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Grid/Grid_mpi_cshift.h
Peter Boyle 98f14f1030 Fixing the Checkerboarding cshift. 
Implemented "fake" communications in preparation for the leap to MPI.
2015-03-29 20:35:37 +01:00

385 lines
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#ifndef _GRID_MPI_CSHIFT_H_
#define _GRID_MPI_CSHIFT_H_
//////////////////////////////////////////////
// Q. Split this into seperate sub functions?
//////////////////////////////////////////////
// CshiftCB_comms_splice
// CshiftCB_comms
// CshiftCB_local
// CshiftCB_local_permute
// Cshift_comms_splice
// Cshift_comms
// Cshift_local
// Cshift_local_permute
// Broadly I remain annoyed that the iteration is so painful
// for red black data layout, when simple block strided descriptors suffice for non-cb.
//
// The other option is to do it table driven, or perhaps store the CB of each site in a table.
//
// Must not lose sight that goal is to be able to construct really efficient
// gather to a point stencil code. CSHIFT is not the best way, so probably need
// additional stencil support.
//
// Could still do a templated syntax tree and make CSHIFT return lattice vector.
//
// Stencil based code could pre-exchange haloes and use a table lookup for neighbours
//
// Lattice <foo> could also allocate haloes which get used for stencil code.
//
// Grid could create a neighbour index table for a given stencil.
// Could also implement CovariantCshift.
//////////////////////////////////////////////////////
//Non checkerboarded support functions
//////////////////////////////////////////////////////
friend void Gather_plane (Lattice<vobj> &rhs,std::vector<vobj> &buffer, int dimension,int plane)
{
const int Nsimd = vector_type::Nsimd();
int rd = rhs._grid->_rdimensions[dimension];
int so = plane*rhs._grid->_ostride[dimension]; // base offset for start of plane
int o = 0; // relative offset to base within plane
#pragma omp parallel for collapse(2)
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
int so = sx*rhs._grid->_ostride[dimension];
int permute_slice=0;
int wrap = sshift/rd;
int num = sshift%rd;
if ( x< rd-num ) permute_slice=wrap;
else permute_slice = 1-wrap;
if ( permute_slice ) {
permute(ret._odata[ro+o+b],rhs._odata[so+o+b],permute_type);
} else {
ret._odata[ro+o+b]=rhs._odata[so+o+b];
}
}
o +=rhs._grid->_slice_stride[dimension];
}
}
}
//friend void Gather_plane_extract(Lattice<vobj> &rhs,std::vector<scalar_type *> pointers,int dimension,int plane);
//
//friend void Scatter_plane (Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
//friend void Scatter_plane_merge (Lattice<vobj> &rhs,std::vector<scalar_type *> pointers,int dimension,int plane);
//
//template<int permute_type> friend void Copy_plane_permute(Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
// friend void Copy_plane(Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
//
//////////////////////////////////////////////////////
//Checkerboarded support functions
//////////////////////////////////////////////////////
//friend void GatherCB_plane (Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
//friend void GatherCB_plane_extract(Lattice<vobj> &rhs,std::vector<scalar_type *> pointers,int dimension,int plane);
//
//friend void ScatterCB_plane (Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
//friend void ScatterCB_plane_merge (Lattice<vobj> &rhs,std::vector<scalar_type *> pointers,int dimension,int plane);
//
//template<int permute_type> friend void CopyCB_plane_permute(Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
// friend void Copy_plane(Lattice<vobj> &rhs,std::vector<vobj> face, int dimension,int plane);
friend Lattice<vobj> Cshift(Lattice<vobj> &rhs,int dimension,int shift)
{
typedef typename vobj::vector_type vector_type;
typedef typename vobj::scalar_type scalar_type;
const int Nsimd = vector_type::Nsimd();
Lattice<vobj> ret(rhs._grid);
int fd = rhs._grid->_fdimensions[dimension];
int rd = rhs._grid->_rdimensions[dimension];
//int ld = rhs._grid->_ldimensions[dimension];
//int gd = rhs._grid->_gdimensions[dimension];
// Map to always positive shift modulo global full dimension.
shift = (shift+fd)%fd;
ret.checkerboard = rhs._grid->CheckerBoardDestination(rhs.checkerboard,shift);
// the permute type
int simd_layout = rhs._grid->_simd_layout[dimension];
int comm_dim = rhs._grid->_processors[dimension] >1 ;
int permute_dim = rhs._grid->_simd_layout[dimension]>1 && (!comm_dim);
int splice_dim = rhs._grid->_simd_layout[dimension]>1 && (comm_dim);
int permute_type=0;
for(int d=0;d<dimension;d++){
if (rhs._grid->_simd_layout[d]>1 ) permute_type++;
}
// Logic for non-distributed dimension
std::vector<int> comm_offnode(simd_layout);
std::vector<int> comm_to (simd_layout);
std::vector<int> comm_from (simd_layout);
std::vector<int> comm_rx (simd_layout); // reduced coordinate of neighbour plane
std::vector<int> comm_simd_lane(simd_layout);// simd lane of neigbour plane
///////////////////////////////////////////////
// Move via a fake comms buffer
// Simd direction uses an extract/merge pair
///////////////////////////////////////////////
int buffer_size = rhs._grid->_slice_nblock[dimension]*rhs._grid->_slice_block[dimension];
int words = sizeof(vobj)/sizeof(vector_type);
std::vector<vobj,alignedAllocator<vobj> > comm_buf(buffer_size);
std::vector<std::vector<scalar_type> > comm_buf_extract(Nsimd,std::vector<scalar_type>(buffer_size*words) );
std::vector<scalar_type *> pointers(Nsimd);
if ( permute_dim ) {
for(int x=0;x<rd;x++){
int ro = x*rhs._grid->_ostride[dimension]; // base offset for result
int o = 0; // relative offset to base
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
int so = sx*rhs._grid->_ostride[dimension];
int permute_slice=0;
int wrap = sshift/rd;
int num = sshift%rd;
if ( x< rd-num ) permute_slice=wrap;
else permute_slice = 1-wrap;
if ( permute_slice ) {
permute(ret._odata[ro+o+b],rhs._odata[so+o+b],permute_type);
} else {
ret._odata[ro+o+b]=rhs._odata[so+o+b];
}
}
o +=rhs._grid->_slice_stride[dimension];
}
}
} else if ( splice_dim ) {
if ( rhs._grid->_simd_layout[dimension] > 2 ) exit(-1); // use Cassert. Audit code for exit and replace
if ( rhs._grid->_simd_layout[dimension] < 1 ) exit(-1);
for(int i=0;i<vobj::vector_type::Nsimd();i++){
pointers[i] = (scalar_type *)&comm_buf_extract[i][0];
}
for(int x=0;x<rd;x++){
///////////////////////////////////////////
// Extract one orthogonal slice at a time
///////////////////////////////////////////
int ro = x*rhs._grid->_ostride[dimension]; // base offset for result
o = 0; // relative offset to base
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
// base offset for source
int so = sx*rhs._grid->_ostride[dimension];
int permute_slice=0;
int wrap = sshift/rd;
int num = sshift%rd;
if ( x< rd-num ) permute_slice=wrap;
else permute_slice = 1-wrap;
if ( permute_slice ) {
extract(rhs._odata[so+o+b],pointers);
}
}
o +=rhs._grid->_slice_stride[dimension];
}
///////////////////////////////////////////
// Work out what to send where
///////////////////////////////////////////
for(int s=0;s<simd_layout;s++) {
// shift to "neighbour" takes us off node
// coordinates (rx, simd_lane) of neighbour
// how many nodes away is this shift
// where we should send to
// where we should receive from
int shifted_x = x+s*rd+shift;
comm_offnode[s] = shifted_x > ld;
comm_send_rx[s] = shifted_x%rd; // which slice geton the other node
comm_send_simd_lane [s] = shifted_x/rd; // which slice on the other node
comm_from[s] = shifted_x/ld;
comm_to [s] = (2*_processors[dimension]-comm_from[s]) % _processors[dimension];
comm_from[s] = (comm_from[s]+_processors[dimension]) % _processors[dimension];
}
////////////////////////////////////////////////
// Insert communication phase
////////////////////////////////////////////////
#if 0
} else if (comm_dim ) {
// Packed gather sequence is clean
int buffer_size = rhs._grid->_slice_nblock[dimension]*rhs._grid->_slice_nblock[dimension];
std::vector<vobj,alignedAllocator<vobj> > send_buf(buffer_size);
std::vector<vobj,alignedAllocator<vobj> > recv_buf(buffer_size);
// off node; communcate slice (ld==rd)
if ( x+shift > rd ) {
int sb=0;
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int i=0;i<rhs._grid->_slice_block[dimension];i++){
send_buf[sb++]=rhs._odata[so+i];
}
so+=rhs._grid->_slice_stride[dimension];
}
// Make a comm_fake them mimics comms in periodic case.
// scatter face
int rb=0;
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int i=0;i<rhs._grid->_slice_block[dimension];i++){
ret._odata[so+i]=recv_buf[rb++];
}
so+=rhs._grid->_slice_stride[dimension];
}
} else {
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int i=0;i<rhs._grid->_slice_block[dimension];i++){
ret._odata[o+i]=rhs._odata[so+i];
}
o+=rhs._grid->_slice_stride[dimension];
so+=rhs._grid->_slice_stride[dimension];
}
}
#endif
////////////////////////////////////////////////
// Pull receive buffers and permuted buffers in
////////////////////////////////////////////////
for(int i=0;i<vobj::vector_type::Nsimd();i++){
pointers[i] = (scalar_type *)&comm_buf_extract[permute_map[permute_type][i]][0];
}
o = 0; // relative offset to base
int ro = x*rhs._grid->_ostride[dimension]; // base offset for result
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
// base offset for source
int so = sx*rhs._grid->_ostride[dimension];
int permute_slice=0;
int wrap = sshift/rd;
int num = sshift%rd;
if ( x< rd-num ) permute_slice=wrap;
else permute_slice = 1-wrap;
if ( permute_slice ) {
merge(ret._odata[ro+o+b],pointers);
}
}
o +=rhs._grid->_slice_stride[dimension];
}
}
} else if ( comm_dim ) {
int co; // comm offset
int o;
co=0;
for(int x=0;x<rd;x++){
o=0;
int ro = x*rhs._grid->_ostride[dimension]; // base offset for result
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
// This call in inner loop is annoying but necessary for dimension=0
// in the case of RedBlack grids. Could optimise away with
// alternate code paths for all other cases.
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
int so = sx*rhs._grid->_ostride[dimension];
comm_buf[co++]=rhs._odata[so+o+b];
}
o +=rhs._grid->_slice_stride[dimension];
}
// Step through a copy into a comms buffer and pull back in.
// Genuine fake implementation could calculate if loops back
co=0; o=0;
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
ret._odata[ro+o+b]=comm_buf[co++];
}
o +=rhs._grid->_slice_stride[dimension];
}
}
} else { // Local dimension, no permute required
for(int x=0;x<rd;x++){
int o=0;
int ro = x*rhs._grid->_ostride[dimension]; // base offset for result
for(int n=0;n<rhs._grid->_slice_nblock[dimension];n++){
for(int b=0;b<rhs._grid->_slice_block[dimension];b++){
// This call in inner loop is annoying but necessary for dimension=0
// in the case of RedBlack grids. Could optimise away with
// alternate code paths for all other cases.
int sshift = rhs._grid->CheckerBoardShift(rhs.checkerboard,dimension,shift,o+b);
int sx = (x+sshift)%rd;
int so = sx*rhs._grid->_ostride[dimension];
ret._odata[bo+o+b]=rhs._odata[so+o+b];
}
o +=rhs._grid->_slice_stride[dimension];
}
}
}
return ret;
}
#endif
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