void Scatter
( T alpha,
const ElementalMatrix<T>& A,
ElementalMatrix<T>& B )
{
DEBUG_ONLY(CSE cse("axpy_contract::Scatter"))
AssertSameGrids( A, B );
if( A.Height() != B.Height() || A.Width() != B.Width() )
LogicError("Sizes of A and B must match");
if( !B.Participating() )
return;
const Int colStride = B.ColStride();
const Int rowStride = B.RowStride();
const Int colAlign = B.ColAlign();
const Int rowAlign = B.RowAlign();
const Int height = B.Height();
const Int width = B.Width();
const Int localHeight = B.LocalHeight();
const Int localWidth = B.LocalWidth();
const Int maxLocalHeight = MaxLength(height,colStride);
const Int maxLocalWidth = MaxLength(width,rowStride);
const Int recvSize = mpi::Pad( maxLocalHeight*maxLocalWidth );
const Int sendSize = colStride*rowStride*recvSize;
//vector<T> buffer( sendSize );
vector<T> buffer;
buffer.reserve( sendSize );
// Pack
copy::util::StridedPack
( height, width,
colAlign, colStride,
rowAlign, rowStride,
A.LockedBuffer(), A.LDim(),
buffer.data(), recvSize );
// Communicate
mpi::ReduceScatter( buffer.data(), recvSize, B.DistComm() );
// Unpack our received data
axpy::util::InterleaveMatrixUpdate
( alpha, localHeight, localWidth,
buffer.data(), 1, localHeight,
B.Buffer(), 1, B.LDim() );
}
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() );
}