams.C
 
 \*---------------------------------------------------------------------------*/
 
 #include "Pstream.H"
 
-#ifndef OPstream_H
+#ifndef Foam_OPstream_H
-#define OPstream_H
+#define Foam_OPstream_H
 
 #include "UOPstream.H"
 
@@ -74,6 +74,43 @@ public:
 };
 
 
+/*---------------------------------------------------------------------------*\
+                        Class OPBstream Declaration
+\*---------------------------------------------------------------------------*/
+
+//- Output inter-processor communications stream
+//- using MPI broadcast.
+class OPBstream
+:
+    public Pstream,
+    public UOPBstream
+{
+public:
+
+    // Constructors
+
+        //- Construct for broadcast root, optional buffer size, read format
+        OPBstream
+        (
+            const commsTypes commsType,
+            const int toProcNo,     //!< UPstream::masterNo() - root procNo
+            const label bufSize = 0,
+            const int tag = UPstream::msgType(),
+            const label comm = UPstream::worldComm,
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+
+        //- Construct for broadcast root with optional communicator,
+        //- write format
+        explicit OPBstream
+        (
+            const int toProcNo,     //!< UPstream::masterNo() - root procNo
+            const label comm = UPstream::worldComm,
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H

@@ -262,6 +262,68 @@ public:
 };
 
 
+/*---------------------------------------------------------------------------*\
+                         Class UIPBstream Declaration
+\*---------------------------------------------------------------------------*/
+
+//- Input inter-processor communications stream
+//- using MPI broadcast - operating on external buffer.
+class UIPBstream
+:
+    public UIPstreamBase
+{
+    // Private Member Functions
+
+        //- Initial buffer recv via broadcast, called by constructor
+        void bufferIPCrecv();
+
+
+public:
+
+    // Constructors
+
+        //- Construct given process index to read from using the given
+        //- attached receive buffer, optional communication characteristics
+        //- and IO format
+        UIPBstream
+        (
+            const commsTypes commsType,         //!< ignored
+            const int fromProcNo,               //!< UPstream::masterNo()
+            DynamicList<char>& receiveBuf,
+            label& receiveBufPosition,
+            const int tag = UPstream::msgType(),
+            const label comm = UPstream::worldComm,
+            const bool clearAtEnd = false,   // destroy receiveBuf if at end
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+
+
+    //- Destructor
+    virtual ~UIPBstream() = default;
+
+
+    // Member Functions
+
+        //- Use all read methods from base
+        using UIPstreamBase::read;
+
+
+    // Static Functions
+
+        //- Wrapped version of UPstream::broadcast
+        //  \return the message size
+        static label read
+        (
+            const commsTypes commsTypes,        //!< ignored
+            const int rootProcNo,               //!< UPstream::masterNo()
+            char* buf,
+            const std::streamsize bufSize,
+            const int tag = UPstream::msgType(),  //!< ignored
+            const label comm = UPstream::worldComm
+        );
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.H

@@ -331,6 +331,69 @@ public:
 };
 
 
+/*---------------------------------------------------------------------------*\
+                         Class UOPBstream Declaration
+\*---------------------------------------------------------------------------*/
+
+//- Output inter-processor communications stream
+//- using MPI broadcast - operating on external buffer.
+//
+// \note does not use commsType, tag etc.
+class UOPBstream
+:
+    public UOPstreamBase
+{
+    // Private Member Functions
+
+        //- Final buffer send, called by destructor
+        bool bufferIPCsend();
+
+
+public:
+
+    // Constructors
+
+        //- Construct given process index to write to using the given
+        //- attached send buffer, optional communication characteristics
+        //- and IO format
+        UOPBstream
+        (
+            const commsTypes commsType,             //!< ignored
+            const int toProcNo,                     //!< UPstream::masterNo()
+            DynamicList<char>& sendBuf,
+            const int tag = UPstream::msgType(),    //!< ignored
+            const label comm = UPstream::worldComm,
+            const bool sendAtDestruct = true,
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
+        );
+
+
+    //- Destructor, usually sends buffer on destruct.
+    virtual ~UOPBstream();
+
+
+    // Member Functions
+
+        //- Use all write methods from base
+        using UOPstreamBase::write;
+
+
+    // Static Functions
+
+        //- Wrapped version of UPstream::broadcast with const-cast
+        //  \return True on success
+        static bool write
+        (
+            const commsTypes commsType,             //!< ignored
+            const int rootProcNo,                   //!< UPstream::masterNo()
+            const char* buf,
+            const std::streamsize bufSize,
+            const int tag = UPstream::msgType(),    //!< ignored
+            const label comm = UPstream::worldComm
+        );
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/Pstream/dummy/Make/files

@@ -4,5 +4,7 @@ UPstreamReduce.C
 
 UIPstreamRead.C
 UOPstreamWrite.C
+UIPBstreamRead.C
+UOPBstreamWrite.C
 
 LIB = $(FOAM_LIBBIN)/dummy/libPstream

src/Pstream/dummy/UIPBstreamRead.C

@@ -0,0 +1,55 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UIPstream.H"
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+void Foam::UIPBstream::bufferIPCrecv()
+{
+    NotImplemented;
+}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+Foam::label Foam::UIPBstream::read
+(
+    const commsTypes commsType,
+    const int rootProcNo,
+    char* buf,
+    const std::streamsize bufSize,
+    const int tag,
+    const label communicator
+)
+{
+    NotImplemented;
+    return 0;
+}
+
+
+// ************************************************************************* //

src/Pstream/dummy/UOPBstreamWrite.C

@@ -0,0 +1,56 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UOPstream.H"
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+bool Foam::UOPBstream::bufferIPCsend()
+{
+    NotImplemented;
+    return false;
+}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+bool Foam::UOPBstream::write
+(
+    const commsTypes commsType,
+    const int rootProcNo,
+    const char* buf,
+    const std::streamsize bufSize,
+    const int tag,
+    const label communicator
+)
+{
+    NotImplemented;
+    return false;
+}
+
+
+// ************************************************************************* //

src/Pstream/mpi/Make/files

@@ -5,5 +5,7 @@ UPstreamReduce.C
 
 UIPstreamRead.C
 UOPstreamWrite.C
+UIPBstreamRead.C
+UOPBstreamWrite.C
 
 LIB = $(FOAM_MPI_LIBBIN)/libPstream

src/Pstream/mpi/UIPBstreamRead.C

@@ -0,0 +1,140 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UIPstream.H"
+#include "PstreamGlobals.H"
+#include "profilingPstream.H"
+#include "IOstreams.H"
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+void Foam::UIPBstream::bufferIPCrecv()
+{
+    // Uses double broadcast. Symmetric with UOPBstream::bufferIPCsend()
+    // 1. for the data size
+    // 2. for the data itself
+
+    // Expected message size, similar to MPI_Probe
+    // Same type must be expected in UOPBstream::bufferIPCsend()
+    label bufSize(0);
+
+    // Broadcast #1 - data size
+    if
+    (
+        !UPstream::broadcast
+        (
+            reinterpret_cast<char*>(&bufSize),
+            sizeof(label),
+            comm_,
+            fromProcNo_  //< is actually rootProcNo
+        )
+    )
+    {
+        FatalErrorInFunction
+            << "MPI_Bcast failure receiving buffer size" << nl
+            << Foam::abort(FatalError);
+    }
+
+    if (debug)
+    {
+        Pout<< "UOPBstream IPC read buffer :"
+            << " root:" << fromProcNo_
+            << " comm:" << comm_
+            << " probed size:" << bufSize
+            << " wanted size:" << recvBuf_.capacity()
+            << Foam::endl;
+    }
+
+    // No buffer size allocated/specified
+    if (!recvBuf_.capacity())
+    {
+        recvBuf_.resize(bufSize);
+    }
+
+    // This is the only real information we can trust
+    messageSize_ = bufSize;
+
+    // Broadcast #2 - data content
+    // - skip if there is no data to receive
+
+    if (messageSize_)
+    {
+        if
+        (
+            !UPstream::broadcast
+            (
+                recvBuf_.data(),
+                messageSize_,  // same as bufSize
+                comm_,
+                fromProcNo_  //< is actually rootProcNo
+            )
+        )
+        {
+            FatalErrorInFunction
+                << "MPI_Bcast failure receiving buffer data:" << bufSize << nl
+                << Foam::abort(FatalError);
+        }
+    }
+
+    // Set addressed size. Leave actual allocated memory intact.
+    recvBuf_.resize(messageSize_);
+
+    if (!messageSize_)
+    {
+        setEof();
+    }
+}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+Foam::label Foam::UIPBstream::read
+(
+    const commsTypes commsType,
+    const int rootProcNo,
+    char* buf,
+    const std::streamsize bufSize,
+    const int tag,
+    const label comm
+)
+{
+    if
+    (
+        !UPstream::broadcast(buf, bufSize, comm, rootProcNo)
+    )
+    {
+        FatalErrorInFunction
+            << "MPI_Bcast failure receiving data:" << label(bufSize) << nl
+            << Foam::abort(FatalError);
+        return 0;
+    }
+
+    return bufSize;
+}
+
+
+// ************************************************************************* //

src/Pstream/mpi/UOPBstreamWrite.C

@@ -0,0 +1,119 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "UOPstream.H"
+#include "PstreamGlobals.H"
+#include "profilingPstream.H"
+
+#include <mpi.h>
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+bool Foam::UOPBstream::bufferIPCsend()
+{
+    // Uses double broadcast
+    // 1. for the data size
+    // 2. for the data itself
+    // With this information, can determine and resize receive buffer
+
+    PstreamGlobals::checkCommunicator(comm_, toProcNo_);
+
+    // Same type must be expected in UIPBstream::bufferIPCrecv()
+    label bufSize(sendBuf_.size());
+
+    // Broadcast #1 - data size
+    if
+    (
+        !UPstream::broadcast
+        (
+            reinterpret_cast<char*>(&bufSize),
+            sizeof(label),
+            comm_,
+            toProcNo_  //< is actually rootProcNo
+        )
+    )
+    {
+        FatalErrorInFunction
+            << "MPI_Bcast failure sending buffer size:" << bufSize << nl
+            << Foam::abort(FatalError);
+        return false;
+    }
+
+    // Broadcast #2 - data content
+    // - skip if there is no data to send
+    if (bufSize)
+    {
+        if
+        (
+            !Pstream::broadcast
+            (
+                sendBuf_.data(),
+                sendBuf_.size(),  // same as bufSize
+                comm_,
+                toProcNo_  //< is actually rootProcNo
+            )
+        )
+        {
+            FatalErrorInFunction
+                << "MPI_Bcast failure sending buffer data:" << bufSize << nl
+                << Foam::abort(FatalError);
+            return false;
+        }
+    }
+
+    return true;
+}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+bool Foam::UOPBstream::write
+(
+    const commsTypes commsType,  /* unused */
+    const int rootProcNo,
+    const char* buf,
+    const std::streamsize bufSize,
+    const int tag,  /* unused */
+    const label comm
+)
+{
+    if
+    (
+        !UPstream::broadcast(const_cast<char*>(buf), bufSize, comm, rootProcNo)
+    )
+    {
+        FatalErrorInFunction
+            << "MPI_Bcast failure sending buffer data:" << label(bufSize) << nl
+            << Foam::abort(FatalError);
+        return false;
+    }
+
+    return true;
+}
+
+
+// ************************************************************************* //