コード例 #1
0
ファイル: md_star.cpp プロジェクト: khalid-hasanov/Elemental
const DistMatrix<T,MD,STAR>&
DistMatrix<T,MD,STAR>::operator=( const DistMatrix<T,STAR,STAR>& A )
{
#ifndef RELEASE
    CallStackEntry entry("[MD,* ] = [* ,* ]");
    this->AssertNotLocked();
    this->AssertSameGrid( A.Grid() );
#endif
    this->ResizeTo( A.Height(), A.Width() );
    if( !this->Participating() )
        return *this;

    const Int lcm = this->grid_->LCM();
    const Int colShift = this->ColShift();

    const Int width = this->Width();
    const Int localHeight = this->LocalHeight();

    const T* ABuf = A.LockedBuffer();
    const Int ALDim = A.LDim();
    T* thisBuffer = this->Buffer();
    const Int thisLDim = this->LDim();
    PARALLEL_FOR
    for( Int j=0; j<width; ++j )
    {
        T* destCol = &thisBuffer[j*thisLDim];
        const T* sourceCol = &ABuf[colShift+j*ALDim];
        for( Int iLoc=0; iLoc<localHeight; ++iLoc )
            destCol[iLoc] = sourceCol[iLoc*lcm];
    }
    return *this;
}
コード例 #2
0
ファイル: Scatter.hpp プロジェクト: YingzhouLi/Elemental
void Scatter
( const DistMatrix<T,CIRC,CIRC>& A,
        DistMatrix<T,STAR,STAR>& B )
{
    DEBUG_CSE
    AssertSameGrids( A, B );

    const Int height = A.Height();
    const Int width = A.Width();
    B.Resize( height, width );

    if( B.Participating() )
    {
        const Int pkgSize = mpi::Pad( height*width );
        vector<T> buffer;
        FastResize( buffer, pkgSize );

        // Pack            
        if( A.Participating() )
            util::InterleaveMatrix
            ( height, width,
              A.LockedBuffer(), 1, A.LDim(),
              buffer.data(),    1, height );

        // Broadcast from the process that packed
        mpi::Broadcast( buffer.data(), pkgSize, A.Root(), A.CrossComm() );

        // Unpack
        util::InterleaveMatrix
        ( height, width,
          buffer.data(), 1, height,
          B.Buffer(),    1, B.LDim() );
    }
}
コード例 #3
0
const DistMatrix<T,STAR,STAR>&
DistMatrix<T,STAR,STAR>::operator=( const DistMatrix<T,VR,STAR>& A )
{
#ifndef RELEASE
    CallStackEntry entry("[* ,* ] = [VR,* ]");
    this->AssertNotLocked();
    this->AssertSameGrid( A.Grid() );
#endif
    const elem::Grid& g = this->Grid();
    this->ResizeTo( A.Height(), A.Width() );
    if( !this->Participating() )
        return *this;

    const Int p = g.Size();
    const Int height = this->Height();
    const Int width = this->Width();
    const Int localHeightOfA = A.LocalHeight();
    const Int maxLocalHeight = MaxLength(height,p);

    const Int portionSize = mpi::Pad( maxLocalHeight*width );
    T* buffer = this->auxMemory_.Require( (p+1)*portionSize );
    T* sendBuf = &buffer[0];
    T* recvBuf = &buffer[portionSize];

    // Pack
    const Int ALDim = A.LDim();
    const T* ABuf = A.LockedBuffer();
    PARALLEL_FOR
    for( Int j=0; j<width; ++j )
        MemCopy
        ( &sendBuf[j*localHeightOfA], &ABuf[j*ALDim], localHeightOfA );

    // Communicate
    mpi::AllGather
    ( sendBuf, portionSize,
      recvBuf, portionSize, g.VRComm() );

    // Unpack
    T* thisBuf = this->Buffer();
    const Int thisLDim = this->LDim();
    const Int colAlignmentOfA = A.ColAlignment();
    OUTER_PARALLEL_FOR
    for( Int k=0; k<p; ++k )
    {
        const T* data = &recvBuf[k*portionSize];
        const Int colShift = Shift_( k, colAlignmentOfA, p );
        const Int localHeight = Length_( height, colShift, p );
        INNER_PARALLEL_FOR
        for( Int j=0; j<width; ++j )
        {
            T* destCol = &thisBuf[colShift+j*thisLDim];
            const T* sourceCol = &data[j*localHeight];
            for( Int iLoc=0; iLoc<localHeight; ++iLoc )
                destCol[iLoc*p] = sourceCol[iLoc];
        }
    }
    this->auxMemory_.Release();
    return *this;
}
コード例 #4
0
const DistMatrix<T,STAR,STAR>&
DistMatrix<T,STAR,STAR>::operator=( const DistMatrix<T,STAR,VR>& A )
{
#ifndef RELEASE
    CallStackEntry entry("[* ,* ] = [* ,VR]");
    this->AssertNotLocked();
    this->AssertSameGrid( A.Grid() );
#endif
    const elem::Grid& g = this->Grid();
    this->ResizeTo( A.Height(), A.Width() );
    if( !this->Participating() )
        return *this;

    const Int p = g.Size();
    const Int height = this->Height();
    const Int width = this->Width();
    const Int localWidthOfA = A.LocalWidth();
    const Int maxLocalWidth = MaxLength(width,p);

    const Int portionSize = mpi::Pad( height*maxLocalWidth );
    T* buffer = this->auxMemory_.Require( (p+1)*portionSize );
    T* sendBuf = &buffer[0];
    T* recvBuf = &buffer[portionSize];

    // Pack
    const Int ALDim = A.LDim();
    const T* ABuf = A.LockedBuffer();
    PARALLEL_FOR
    for( Int jLoc=0; jLoc<localWidthOfA; ++jLoc )
        MemCopy( &sendBuf[jLoc*height], &ABuf[jLoc*ALDim], height );

    // Communicate
    mpi::AllGather
    ( sendBuf, portionSize,
      recvBuf, portionSize, g.VRComm() );

    // Unpack
    T* thisBuf = this->Buffer();
    const Int thisLDim = this->LDim();
    const Int rowAlignmentOfA = A.RowAlignment();
    OUTER_PARALLEL_FOR
    for( Int k=0; k<p; ++k )
    {
        const T* data = &recvBuf[k*portionSize];
        const Int rowShift = Shift_( k, rowAlignmentOfA, p );
        const Int localWidth = Length_( width, rowShift, p );
        INNER_PARALLEL_FOR
        for( Int jLoc=0; jLoc<localWidth; ++jLoc )
            MemCopy
            ( &thisBuf[(rowShift+jLoc*p)*thisLDim], 
              &data[jLoc*height], height );
    }
    this->auxMemory_.Release();
    return *this;
}
コード例 #5
0
ファイル: AllGather.hpp プロジェクト: elemental/Elemental
void AllGather
( const DistMatrix<T,        U,           V   >& A,
        DistMatrix<T,Collect<U>(),Collect<V>()>& B )
{
    EL_DEBUG_CSE
    AssertSameGrids( A, B );

    const Int height = A.Height();
    const Int width = A.Width();
    B.SetGrid( A.Grid() );
    B.Resize( height, width );

    if( A.Participating() )
    {
        if( A.DistSize() == 1 )
        {
            Copy( A.LockedMatrix(), B.Matrix() );
        }
        else
        {
            const Int colStride = A.ColStride();
            const Int rowStride = A.RowStride();
            const Int distStride = colStride*rowStride;
            const Int maxLocalHeight = MaxLength(height,colStride);
            const Int maxLocalWidth = MaxLength(width,rowStride);
            const Int portionSize = mpi::Pad( maxLocalHeight*maxLocalWidth );
            vector<T> buf;
            FastResize( buf, (distStride+1)*portionSize );
            T* sendBuf = &buf[0];
            T* recvBuf = &buf[portionSize];

            // Pack
            util::InterleaveMatrix
            ( A.LocalHeight(), A.LocalWidth(),
              A.LockedBuffer(), 1, A.LDim(),
              sendBuf,          1, A.LocalHeight() );

            // Communicate
            mpi::AllGather
            ( sendBuf, portionSize, recvBuf, portionSize, A.DistComm() );

            // Unpack
            util::StridedUnpack
            ( height, width,
              A.ColAlign(), colStride,
              A.RowAlign(), rowStride,
              recvBuf, portionSize,
              B.Buffer(), B.LDim() );
        }
    }
    if( A.Grid().InGrid() && A.CrossComm() != mpi::COMM_SELF )
        El::Broadcast( B, A.CrossComm(), A.Root() );
}
コード例 #6
0
ファイル: SVD.hpp プロジェクト: khalid-hasanov/Elemental
inline void HermitianSVD
( UpperOrLower uplo, DistMatrix<F>& A, 
  DistMatrix<BASE(F),VR,STAR>& s, DistMatrix<F>& U, DistMatrix<F>& V )
{
#ifndef RELEASE
    CallStackEntry entry("HermitianSVD");
#endif
#ifdef HAVE_PMRRR
    typedef BASE(F) R;

    // Grab an eigenvalue decomposition of A
    HermitianEig( uplo, A, s, V );

    // Redistribute the singular values into an [MR,* ] distribution
    const Grid& grid = A.Grid();
    DistMatrix<R,MR,STAR> s_MR_STAR( grid );
    s_MR_STAR.AlignWith( V.DistData() );
    s_MR_STAR = s;

    // Set the singular values to the absolute value of the eigenvalues
    const Int numLocalVals = s.LocalHeight();
    for( Int iLoc=0; iLoc<numLocalVals; ++iLoc )
    {
        const R sigma = s.GetLocal(iLoc,0);
        s.SetLocal(iLoc,0,Abs(sigma));
    }

    // Copy V into U (flipping the sign as necessary)
    U.AlignWith( V );
    U.ResizeTo( V.Height(), V.Width() );
    const Int localHeight = V.LocalHeight();
    const Int localWidth = V.LocalWidth();
    for( Int jLoc=0; jLoc<localWidth; ++jLoc )
    {
        const R sigma = s_MR_STAR.GetLocal( jLoc, 0 );
        F* UCol = U.Buffer( 0, jLoc );
        const F* VCol = V.LockedBuffer( 0, jLoc );
        if( sigma >= 0 )
            for( Int iLoc=0; iLoc<localHeight; ++iLoc )
                UCol[iLoc] = VCol[iLoc];
        else
            for( Int iLoc=0; iLoc<localHeight; ++iLoc )
                UCol[iLoc] = -VCol[iLoc];
    }
#else
    U = A;
    MakeHermitian( uplo, U );
    SVD( U, s, V );
#endif // ifdef HAVE_PMRRR
}
コード例 #7
0
ファイル: Filter.hpp プロジェクト: YingzhouLi/Elemental
void Filter
( const DistMatrix<T,Collect<U>(),Collect<V>()>& A,
        DistMatrix<T,        U,           V   >& B )
{
    DEBUG_CSE
    AssertSameGrids( A, B );

    B.Resize( A.Height(), A.Width() );
    if( !B.Participating() )
        return;

    const Int colShift = B.ColShift();
    const Int rowShift = B.RowShift();
    util::InterleaveMatrix
    ( B.LocalHeight(), B.LocalWidth(),
      A.LockedBuffer(colShift,rowShift), B.ColStride(), B.RowStride()*A.LDim(),
      B.Buffer(),                        1,             B.LDim() );
}
コード例 #8
0
void GetMappedDiagonal
( const DistMatrix<T,U,V>& A,
        AbstractDistMatrix<S>& dPre,
        function<S(const T&)> func,
        Int offset )
{
    EL_DEBUG_CSE
    EL_DEBUG_ONLY(AssertSameGrids( A, dPre ))
    ElementalProxyCtrl ctrl;
    ctrl.colConstrain = true;
    ctrl.colAlign = A.DiagonalAlign(offset);
    ctrl.rootConstrain = true;
    ctrl.root = A.DiagonalRoot(offset);

    DistMatrixWriteProxy<S,S,DiagCol<U,V>(),DiagRow<U,V>()> dProx( dPre, ctrl );
    auto& d = dProx.Get();

    d.Resize( A.DiagonalLength(offset), 1 );
    if( d.Participating() )
    {
        const Int diagShift = d.ColShift();
        const Int iStart = diagShift + Max(-offset,0);
        const Int jStart = diagShift + Max( offset,0);

        const Int colStride = A.ColStride();
        const Int rowStride = A.RowStride();
        const Int iLocStart = (iStart-A.ColShift()) / colStride;
        const Int jLocStart = (jStart-A.RowShift()) / rowStride;
        const Int iLocStride = d.ColStride() / colStride;
        const Int jLocStride = d.ColStride() / rowStride;

        const Int localDiagLength = d.LocalHeight();
        S* dBuf = d.Buffer();
        const T* ABuf = A.LockedBuffer();
        const Int ldim = A.LDim();
        EL_PARALLEL_FOR
        for( Int k=0; k<localDiagLength; ++k )
        {
            const Int iLoc = iLocStart + k*iLocStride;
            const Int jLoc = jLocStart + k*jLocStride;
            dBuf[k] = func(ABuf[iLoc+jLoc*ldim]);
        }
    }
}
コード例 #9
0
ファイル: LLT.hpp プロジェクト: mcg1969/Elemental
inline void AddInLocalData
( const DistMatrix<F,VC,STAR>& X1, DistMatrix<F,STAR,STAR>& Z )
{
#ifndef RELEASE
    PushCallStack("internal::AddInLocalData");
#endif
    const int width = X1.Width();
    const int localHeight = X1.LocalHeight();
    const int stride = X1.Grid().Size();
    const int offset = X1.ColShift();
    for( int j=0; j<width; ++j )
    {
        F* ZColBuffer = Z.Buffer(0,j);
        const F* X1ColBuffer = X1.LockedBuffer(0,j);
        for( int iLocal=0; iLocal<localHeight; ++iLocal )
            ZColBuffer[offset+stride*iLocal] += X1ColBuffer[iLocal];
    }
#ifndef RELEASE
    PopCallStack();
#endif
}
コード例 #10
0
const DistMatrix<T,STAR,STAR>&
DistMatrix<T,STAR,STAR>::operator=( const DistMatrix<T,CIRC,CIRC>& A )
{
#ifndef RELEASE
    CallStackEntry entry("[* ,* ] = [o ,o ]");
    this->AssertNotLocked();
#endif
    const Grid& g = A.Grid();
    const Int m = A.Height(); 
    const Int n = A.Width();
    this->ResizeTo( A.Height(), A.Width() );

    if( this->Participating() )
    {
        const Int pkgSize = mpi::Pad( m*n );
        T* commBuffer = this->auxMemory_.Require( pkgSize );

        if( A.Participating() )
        {
            // Pack            
            const Int ALDim = A.LDim();
            const T* ABuf = A.LockedBuffer();
            for( Int j=0; j<n; ++j )
                for( Int i=0; i<m; ++i )
                    commBuffer[i+j*m] = ABuf[i+j*ALDim];
        }

        // Broadcast from the process that packed
        mpi::Broadcast( commBuffer, pkgSize, A.Root(), g.VCComm() );

        // Unpack
        T* buffer = this->Buffer();
        const Int ldim = this->LDim();
        for( Int j=0; j<n; ++j )
            for( Int i=0; i<m; ++i )
                buffer[i+j*ldim] = commBuffer[i+j*m];        
    }

    return *this;
}
コード例 #11
0
ファイル: dist_front.hpp プロジェクト: poulson/Clique
void AccumulateRHS( const DistMatrix<F,VC,STAR>& X, DistMatrix<F,STAR,STAR>& Z )
{
    const Int height = X.Height();
    const Int width = X.Width();
    Z.Empty();
    Zeros( Z, height, width );

    const Int localHeight = X.LocalHeight();
    const Int colShift = X.ColShift();
    const int commSize = X.Grid().Size();
    const F* XBuffer = X.LockedBuffer();
    F* ZBuffer = Z.Buffer();
    const Int XLDim = X.LDim();
    const Int ZLDim = Z.LDim();
    for( Int iLoc=0; iLoc<localHeight; ++iLoc )
    {
        const Int i = colShift + iLoc*commSize;
        for( Int j=0; j<width; ++j )
            ZBuffer[i+j*ZLDim] = XBuffer[iLoc+j*XLDim];
    }
    mpi::AllReduce( ZBuffer, ZLDim*width, mpi::SUM, X.Grid().VCComm() );
}
コード例 #12
0
ファイル: dist_front.hpp プロジェクト: poulson/Clique
void FormDiagonalBlocks
( const DistMatrix<F,VC,STAR>& L, DistMatrix<F,STAR,STAR>& D, bool conjugate )
{
    const Grid& g = L.Grid();

    const Int height = L.Width();
    const Int blocksize = Blocksize();

    const int commRank = g.VCRank();
    const int commSize = g.Size();

    const Int localHeight = Length(height,commRank,commSize);
    const Int maxLocalHeight = MaxLength(height,commSize);
    const Int portionSize = maxLocalHeight*blocksize;

    std::vector<F> sendBuffer( portionSize );
    const Int colShift = L.ColShift();
    const Int LLDim = L.LDim();
    const F* LBuffer = L.LockedBuffer();
    if( conjugate )
    {
        for( Int iLoc=0; iLoc<localHeight; ++iLoc )
        {
            const Int i = colShift + iLoc*commSize;
            const Int block = i / blocksize;
            const Int jStart = block*blocksize;
            const Int b = std::min(height-jStart,blocksize);
            for( Int jOff=0; jOff<b; ++jOff )
                sendBuffer[iLoc*blocksize+jOff] = 
                    Conj(LBuffer[iLoc+(jStart+jOff)*LLDim]);
        }
    }
    else
    {
        for( Int iLoc=0; iLoc<localHeight; ++iLoc )
        {
            const Int i = colShift + iLoc*commSize;
            const Int block = i / blocksize;
            const Int jStart = block*blocksize;
            const Int b = std::min(height-jStart,blocksize);
            for( Int jOff=0; jOff<b; ++jOff )
                sendBuffer[iLoc*blocksize+jOff] = 
                    LBuffer[iLoc+(jStart+jOff)*LLDim];
        }
    }

    std::vector<F> recvBuffer( portionSize*commSize );
    mpi::AllGather
    ( &sendBuffer[0], portionSize, &recvBuffer[0], portionSize, g.VCComm() );
    SwapClear( sendBuffer );
    
    D.Resize( blocksize, height );
    F* DBuffer = D.Buffer();
    const Int DLDim = D.LDim();
    for( Int proc=0; proc<commSize; ++proc )
    {
        const F* procRecv = &recvBuffer[proc*portionSize];
        const Int procLocalHeight = Length(height,proc,commSize);
        for( Int iLoc=0; iLoc<procLocalHeight; ++iLoc )
        {
            const Int i = proc + iLoc*commSize;
            for( Int jOff=0; jOff<blocksize; ++jOff )
                DBuffer[jOff+i*DLDim] = procRecv[jOff+iLoc*blocksize];
        }
    }
}
コード例 #13
0
void ColAllToAllPromote
( const DistMatrix<T,        U,                     V   >& A,
        DistMatrix<T,Partial<U>(),PartialUnionRow<U,V>()>& B )
{
    DEBUG_CSE
    AssertSameGrids( A, B );

    const Int height = A.Height();
    const Int width = A.Width();
    B.AlignColsAndResize
    ( Mod(A.ColAlign(),B.ColStride()), height, width, false, false );
    if( !B.Participating() )
        return;

    const Int colStride = A.ColStride();
    const Int colStridePart = A.PartialColStride();
    const Int colStrideUnion = A.PartialUnionColStride();
    const Int colRankPart = A.PartialColRank();
    const Int colDiff = B.ColAlign() - Mod(A.ColAlign(),colStridePart);

    const Int maxLocalHeight = MaxLength(height,colStride);
    const Int maxLocalWidth = MaxLength(width,colStrideUnion);
    const Int portionSize = mpi::Pad( maxLocalHeight*maxLocalWidth );

    if( colDiff == 0 )
    {
        if( A.PartialUnionColStride() == 1 )
        {
            Copy( A.LockedMatrix(), B.Matrix() );
        }
        else
        {
            vector<T> buffer;
            FastResize( buffer, 2*colStrideUnion*portionSize );
            T* firstBuf  = &buffer[0];
            T* secondBuf = &buffer[colStrideUnion*portionSize];

            // Pack            
            util::RowStridedPack
            ( A.LocalHeight(), width,
              B.RowAlign(), colStrideUnion,
              A.LockedBuffer(), A.LDim(),
              firstBuf,         portionSize );

            // Simultaneously Gather in columns and Scatter in rows
            mpi::AllToAll
            ( firstBuf,  portionSize,
              secondBuf, portionSize, A.PartialUnionColComm() );

            // Unpack
            util::PartialColStridedUnpack 
            ( height, B.LocalWidth(),
              A.ColAlign(), colStride,
              colStrideUnion, colStridePart, colRankPart,
              B.ColShift(),
              secondBuf,  portionSize,
              B.Buffer(), B.LDim() );
        }
    }
    else
    {
#ifdef EL_UNALIGNED_WARNINGS
        if( A.Grid().Rank() == 0 )
            cerr << "Unaligned PartialColAllToAllPromote" << endl;
#endif
        const Int sendColRankPart = Mod( colRankPart+colDiff, colStridePart );
        const Int recvColRankPart = Mod( colRankPart-colDiff, colStridePart );

        vector<T> buffer;
        FastResize( buffer, 2*colStrideUnion*portionSize );
        T* firstBuf  = &buffer[0];
        T* secondBuf = &buffer[colStrideUnion*portionSize];

        // Pack
        util::RowStridedPack
        ( A.LocalHeight(), width,
          B.RowAlign(), colStrideUnion,
          A.LockedBuffer(), A.LDim(),
          secondBuf,        portionSize );

        // Realign the input
        mpi::SendRecv
        ( secondBuf, colStrideUnion*portionSize, sendColRankPart,
          firstBuf,  colStrideUnion*portionSize, recvColRankPart,
          A.PartialColComm() );

        // Simultaneously Scatter in columns and Gather in rows
        mpi::AllToAll
        ( firstBuf,  portionSize,
          secondBuf, portionSize, A.PartialUnionColComm() );

        // Unpack
        util::PartialColStridedUnpack 
        ( height, B.LocalWidth(),
          A.ColAlign(), colStride,
          colStrideUnion, colStridePart, recvColRankPart,
          B.ColShift(),
          secondBuf,  portionSize,
          B.Buffer(), B.LDim() );
    }
}
コード例 #14
0
void TranslateBetweenGrids
( const DistMatrix<T,MC,MR>& A, DistMatrix<T,MC,MR>& B ) 
{
    DEBUG_ONLY(CSE cse("copy::TranslateBetweenGrids [MC,MR]"))

    B.Resize( A.Height(), A.Width() );
    // Just need to ensure that each viewing comm contains the other team's
    // owning comm. Congruence is too strong.

    // Compute the number of process rows and columns that each process
    // needs to send to.
    const Int colStride = B.ColStride();
    const Int rowStride = B.RowStride();
    const Int colRank = B.ColRank();
    const Int rowRank = B.RowRank();
    const Int colStrideA = A.ColStride();
    const Int rowStrideA = A.RowStride();
    const Int colGCD = GCD( colStride, colStrideA );
    const Int rowGCD = GCD( rowStride, rowStrideA );
    const Int colLCM = colStride*colStrideA / colGCD;
    const Int rowLCM = rowStride*rowStrideA / rowGCD;
    const Int numColSends = colStride / colGCD;
    const Int numRowSends = rowStride / rowGCD;

    const Int colAlign = B.ColAlign();
    const Int rowAlign = B.RowAlign();
    const Int colAlignA = A.ColAlign();
    const Int rowAlignA = A.RowAlign();

    const bool inBGrid = B.Participating();
    const bool inAGrid = A.Participating();
    if( !inBGrid && !inAGrid )
        return;

    const Int maxSendSize =
        (A.Height()/(colStrideA*numColSends)+1) *
        (A.Width()/(rowStrideA*numRowSends)+1);

    // Translate the ranks from A's VC communicator to B's viewing so that
    // we can match send/recv communicators. Since A's VC communicator is not
    // necessarily defined on every process, we instead work with A's owning
    // group and account for row-major ordering if necessary.
    const int sizeA = A.Grid().Size();
    vector<int> rankMap(sizeA), ranks(sizeA);
    if( A.Grid().Order() == COLUMN_MAJOR )
    {
        for( int j=0; j<sizeA; ++j )
            ranks[j] = j;
    }
    else
    {
        // The (i,j) = i + j*colStrideA rank in the column-major ordering is
        // equal to the j + i*rowStrideA rank in a row-major ordering.
        // Since we desire rankMap[i+j*colStrideA] to correspond to process
        // (i,j) in A's grid's rank in this viewing group, ranks[i+j*colStrideA]
        // should correspond to process (i,j) in A's owning group. Since the
        // owning group is ordered row-major in this case, its rank is
        // j+i*rowStrideA. Note that setting
        // ranks[j+i*rowStrideA] = i+j*colStrideA is *NOT* valid.
        for( int i=0; i<colStrideA; ++i )
            for( int j=0; j<rowStrideA; ++j )
                ranks[i+j*colStrideA] = j+i*rowStrideA;
    }
    mpi::Translate
    ( A.Grid().OwningGroup(), sizeA, &ranks[0],
      B.Grid().ViewingComm(), &rankMap[0] );

    // Have each member of A's grid individually send to all numRow x numCol
    // processes in order, while the members of this grid receive from all
    // necessary processes at each step.
    Int requiredMemory = 0;
    if( inAGrid )
        requiredMemory += maxSendSize;
    if( inBGrid )
        requiredMemory += maxSendSize;
    vector<T> auxBuf( requiredMemory );
    Int offset = 0;
    T* sendBuf = &auxBuf[offset];
    if( inAGrid )
        offset += maxSendSize;
    T* recvBuf = &auxBuf[offset];

    Int recvRow = 0; // avoid compiler warnings...
    if( inAGrid )
        recvRow = Mod(Mod(A.ColRank()-colAlignA,colStrideA)+colAlign,colStride);
    for( Int colSend=0; colSend<numColSends; ++colSend )
    {
        Int recvCol = 0; // avoid compiler warnings...
        if( inAGrid )
            recvCol=Mod(Mod(A.RowRank()-rowAlignA,rowStrideA)+rowAlign,
                        rowStride);
        for( Int rowSend=0; rowSend<numRowSends; ++rowSend )
        {
            mpi::Request sendRequest;
            // Fire off this round of non-blocking sends
            if( inAGrid )
            {
                // Pack the data
                Int sendHeight = Length(A.LocalHeight(),colSend,numColSends);
                Int sendWidth = Length(A.LocalWidth(),rowSend,numRowSends);
                copy::util::InterleaveMatrix
                ( sendHeight, sendWidth,
                  A.LockedBuffer(colSend,rowSend),
                 numColSends, numRowSends*A.LDim(),
                  sendBuf, 1, sendHeight );
                // Send data
                const Int recvVCRank = recvRow + recvCol*colStride;
                const Int recvViewingRank = B.Grid().VCToViewing( recvVCRank );
                mpi::ISend
                ( sendBuf, sendHeight*sendWidth, recvViewingRank,
                  B.Grid().ViewingComm(), sendRequest );
            }
            // Perform this round of recv's
            if( inBGrid )
            {
                const Int sendColOffset = colAlignA;
                const Int recvColOffset =
                    (colSend*colStrideA+colAlign) % colStride;
                const Int sendRowOffset = rowAlignA;
                const Int recvRowOffset =
                    (rowSend*rowStrideA+rowAlign) % rowStride;

                const Int firstSendRow =
                    Mod( Mod(colRank-recvColOffset,colStride)+sendColOffset,
                         colStrideA );
                const Int firstSendCol =
                    Mod( Mod(rowRank-recvRowOffset,rowStride)+sendRowOffset,
                         rowStrideA );

                const Int colShift = Mod( colRank-recvColOffset, colStride );
                const Int rowShift = Mod( rowRank-recvRowOffset, rowStride );
                const Int numColRecvs = Length( colStrideA, colShift, colStride );
                const Int numRowRecvs = Length( rowStrideA, rowShift, rowStride );

                // Recv data
                // For now, simply receive sequentially. Until we switch to
                // nonblocking recv's, we won't be using much of the
                // recvBuf
                Int sendRow = firstSendRow;
                for( Int colRecv=0; colRecv<numColRecvs; ++colRecv )
                {
                    const Int sendColShift = Shift( sendRow, colAlignA, colStrideA ) + colSend*colStrideA;
                    const Int sendHeight = Length( A.Height(), sendColShift, colLCM );
                    const Int localColOffset = (sendColShift-B.ColShift()) / colStride;

                    Int sendCol = firstSendCol;
                    for( Int rowRecv=0; rowRecv<numRowRecvs; ++rowRecv )
                    {
                        const Int sendRowShift = Shift( sendCol, rowAlignA, rowStrideA ) + rowSend*rowStrideA;
                        const Int sendWidth = Length( A.Width(), sendRowShift, rowLCM );
                        const Int localRowOffset = (sendRowShift-B.RowShift()) / rowStride;

                        const Int sendVCRank = sendRow+sendCol*colStrideA;
                        mpi::Recv
                        ( recvBuf, sendHeight*sendWidth, rankMap[sendVCRank],
                          B.Grid().ViewingComm() );

                        // Unpack the data
                        copy::util::InterleaveMatrix
                        ( sendHeight, sendWidth,
                          recvBuf, 1, sendHeight,
                          B.Buffer(localColOffset,localRowOffset),
                          colLCM/colStride, (rowLCM/rowStride)*B.LDim() );

                        // Set up the next send col
                        sendCol = (sendCol + rowStride) % rowStrideA;
                    }
                    // Set up the next send row
                    sendRow = (sendRow + colStride) % colStrideA;
                }
            }
            // Ensure that this round of non-blocking sends completes
            if( inAGrid )
            {
                mpi::Wait( sendRequest );
                recvCol = (recvCol + rowStrideA) % rowStride;
            }
        }
        if( inAGrid )
            recvRow = (recvRow + colStrideA) % colStride;
    }
}
コード例 #15
0
ファイル: NN.hpp プロジェクト: khalid-hasanov/Elemental
inline void
Cannon_NN
( T alpha, const DistMatrix<T>& A,
           const DistMatrix<T>& B,
  T beta,        DistMatrix<T>& C )
{
#ifndef RELEASE
    CallStackEntry entry("gemm::Cannon_NN");
    if( A.Grid() != B.Grid() || B.Grid() != C.Grid() )
        LogicError("{A,B,C} must have the same grid");
    if( A.Height() != C.Height() ||
        B.Width()  != C.Width()  ||
        A.Width()  != B.Height() )
    {
        std::ostringstream msg;
        msg << "Nonconformal matrices: \n"
            << "  A ~ " << A.Height() << " x " << A.Width() << "\n"
            << "  B ~ " << B.Height() << " x " << B.Width() << "\n"
            << "  C ~ " << C.Height() << " x " << C.Width() << "\n";
        LogicError( msg.str() );
    }
#endif
    const Grid& g = A.Grid();
    if( g.Height() != g.Width() )
        LogicError("Process grid must be square for Cannon's");
    if( C.ColAlignment() != A.ColAlignment() || 
        C.RowAlignment() != B.RowAlignment() )
        LogicError("C is not properly aligned");

    const Int row = g.Row();
    const Int col = g.Col();
    const Int pSqrt = g.Height();
    mpi::Comm rowComm = g.RowComm();
    mpi::Comm colComm = g.ColComm(); 
    if( A.Width() % pSqrt != 0 )
        LogicError("For now, width(A) must be integer multiple of sqrt(p)");

    // Begin by scaling our local portion of C
    Scale( beta, C );

    // Load the initial A and B packages (may want to transpose B...)
    const Int localHeightA = A.LocalHeight();
    const Int localHeightB = B.LocalHeight();
    const Int localWidthA = A.LocalWidth();
    const Int localWidthB = B.LocalWidth();
    Matrix<T> pkgA(localHeightA,localWidthA,localHeightA), 
              pkgB(localHeightB,localWidthB,localHeightB);
    for( Int jLoc=0; jLoc<localWidthA; ++jLoc )
        MemCopy
        ( pkgA.Buffer(0,jLoc), A.LockedBuffer(0,jLoc), localHeightA );
    for( Int jLoc=0; jLoc<localWidthB; ++jLoc )
        MemCopy
        ( pkgB.Buffer(0,jLoc), B.LockedBuffer(0,jLoc), localHeightB );

    // Perform the initial circular shifts so that our A and B packages align
    const Int rowShiftA = A.RowShift();
    const Int colShiftB = B.ColShift();
    const Int leftInitA = (col+pSqrt-colShiftB) % pSqrt;
    const Int rightInitA = (col+colShiftB) % pSqrt;
    const Int aboveInitB = (row+pSqrt-rowShiftA) % pSqrt;
    const Int belowInitB = (row+rowShiftA) % pSqrt;
    const Int pkgSizeA = localHeightA*localWidthA;
    const Int pkgSizeB = localHeightB*localWidthB;
    mpi::SendRecv( pkgA.Buffer(), pkgSizeA, leftInitA, rightInitA, rowComm );
    mpi::SendRecv( pkgB.Buffer(), pkgSizeB, aboveInitB, belowInitB, colComm );

    // Now begin the data flow
    const Int aboveRow = (row+pSqrt-1) % pSqrt;
    const Int belowRow = (row+1) % pSqrt;
    const Int leftCol = (col+pSqrt-1) % pSqrt;
    const Int rightCol = (col+1) % pSqrt;
    for( Int q=0; q<pSqrt; ++q )
    {
        Gemm( NORMAL, NORMAL, alpha, pkgA, pkgB, T(1), C.Matrix() );
        if( q != pSqrt-1 )
        {
            mpi::SendRecv
            ( pkgA.Buffer(), pkgSizeA, leftCol, rightCol, rowComm );
            mpi::SendRecv
            ( pkgB.Buffer(), pkgSizeB, aboveRow, belowRow, colComm );
        }
    }
}
コード例 #16
0
const DistMatrix<T,STAR,STAR>&
DistMatrix<T,STAR,STAR>::operator=( const DistMatrix<T,STAR,MD>& A )
{ 
#ifndef RELEASE
    CallStackEntry entry("[* ,* ] = [* ,MD]");
    this->AssertNotLocked();
    this->AssertSameGrid( A.Grid() );
#endif
    const elem::Grid& g = this->Grid();
    this->ResizeTo( A.Height(), A.Width() );
    if( !this->Participating() )
        return *this;

    const Int p = g.Size();
    const Int lcm = g.LCM();
    const Int ownerPath = A.diagPath_;
    const Int ownerPathRank = A.rowAlignment_;

    const Int height = this->Height();
    const Int width = this->Width();
    const Int localWidth = A.LocalWidth();
    const Int maxLocalWidth = MaxLength( width, lcm );
    const Int portionSize = mpi::Pad( height*maxLocalWidth );

    // Since a MD communicator has not been implemented, we will take
    // the suboptimal route of 'rounding up' everyone's contribution over 
    // the VC communicator.
    T* buffer = this->auxMemory_.Require( (p+1)*portionSize );
    T* sendBuf = &buffer[0];
    T* recvBuf = &buffer[portionSize];

    // Pack
    if( A.Participating() )
    {
        const Int ALDim = A.LDim();
        const T* ABuf = A.LockedBuffer();
        PARALLEL_FOR
        for( Int jLoc=0; jLoc<localWidth; ++jLoc )
            MemCopy( &sendBuf[jLoc*height], &ABuf[jLoc*ALDim], height );
    }

    // Communicate
    mpi::AllGather
    ( sendBuf, portionSize,
      recvBuf, portionSize, g.VCComm() );

    // Unpack
    T* thisBuf = this->Buffer();
    const Int thisLDim = this->LDim();
    OUTER_PARALLEL_FOR
    for( Int k=0; k<p; ++k )
    {
        if( g.DiagPath( k ) == ownerPath )
        {
            const T* data = &recvBuf[k*portionSize];
            const Int thisPathRank = g.DiagPathRank( k );
            const Int thisRowShift = Shift_( thisPathRank, ownerPathRank, lcm );
            const Int thisLocalWidth = Length_( width, thisRowShift, lcm );
            INNER_PARALLEL_FOR
            for( Int jLoc=0; jLoc<thisLocalWidth; ++jLoc )
                MemCopy
                ( &thisBuf[(thisRowShift+jLoc*lcm)*thisLDim], 
                  &data[jLoc*height], height );
        }
    }
    this->auxMemory_.Release();
    return *this;
}
コード例 #17
0
ファイル: AllGather.cpp プロジェクト: bluehope/Elemental
void AllGather
( const DistMatrix<T,        U,           V   >& A, 
        DistMatrix<T,Collect<U>(),Collect<V>()>& B ) 
{
    DEBUG_ONLY(CSE cse("copy::AllGather"))
    AssertSameGrids( A, B );

    const Int height = A.Height();
    const Int width = A.Width();
    B.SetGrid( A.Grid() );
    B.Resize( height, width );

    if( A.Participating() )
    {
        const Int colStride = A.ColStride();
        const Int rowStride = A.RowStride();
        const Int distStride = colStride*rowStride;
        const Int maxLocalHeight = MaxLength(height,colStride);
        const Int maxLocalWidth = MaxLength(width,rowStride);
        const Int portionSize = mpi::Pad( maxLocalHeight*maxLocalWidth );
        vector<T> buf( (distStride+1)*portionSize );
        T* sendBuf = &buf[0];
        T* recvBuf = &buf[portionSize];

        // Pack
        util::InterleaveMatrix
        ( A.LocalHeight(), A.LocalWidth(),
          A.LockedBuffer(), 1, A.LDim(),
          sendBuf,          1, A.LocalHeight() );

        // Communicate
        mpi::AllGather
        ( sendBuf, portionSize, recvBuf, portionSize, A.DistComm() );

        // Unpack
        util::StridedUnpack
        ( height, width,
          A.ColAlign(), colStride,
          A.RowAlign(), rowStride,
          recvBuf, portionSize,
          B.Buffer(), B.LDim() );
    }
    if( A.Grid().InGrid() && A.CrossComm() != mpi::COMM_SELF )
    {
        // Pack from the root
        const Int BLocalHeight = B.LocalHeight();
        const Int BLocalWidth = B.LocalWidth();
        vector<T> buf(BLocalHeight*BLocalWidth);
        if( A.CrossRank() == A.Root() )
            util::InterleaveMatrix
            ( BLocalHeight, BLocalWidth,
              B.LockedBuffer(), 1, B.LDim(),
              buf.data(),       1, BLocalHeight ); 

        // Broadcast from the root
        mpi::Broadcast
        ( buf.data(), BLocalHeight*BLocalWidth, A.Root(), A.CrossComm() );

        // Unpack if not the root
        if( A.CrossRank() != A.Root() )
            util::InterleaveMatrix
            ( BLocalHeight, BLocalWidth,
              buf.data(), 1, BLocalHeight,
              B.Buffer(), 1, B.LDim() );
    }
}
コード例 #18
0
ファイル: ColAllToAllDemote.cpp プロジェクト: sg0/Elemental
void ColAllToAllDemote
( const DistMatrix<T,Partial<U>(),PartialUnionRow<U,V>()>& A,
        DistMatrix<T,        U,                     V   >& B )
{
    DEBUG_ONLY(CallStackEntry cse("copy::ColAllToAllDemote"))
    AssertSameGrids( A, B );

    const Int height = A.Height();
    const Int width = A.Width();
    B.AlignColsAndResize( A.ColAlign(), height, width, false, false );
    if( !B.Participating() )
        return;

    const Int colAlign = B.ColAlign();
    const Int rowAlignA = A.RowAlign();

    const Int colStride = B.ColStride();
    const Int colStridePart = B.PartialColStride();
    const Int colStrideUnion = B.PartialUnionColStride();
    const Int colRankPart = B.PartialColRank();
    const Int colDiff = (colAlign%colStridePart) - A.ColAlign();

    const Int colShiftA = A.ColShift();

    const Int localHeightB = B.LocalHeight();
    const Int localWidthA = A.LocalWidth();
    const Int maxLocalHeight = MaxLength(height,colStride);
    const Int maxLocalWidth = MaxLength(width,colStrideUnion);
    const Int portionSize = mpi::Pad( maxLocalHeight*maxLocalWidth );

    std::vector<T> buffer( 2*colStrideUnion*portionSize );
    T* firstBuf  = &buffer[0];
    T* secondBuf = &buffer[colStrideUnion*portionSize];

    if( colDiff == 0 )
    {
        // Pack            
        util::PartialColStridedPack
        ( height, localWidthA,
          colAlign, colStride, 
          colStrideUnion, colStridePart, colRankPart,
          colShiftA,
          A.LockedBuffer(), A.LDim(),
          firstBuf,         portionSize );

        // Simultaneously Scatter in columns and Gather in rows
        mpi::AllToAll
        ( firstBuf,  portionSize,
          secondBuf, portionSize, B.PartialUnionColComm() );

        // Unpack
        util::RowStridedUnpack
        ( localHeightB, width,
          rowAlignA, colStrideUnion,
          secondBuf, portionSize,
          B.Buffer(), B.LDim() );
    }
    else
    {
#ifdef EL_UNALIGNED_WARNINGS
        if( B.Grid().Rank() == 0 )
            std::cerr << "Unaligned ColAllToAllDemote" << std::endl;
#endif
        const Int sendColRankPart = Mod( colRankPart+colDiff, colStridePart );
        const Int recvColRankPart = Mod( colRankPart-colDiff, colStridePart );

        // Pack
        util::PartialColStridedPack
        ( height, localWidthA,
          colAlign, colStride, 
          colStrideUnion, colStridePart, sendColRankPart,
          colShiftA,
          A.LockedBuffer(), A.LDim(),
          secondBuf,        portionSize );

        // Simultaneously Scatter in columns and Gather in rows
        mpi::AllToAll
        ( secondBuf, portionSize,
          firstBuf,  portionSize, B.PartialUnionColComm() );

        // Realign the result
        mpi::SendRecv
        ( firstBuf,  colStrideUnion*portionSize, sendColRankPart,
          secondBuf, colStrideUnion*portionSize, recvColRankPart,
          B.PartialColComm() );

        // Unpack
        util::RowStridedUnpack
        ( localHeightB, width,
          rowAlignA, colStrideUnion,
          secondBuf, portionSize,
          B.Buffer(), B.LDim() );
    }
}
コード例 #19
0
ファイル: TransposeDist.hpp プロジェクト: AmiArnab/Elemental
void TransposeDist( const DistMatrix<T,U,V>& A, DistMatrix<T,V,U>& B ) 
{
    DEBUG_ONLY(CSE cse("copy::TransposeDist"))
    AssertSameGrids( A, B );

    const Grid& g = B.Grid();
    B.Resize( A.Height(), A.Width() );
    if( !B.Participating() )
        return;

    const Int colStrideA = A.ColStride();
    const Int rowStrideA = A.RowStride();
    const Int distSize = A.DistSize();

    if( A.DistSize() == 1 && B.DistSize() == 1 ) 
    {
        Copy( A.LockedMatrix(), B.Matrix() );
    }
    else if( A.Width() == 1 )
    {
        const Int height = A.Height();
        const Int maxLocalHeight = MaxLength(height,distSize);
        const Int portionSize = mpi::Pad( maxLocalHeight );

        const Int colDiff = Shift(A.DistRank(),A.ColAlign(),distSize) - 
                            Shift(B.DistRank(),B.ColAlign(),distSize);
        const Int sendRankB = Mod( B.DistRank()+colDiff, distSize );
        const Int recvRankA = Mod( A.DistRank()-colDiff, distSize );
        const Int recvRankB = 
            (recvRankA/colStrideA)+rowStrideA*(recvRankA%colStrideA);

        vector<T> buffer;
        FastResize( buffer, (colStrideA+rowStrideA)*portionSize );
        T* sendBuf = &buffer[0];
        T* recvBuf = &buffer[colStrideA*portionSize];

        if( A.RowRank() == A.RowAlign() )
        {
            // Pack
            // TODO: Use kernel from copy::util
            const Int AColShift = A.ColShift();
            const T* ABuf = A.LockedBuffer();
            EL_PARALLEL_FOR
            for( Int k=0; k<rowStrideA; ++k )
            {
                T* data = &recvBuf[k*portionSize];

                const Int shift = 
                  Shift_(A.ColRank()+colStrideA*k,A.ColAlign(),distSize);
                const Int offset = (shift-AColShift) / colStrideA;
                const Int thisLocalHeight = Length_(height,shift,distSize);

                for( Int iLoc=0; iLoc<thisLocalHeight; ++iLoc )
                    data[iLoc] = ABuf[offset+iLoc*rowStrideA];
            }
        }

        // (e.g., A[VC,STAR] <- A[MC,MR])
        mpi::Scatter
        ( recvBuf, portionSize,
          sendBuf, portionSize, A.RowAlign(), A.RowComm() );

        // (e.g., A[VR,STAR] <- A[VC,STAR])
        mpi::SendRecv
        ( sendBuf, portionSize, sendRankB,
          recvBuf, portionSize, recvRankB, B.DistComm() );

        // (e.g., A[MR,MC] <- A[VR,STAR])
        mpi::Gather
        ( recvBuf, portionSize,
          sendBuf, portionSize, B.RowAlign(), B.RowComm() );

        if( B.RowRank() == B.RowAlign() )
        {
            // Unpack
            // TODO: Use kernel from copy::util
            T* bufB = B.Buffer();
            EL_PARALLEL_FOR
            for( Int k=0; k<colStrideA; ++k )
            {
                const T* data = &sendBuf[k*portionSize];

                const Int shift = 
                  Shift_(B.ColRank()+rowStrideA*k,B.ColAlign(),distSize);
                const Int offset = (shift-B.ColShift()) / rowStrideA;
                const Int thisLocalHeight = Length_(height,shift,distSize);

                for( Int iLoc=0; iLoc<thisLocalHeight; ++iLoc )
                    bufB[offset+iLoc*colStrideA] = data[iLoc];
            }
        }
    }
コード例 #20
0
ファイル: lbann_layer.cpp プロジェクト: linan7788626/lbann
void Write_MPI(const DistMatrix<DataType> &M, std::string basename = "DistMatrix", FileFormat format = BINARY, std::string title = "")
{
    // TODO: error out if format != BINARY

    // TODO: use TypeMap<>() and templating to figure this out
    MPI_Datatype type = DataTypeMPI;

    // define our file name
    string filename = basename + "." + FileExtension(BINARY);
    const char* path = filename.c_str();

    // get MPI communicator
    MPI_Comm comm = M.Grid().Comm().comm;

    // get our rank
    int rank = M.Grid().Rank();

    // first, delete the existing file
    if (rank == 0) {
        /*
        int unlink_rc = unlink(path);
        if (unlink_rc != 0) {
            fprintf(stderr, "Error deleting file `%s'\n", path);
            fflush(stderr);
        }
        */
        MPI_File_delete(path, MPI_INFO_NULL);
    }

    // get global width and height of matrix
    Int global_width  = M.Width();
    Int global_height = M.Height();

    // define datatypes to describe local buffer and view into file
    MPI_Datatype mattype, viewtype;
    create_types(M, &mattype, &viewtype);

    // define hints for creating the file (e.g., number of stripes on Lustre)
    MPI_Info info;
    MPI_Info_create(&info);
    MPI_Info_set(info, "striping_factor", "10");
    //MPI_Info_set(info, "striping_factor", "80");

    // open the file
    MPI_File fh;
    MPI_Status status;
    char datarep[] = "native";
    int amode = MPI_MODE_WRONLY | MPI_MODE_CREATE;
    MPI_File_open(comm, path, amode, info, &fh);

    // done with the info object
    MPI_Info_free(&info);

    // truncate file to 0 bytes
//    MPI_File_set_size(fh, 0);

    // set our view to write header (height and width as unsigned 32-bit ints)
    MPI_Offset disp = 0;
    MPI_File_set_view(fh, disp, MPI_UINT32_T, MPI_UINT32_T, datarep, MPI_INFO_NULL);
    if (rank == 0) {
        uint32_t dimensions[2];
        dimensions[0] = global_height;
        dimensions[1] = global_width;
        MPI_File_write_at(fh, 0, dimensions, 2, MPI_UINT32_T, &status);
    }
    disp += 2 * sizeof(uint32_t);

    // set view to write data
    MPI_File_set_view(fh, disp, type, viewtype, datarep, MPI_INFO_NULL);

    // write our portion of the matrix, since we set our view using create_darray,
    // all procs write at offset 0, the file view will take care of interleaving appropriately
    const char* buf = (const char*) M.LockedBuffer();
    MPI_File_write_at_all(fh, 0, buf, 1, mattype, &status);

    // close file
    MPI_File_close(&fh);

    // free our datatypes
    MPI_Type_free(&mattype);
    MPI_Type_free(&viewtype);

    return;
}
コード例 #21
0
ファイル: Scatter.hpp プロジェクト: YingzhouLi/Elemental
void Scatter
( const DistMatrix<T,CIRC,CIRC>& A,
        ElementalMatrix<T>& B )
{
    DEBUG_CSE
    AssertSameGrids( A, B );

    const Int m = A.Height();
    const Int n = A.Width();
    const Int colStride = B.ColStride();
    const Int rowStride = B.RowStride();
    B.Resize( m, n );
    if( B.CrossSize() != 1 || B.RedundantSize() != 1 )
    {
        // TODO:
        // Broadcast over the redundant communicator and use mpi::Translate
        // rank to determine whether a process is the root of the broadcast.
        GeneralPurpose( A, B ); 
        return;
    }

    const Int pkgSize = mpi::Pad(MaxLength(m,colStride)*MaxLength(n,rowStride));
    const Int recvSize = pkgSize;
    const Int sendSize = B.DistSize()*pkgSize;

    // Translate the root of A into the DistComm of B (if possible)
    const Int root = A.Root();
    const Int target = mpi::Translate( A.CrossComm(), root, B.DistComm() ); 
    if( target == mpi::UNDEFINED )
        return;

    if( B.DistSize() == 1 )
    {
        Copy( A.LockedMatrix(), B.Matrix() );
        return;
    }

    vector<T> buffer;
    T* recvBuf=0; // some compilers (falsely) warn otherwise
    if( A.CrossRank() == root )
    {
        FastResize( buffer, sendSize+recvSize );
        T* sendBuf = &buffer[0];
        recvBuf    = &buffer[sendSize];

        // Pack the send buffer
        copy::util::StridedPack
        ( m, n,
          B.ColAlign(), colStride,
          B.RowAlign(), rowStride,
          A.LockedBuffer(), A.LDim(),
          sendBuf,          pkgSize );

        // Scatter from the root
        mpi::Scatter
        ( sendBuf, pkgSize, recvBuf, pkgSize, target, B.DistComm() );
    }
    else
    {
        FastResize( buffer, recvSize );
        recvBuf = &buffer[0];

        // Perform the receiving portion of the scatter from the non-root
        mpi::Scatter
        ( static_cast<T*>(0), pkgSize,
          recvBuf,            pkgSize, target, B.DistComm() );
    }

    // Unpack
    copy::util::InterleaveMatrix
    ( B.LocalHeight(), B.LocalWidth(),
      recvBuf,    1, B.LocalHeight(),
      B.Buffer(), 1, B.LDim() );
}