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https://github.com/paboyle/Grid.git
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364 lines
10 KiB
C++
364 lines
10 KiB
C++
#ifndef GRID_STENCIL_H
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#define GRID_STENCIL_H
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//////////////////////////////////////////////////////////////////////////////////////////
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// Must not lose sight that goal is to be able to construct really efficient
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// gather to a point stencil code. CSHIFT is not the best way, so probably need
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// additional stencil support.
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//
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// Stencil based code could pre-exchange haloes and use a table lookup for neighbours
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//
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// Lattice <foo> could also allocate haloes which get used for stencil code.
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//
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// Grid could create a neighbour index table for a given stencil.
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//
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// Could also implement CovariantCshift, to fuse the loops and enhance performance.
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//
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//
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// General stencil computation:
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//
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// Generic services
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// 0) Prebuild neighbour tables
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// 1) Compute sizes of all haloes/comms buffers; allocate them.
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//
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// 2) Gather all faces, and communicate.
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// 3) Loop over result sites, giving nbr index/offnode info for each
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//
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// Could take a
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// SpinProjectFaces
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// start comms
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// complete comms
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// Reconstruct Umu
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//
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// Approach.
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//
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//////////////////////////////////////////////////////////////////////////////////////////
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namespace Grid {
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class Stencil {
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public:
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Stencil(GridBase *grid,
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int npoints,
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int checkerboard,
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std::vector<int> directions,
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std::vector<int> distances);
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void Stencil_local (int dimension,int shift,int cbmask);
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void Stencil_comms (int dimension,int shift,int cbmask);
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void Stencil_comms_simd(int dimension,int shift,int cbmask);
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// Will need to implement actions for
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Copy_plane;
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Copy_plane_permute;
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Gather_plane;
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// The offsets to all neibours in stencil in each direction
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int _checkerboard;
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int _npoints; // Move to template param?
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GridBase * _grid;
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// Store these as SIMD Integer needed
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//
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// std::vector< iVector<Integer, Npoint> > _offsets;
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// std::vector< iVector<Integer, Npoint> > _local;
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// std::vector< iVector<Integer, Npoint> > _comm_buf_size;
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// std::vector< iVector<Integer, Npoint> > _permute;
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std::vector<std::vector<int> > _offsets;
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std::vector<std::vector<int> > _local;
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std::vector<int> _comm_buf_size;
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std::vector<int> _permute;
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};
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Stencil::Stencil(GridBase *grid,
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int npoints,
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int checkerboard,
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std::vector<int> directions,
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std::vector<int> distances){
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_npoints = npoints;
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_grid = grid;
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for(int i=0;i<npoints;i++){
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int dimension = directions[i];
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int displacement = distances[i];
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int fd = _grid->_fdimensions[dimension];
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int rd = _grid->_rdimensions[dimension];
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_checkerboard = checkerboard;
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// the permute type
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int simd_layout = _grid->_simd_layout[dimension];
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int comm_dim = _grid->_processors[dimension] >1 ;
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int splice_dim = _grid->_simd_layout[dimension]>1 && (comm_dim);
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int sshift[2];
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if ( !comm_dim ) {
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sshift[0] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,0);
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sshift[1] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,1);
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if ( sshift[0] == sshift[1] ) {
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Stencil_local(dimension,shift,0x3);
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} else {
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Stencil_local(dimension,shift,0x1);// if checkerboard is unfavourable take two passes
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Stencil_local(dimension,shift,0x2);// both with block stride loop iteration
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}
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} else if ( splice_dim ) {
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sshift[0] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,0);
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sshift[1] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,1);
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if ( sshift[0] == sshift[1] ) {
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Stencil_comms_simd(dimension,shift,0x3);
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} else {
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Stencil_comms_simd(dimension,shift,0x1);// if checkerboard is unfavourable take two passes
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Stencil_comms_simd(dimension,shift,0x2);// both with block stride loop iteration
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}
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} else {
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// Cshift_comms(ret,rhs,dimension,shift);
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sshift[0] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,0);
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sshift[1] = _grid->CheckerBoardShift(_checkerboard,dimension,shift,1);
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if ( sshift[0] == sshift[1] ) {
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Stencil_comms(dimension,shift,0x3);
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} else {
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Stencil_comms(dimension,shift,0x1);// if checkerboard is unfavourable take two passes
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Stencil_comms(dimension,shift,0x2);// both with block stride loop iteration
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}
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}
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}
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}
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void Stencil::Stencil_local (int dimension,int shift,int cbmask)
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{
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int fd = _grid->_fdimensions[dimension];
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int rd = _grid->_rdimensions[dimension];
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int ld = _grid->_ldimensions[dimension];
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int gd = _grid->_gdimensions[dimension];
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// Map to always positive shift modulo global full dimension.
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shift = (shift+fd)%fd;
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// the permute type
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int permute_dim =_grid->PermuteDim(dimension);
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int permute_type=_grid->PermuteType(dimension);
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for(int x=0;x<rd;x++){
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int o = 0;
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int bo = x * _grid->_ostride[dimension];
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int cb= (cbmask==0x2)? 1 : 0;
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int sshift = _grid->CheckerBoardShift(_checkerboard,dimension,shift,cb);
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int sx = (x+sshift)%rd;
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int permute_slice=0;
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if(permute_dim){
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int wrap = sshift/rd;
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int num = sshift%rd;
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if ( x< rd-num ) permute_slice=wrap;
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else permute_slice = 1-wrap;
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}
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if ( permute_slice ) Copy_plane_permute(dimension,x,sx,cbmask,permute_type);
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else Copy_plane (dimension,x,sx,cbmask);
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}
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}
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void Stencil::Stencil_comms (int dimension,int shift,int cbmask)
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{
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typedef typename vobj::vector_type vector_type;
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typedef typename vobj::scalar_type scalar_type;
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GridBase *grid=_grid;
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int fd = _grid->_fdimensions[dimension];
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int rd = _grid->_rdimensions[dimension];
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int simd_layout = _grid->_simd_layout[dimension];
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int comm_dim = _grid->_processors[dimension] >1 ;
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assert(simd_layout==1);
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assert(comm_dim==1);
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assert(shift>=0);
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assert(shift<fd);
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int buffer_size = _grid->_slice_nblock[dimension]*rhs._grid->_slice_block[dimension];
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// FIXME: Do something with buffer_size??
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int cb= (cbmask==0x2)? 1 : 0;
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int sshift= _grid->CheckerBoardShift(_checkerboard,dimension,shift,cb);
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for(int x=0;x<rd;x++){
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int offnode = ( x+sshift >= rd );
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int sx = (x+sshift)%rd;
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int comm_proc = (x+sshift)/rd;
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if (!offnode) {
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Copy_plane(dimension,x,sx,cbmask);
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} else {
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int words = send_buf.size();
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if (cbmask != 0x3) words=words>>1;
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int bytes = words * sizeof(vobj);
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Gather_plane_simple (dimension,sx,cbmask);
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int rank = grid->_processor;
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int recv_from_rank;
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int xmit_to_rank;
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grid->ShiftedRanks(dimension,comm_proc,xmit_to_rank,recv_from_rank);
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/*
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grid->SendToRecvFrom((void *)&send_buf[0],
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xmit_to_rank,
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(void *)&recv_buf[0],
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recv_from_rank,
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bytes);
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*/
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Scatter_plane_simple (dimension,x,cbmask);
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}
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}
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}
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void Stencil::Stencil_comms_simd(int dimension,int shift,int cbmask)
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{
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GridBase *grid=_grid;
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const int Nsimd = _grid->Nsimd();
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typedef typename vobj::vector_type vector_type;
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typedef typename vobj::scalar_type scalar_type;
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int fd = _grid->_fdimensions[dimension];
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int rd = _grid->_rdimensions[dimension];
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int ld = _grid->_ldimensions[dimension];
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int simd_layout = _grid->_simd_layout[dimension];
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int comm_dim = _grid->_processors[dimension] >1 ;
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assert(comm_dim==1);
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assert(simd_layout==2);
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assert(shift>=0);
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assert(shift<fd);
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int permute_type=_grid->PermuteType(dimension);
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///////////////////////////////////////////////
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// Simd direction uses an extract/merge pair
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///////////////////////////////////////////////
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int buffer_size = _grid->_slice_nblock[dimension]*grid->_slice_block[dimension];
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// FIXME do something with buffer size
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std::vector<scalar_type *> pointers(Nsimd); //
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std::vector<scalar_type *> rpointers(Nsimd); // received pointers
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///////////////////////////////////////////
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// Work out what to send where
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///////////////////////////////////////////
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int cb = (cbmask==0x2)? 1 : 0;
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int sshift= _grid->CheckerBoardShift(_checkerboard,dimension,shift,cb);
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std::vector<int> comm_offnode(simd_layout);
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std::vector<int> comm_proc (simd_layout); //relative processor coord in dim=dimension
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std::vector<int> icoor(grid->Nd());
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for(int x=0;x<rd;x++){
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int comm_any = 0;
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for(int s=0;s<simd_layout;s++) {
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int shifted_x = x+s*rd+sshift;
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comm_offnode[s] = shifted_x >= ld;
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comm_any = comm_any | comm_offnode[s];
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comm_proc[s] = shifted_x/ld;
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}
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int o = 0;
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int bo = x*grid->_ostride[dimension];
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int sx = (x+sshift)%rd;
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if ( comm_any ) {
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for(int i=0;i<Nsimd;i++){
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pointers[i] = (scalar_type *)&send_buf_extract[i][0];
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}
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Gather_plane_extract(rhs,pointers,dimension,sx,cbmask);
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for(int i=0;i<Nsimd;i++){
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int s;
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grid->iCoorFromIindex(icoor,i);
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s = icoor[dimension];
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if(comm_offnode[s]){
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int rank = grid->_processor;
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int recv_from_rank;
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int xmit_to_rank;
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grid->ShiftedRanks(dimension,comm_proc[s],xmit_to_rank,recv_from_rank);
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/*
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grid->SendToRecvFrom((void *)&send_buf_extract[i][0],
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xmit_to_rank,
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(void *)&recv_buf_extract[i][0],
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recv_from_rank,
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bytes);
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*/
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rpointers[i] = (scalar_type *)&recv_buf_extract[i][0];
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} else {
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rpointers[i] = (scalar_type *)&send_buf_extract[i][0];
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}
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}
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// Permute by swizzling pointers in merge
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int permute_slice=0;
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int lshift=sshift%ld;
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int wrap =lshift/rd;
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int num =lshift%rd;
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if ( x< rd-num ) permute_slice=wrap;
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else permute_slice = 1-wrap;
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int toggle_bit = (Nsimd>>(permute_type+1));
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int PermuteMap;
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for(int i=0;i<Nsimd;i++){
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if ( permute_slice ) {
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PermuteMap=i^toggle_bit;
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pointers[i] = rpointers[PermuteMap];
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} else {
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pointers[i] = rpointers[i];
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}
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}
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Scatter_plane_merge(pointers,dimension,x,cbmask);
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} else {
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int permute_slice=0;
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int wrap = sshift/rd;
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int num = sshift%rd;
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if ( x< rd-num ) permute_slice=wrap;
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else permute_slice = 1-wrap;
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if ( permute_slice ) Copy_plane_permute(ret,rhs,dimension,x,sx,cbmask,permute_type);
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else Copy_plane(ret,rhs,dimension,x,sx,cbmask);
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}
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}
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}
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};
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#endif
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