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Grid/lib/Stencil.h
Peter Boyle c9fadf97a5 Simplify the compressor interface again.
2016-02-17 18:16:45 -06:00

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/*************************************************************************************
Grid physics library, www.github.com/paboyle/Grid
Source file: ./lib/Stencil.h
Copyright (C) 2015
Author: Peter Boyle <paboyle@ph.ed.ac.uk>
This program 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 2 of the License, or
(at your option) any later version.
This program 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 this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
See the full license in the file "LICENSE" in the top level distribution directory
*************************************************************************************/
/* END LEGAL */
#ifndef GRID_STENCIL_H
#define GRID_STENCIL_H
#include <thread>
#include <stencil/Lebesgue.h> // subdir aggregate
//////////////////////////////////////////////////////////////////////////////////////////
// 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 need
// additional stencil support.
//
// Stencil based code will pre-exchange haloes and use a table lookup for neighbours.
// This will be done with generality to allow easier efficient implementations.
// Overlap of comms and compute could be semi-automated by tabulating off-node connected,
// and
//
// 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, to fuse the loops and enhance performance.
//
//
// General stencil computation:
//
// Generic services
// 0) Prebuild neighbour tables
// 1) Compute sizes of all haloes/comms buffers; allocate them.
//
// 2) Gather all faces, and communicate.
// 3) Loop over result sites, giving nbr index/offnode info for each
//
// Could take a
// SpinProjectFaces
// start comms
// complete comms
// Reconstruct Umu
//
// Approach.
//
//////////////////////////////////////////////////////////////////////////////////////////
namespace Grid {
struct StencilEntry {
int _offset;
int _is_local;
int _permute;
int _around_the_world;
};
template<class vobj,class cobj>
class CartesianStencil { // Stencil runs along coordinate axes only; NO diagonal fill in.
public:
typedef uint32_t StencilInteger;
typedef typename cobj::vector_type vector_type;
typedef typename cobj::scalar_type scalar_type;
typedef typename cobj::scalar_object scalar_object;
//////////////////////////////////////////
// Comms packet queue for asynch thread
//////////////////////////////////////////
struct Packet {
void * send_buf;
void * recv_buf;
Integer to_rank;
Integer from_rank;
Integer bytes;
volatile Integer done;
};
std::vector<Packet> Packets;
#define SEND_IMMEDIATE
#define SERIAL_SENDS
void AddPacket(void *xmit,void * rcv, Integer to,Integer from,Integer bytes){
comms_bytes+=2.0*bytes;
#ifdef SEND_IMMEDIATE
commtime-=usecond();
_grid->SendToRecvFrom(xmit,to,rcv,from,bytes);
commtime+=usecond();
#endif
Packet p;
p.send_buf = xmit;
p.recv_buf = rcv;
p.to_rank = to;
p.from_rank= from;
p.bytes = bytes;
p.done = 0;
comms_bytes+=2.0*bytes;
Packets.push_back(p);
}
#ifdef SERIAL_SENDS
void Communicate(void ) {
commtime-=usecond();
for(int i=0;i<Packets.size();i++){
#ifndef SEND_IMMEDIATE
_grid->SendToRecvFrom(
Packets[i].send_buf,
Packets[i].to_rank,
Packets[i].recv_buf,
Packets[i].from_rank,
Packets[i].bytes);
#endif
Packets[i].done = 1;
}
commtime+=usecond();
}
#else
void Communicate(void ) {
typedef CartesianCommunicator::CommsRequest_t CommsRequest_t;
std::vector<std::vector<CommsRequest_t> > reqs(Packets.size());
commtime-=usecond();
const int concurrency=2;
for(int i=0;i<Packets.size();i+=concurrency){
for(int ii=0;ii<concurrency;ii++){
int j = i+ii;
if ( j<Packets.size() ) {
#ifndef SEND_IMMEDIATE
_grid->SendToRecvFromBegin(reqs[j],
Packets[j].send_buf,
Packets[j].to_rank,
Packets[j].recv_buf,
Packets[j].from_rank,
Packets[j].bytes);
#endif
}
}
for(int ii=0;ii<concurrency;ii++){
int j = i+ii;
if ( j<Packets.size() ) {
#ifndef SEND_IMMEDIATE
_grid->SendToRecvFromComplete(reqs[i]);
#endif
}
}
for(int ii=0;ii<concurrency;ii++){
int j = i+ii;
if ( j<Packets.size() ) {
Packets[j].done = 1;
}
}
}
commtime+=usecond();
}
#endif
///////////////////////////////////////////
// Simd merge queue for asynch comms
///////////////////////////////////////////
struct Merge {
cobj * mpointer;
std::vector<scalar_object *> rpointers;
Integer buffer_size;
Integer packet_id;
};
std::vector<Merge> Mergers;
void AddMerge(cobj *merge_p,std::vector<scalar_object *> &rpointers,Integer buffer_size,Integer packet_id) {
Merge m;
m.mpointer = merge_p;
m.rpointers= rpointers;
m.buffer_size = buffer_size;
m.packet_id = packet_id;
#ifdef SEND_IMMEDIATE
mergetime-=usecond();
PARALLEL_FOR_LOOP
for(int o=0;o<m.buffer_size;o++){
merge1(m.mpointer[o],m.rpointers,o);
}
mergetime+=usecond();
#else
Mergers.push_back(m);
#endif
}
void CommsMerge(void ) {
//PARALLEL_NESTED_LOOP2
for(int i=0;i<Mergers.size();i++){
spintime-=usecond();
int packet_id = Mergers[i].packet_id;
while(! Packets[packet_id].done ); // spin for completion
spintime+=usecond();
#ifndef SEND_IMMEDIATE
mergetime-=usecond();
PARALLEL_FOR_LOOP
for(int o=0;o<Mergers[i].buffer_size;o++){
merge1(Mergers[i].mpointer[o],Mergers[i].rpointers,o);
}
mergetime+=usecond();
#endif
}
}
////////////////////////////////////////
// Basic Grid and stencil info
////////////////////////////////////////
int _checkerboard;
int _npoints; // Move to template param?
GridBase * _grid;
// npoints of these
std::vector<int> _directions;
std::vector<int> _distances;
std::vector<int> _comm_buf_size;
std::vector<int> _permute_type;
// npoints x Osites() of these
std::vector<std::vector<StencilEntry> > _entries;
inline StencilEntry * GetEntry(int &ptype,int point,int osite) { ptype = _permute_type[point]; return & _entries[point][osite]; }
// Comms buffers
std::vector<Vector<scalar_object> > u_simd_send_buf;
std::vector<Vector<scalar_object> > u_simd_recv_buf;
Vector<cobj> u_send_buf;
Vector<cobj> comm_buf;
int u_comm_offset;
int _unified_buffer_size;
/////////////////////////////////////////
// Timing info; ugly; possibly temporary
/////////////////////////////////////////
#define TIMING_HACK
#ifdef TIMING_HACK
double jointime;
double gathertime;
double commtime;
double halogtime;
double mergetime;
double spintime;
double comms_bytes;
double gathermtime;
double splicetime;
double nosplicetime;
#endif
CartesianStencil(GridBase *grid,
int npoints,
int checkerboard,
const std::vector<int> &directions,
const std::vector<int> &distances)
: _entries(npoints), _permute_type(npoints), _comm_buf_size(npoints)
{
#ifdef TIMING_HACK
gathertime=0;
jointime=0;
commtime=0;
halogtime=0;
mergetime=0;
spintime=0;
gathermtime=0;
splicetime=0;
nosplicetime=0;
comms_bytes=0;
#endif
_npoints = npoints;
_grid = grid;
_directions = directions;
_distances = distances;
_unified_buffer_size=0;
int osites = _grid->oSites();
for(int ii=0;ii<npoints;ii++){
int i = ii; // reverse direction to get SIMD comms done first
int point = i;
_entries[i].resize( osites);
int dimension = directions[i];
int displacement = distances[i];
int shift = displacement;
int fd = _grid->_fdimensions[dimension];
int rd = _grid->_rdimensions[dimension];
_permute_type[point]=_grid->PermuteType(dimension);
_checkerboard = checkerboard;
// the permute type
int simd_layout = _grid->_simd_layout[dimension];
int comm_dim = _grid->_processors[dimension] >1 ;
int splice_dim = _grid->_simd_layout[dimension]>1 && (comm_dim);
int sshift[2];
// Underlying approach. For each local site build
// up a table containing the npoint "neighbours" and whether they
// live in lattice or a comms buffer.
if ( !comm_dim ) {
sshift[0] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Even);
sshift[1] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Odd);
if ( sshift[0] == sshift[1] ) {
Local(point,dimension,shift,0x3);
} else {
Local(point,dimension,shift,0x1);// if checkerboard is unfavourable take two passes
Local(point,dimension,shift,0x2);// both with block stride loop iteration
}
} else { // All permute extract done in comms phase prior to Stencil application
// So tables are the same whether comm_dim or splice_dim
sshift[0] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Even);
sshift[1] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Odd);
if ( sshift[0] == sshift[1] ) {
Comms(point,dimension,shift,0x3);
} else {
Comms(point,dimension,shift,0x1);// if checkerboard is unfavourable take two passes
Comms(point,dimension,shift,0x2);// both with block stride loop iteration
}
}
}
u_send_buf.resize(_unified_buffer_size);
comm_buf.resize(_unified_buffer_size);
const int Nsimd = grid->Nsimd();
u_simd_send_buf.resize(Nsimd);
u_simd_recv_buf.resize(Nsimd);
for(int l=0;l<Nsimd;l++){
u_simd_send_buf[l].resize(_unified_buffer_size);
u_simd_recv_buf[l].resize(_unified_buffer_size);
}
}
void Local (int point, int dimension,int shiftpm,int cbmask)
{
int fd = _grid->_fdimensions[dimension];
int rd = _grid->_rdimensions[dimension];
int ld = _grid->_ldimensions[dimension];
int gd = _grid->_gdimensions[dimension];
// Map to always positive shift modulo global full dimension.
int shift = (shiftpm+fd)%fd;
// the permute type
int permute_dim =_grid->PermuteDim(dimension);
for(int x=0;x<rd;x++){
int o = 0;
int bo = x * _grid->_ostride[dimension];
int cb= (cbmask==0x2)? Odd : Even;
int sshift = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,cb);
int sx = (x+sshift)%rd;
int wraparound=0;
if ( (shiftpm==-1) && (sx>x) ) {
wraparound = 1;
}
if ( (shiftpm== 1) && (sx<x) ) {
wraparound = 1;
}
int permute_slice=0;
if(permute_dim){
int wrap = sshift/rd;
int num = sshift%rd;
if ( x< rd-num ) permute_slice=wrap;
else permute_slice = 1-wrap;
}
CopyPlane(point,dimension,x,sx,cbmask,permute_slice,wraparound);
}
}
void Comms (int point,int dimension,int shiftpm,int cbmask)
{
GridBase *grid=_grid;
const int Nsimd = grid->Nsimd();
int fd = _grid->_fdimensions[dimension];
int ld = _grid->_ldimensions[dimension];
int rd = _grid->_rdimensions[dimension];
int pd = _grid->_processors[dimension];
int simd_layout = _grid->_simd_layout[dimension];
int comm_dim = _grid->_processors[dimension] >1 ;
// assert(simd_layout==1); // Why?
assert(comm_dim==1);
int shift = (shiftpm + fd) %fd;
assert(shift>=0);
assert(shift<fd);
int buffer_size = _grid->_slice_nblock[dimension]*_grid->_slice_block[dimension]; // done in reduced dims, so SIMD factored
_comm_buf_size[point] = buffer_size; // Size of _one_ plane. Multiple planes may be gathered and
// send to one or more remote nodes.
int cb= (cbmask==0x2)? Odd : Even;
int sshift= _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,cb);
for(int x=0;x<rd;x++){
int permute_type=grid->PermuteType(dimension);
int sx = (x+sshift)%rd;
int offnode = 0;
if ( simd_layout > 1 ) {
for(int i=0;i<Nsimd;i++){
int inner_bit = (Nsimd>>(permute_type+1));
int ic= (i&inner_bit)? 1:0;
int my_coor = rd*ic + x;
int nbr_coor = my_coor+sshift;
int nbr_proc = ((nbr_coor)/ld) % pd;// relative shift in processors
if ( nbr_proc ) {
offnode =1;
}
}
} else {
int comm_proc = ((x+sshift)/rd)%pd;
offnode = (comm_proc!= 0);
}
int wraparound=0;
if ( (shiftpm==-1) && (sx>x) && (grid->_processor_coor[dimension]==0) ) {
wraparound = 1;
}
if ( (shiftpm== 1) && (sx<x) && (grid->_processor_coor[dimension]==grid->_processors[dimension]-1) ) {
wraparound = 1;
}
if (!offnode) {
int permute_slice=0;
CopyPlane(point,dimension,x,sx,cbmask,permute_slice,wraparound);
} else {
int words = buffer_size;
if (cbmask != 0x3) words=words>>1;
int rank = grid->_processor;
int recv_from_rank;
int xmit_to_rank;
int unified_buffer_offset = _unified_buffer_size;
_unified_buffer_size += words;
ScatterPlane(point,dimension,x,cbmask,unified_buffer_offset,wraparound); // permute/extract/merge is done in comms phase
}
}
}
// Routine builds up integer table for each site in _offsets, _is_local, _permute
void CopyPlane(int point, int dimension,int lplane,int rplane,int cbmask,int permute,int wrap)
{
int rd = _grid->_rdimensions[dimension];
if ( !_grid->CheckerBoarded(dimension) ) {
int o = 0; // relative offset to base within plane
int ro = rplane*_grid->_ostride[dimension]; // base offset for start of plane
int lo = lplane*_grid->_ostride[dimension]; // offset in buffer
// Simple block stride gather of SIMD objects
for(int n=0;n<_grid->_slice_nblock[dimension];n++){
for(int b=0;b<_grid->_slice_block[dimension];b++){
_entries[point][lo+o+b]._offset =ro+o+b;
_entries[point][lo+o+b]._is_local=1;
_entries[point][lo+o+b]._permute=permute;
_entries[point][lo+o+b]._around_the_world=wrap;
}
o +=_grid->_slice_stride[dimension];
}
} else {
int ro = rplane*_grid->_ostride[dimension]; // base offset for start of plane
int lo = lplane*_grid->_ostride[dimension]; // base offset for start of plane
int o = 0; // relative offset to base within plane
for(int n=0;n<_grid->_slice_nblock[dimension];n++){
for(int b=0;b<_grid->_slice_block[dimension];b++){
int ocb=1<<_grid->CheckerBoardFromOindex(o+b);
if ( ocb&cbmask ) {
_entries[point][lo+o+b]._offset =ro+o+b;
_entries[point][lo+o+b]._is_local=1;
_entries[point][lo+o+b]._permute=permute;
_entries[point][lo+o+b]._around_the_world=wrap;
}
}
o +=_grid->_slice_stride[dimension];
}
}
}
// Routine builds up integer table for each site in _offsets, _is_local, _permute
void ScatterPlane (int point,int dimension,int plane,int cbmask,int offset, int wrap)
{
int rd = _grid->_rdimensions[dimension];
if ( !_grid->CheckerBoarded(dimension) ) {
int so = plane*_grid->_ostride[dimension]; // base offset for start of plane
int o = 0; // relative offset to base within plane
int bo = 0; // offset in buffer
// Simple block stride gather of SIMD objects
for(int n=0;n<_grid->_slice_nblock[dimension];n++){
for(int b=0;b<_grid->_slice_block[dimension];b++){
_entries[point][so+o+b]._offset =offset+(bo++);
_entries[point][so+o+b]._is_local=0;
_entries[point][so+o+b]._permute=0;
_entries[point][so+o+b]._around_the_world=wrap;
}
o +=_grid->_slice_stride[dimension];
}
} else {
int so = plane*_grid->_ostride[dimension]; // base offset for start of plane
int o = 0; // relative offset to base within plane
int bo = 0; // offset in buffer
for(int n=0;n<_grid->_slice_nblock[dimension];n++){
for(int b=0;b<_grid->_slice_block[dimension];b++){
int ocb=1<<_grid->CheckerBoardFromOindex(o+b);// Could easily be a table lookup
if ( ocb & cbmask ) {
_entries[point][so+o+b]._offset =offset+(bo++);
_entries[point][so+o+b]._is_local=0;
_entries[point][so+o+b]._permute =0;
_entries[point][so+o+b]._around_the_world=wrap;
}
}
o +=_grid->_slice_stride[dimension];
}
}
}
template<class compressor>
std::thread HaloExchangeBegin(const Lattice<vobj> &source,compressor &compress) {
Mergers.resize(0);
Packets.resize(0);
HaloGather(source,compress);
return std::thread([&] { this->Communicate(); });
}
template<class compressor>
void HaloExchange(const Lattice<vobj> &source,compressor &compress)
{
auto thr = HaloExchangeBegin(source,compress);
HaloExchangeComplete(thr);
}
void HaloExchangeComplete(std::thread &thr)
{
CommsMerge(); // spins
jointime-=usecond();
thr.join();
jointime+=usecond();
}
template<class compressor>
void HaloGatherDir(const Lattice<vobj> &source,compressor &compress,int point)
{
int dimension = _directions[point];
int displacement = _distances[point];
int fd = _grid->_fdimensions[dimension];
int rd = _grid->_rdimensions[dimension];
// Map to always positive shift modulo global full dimension.
int shift = (displacement+fd)%fd;
// int checkerboard = _grid->CheckerBoardDestination(source.checkerboard,shift);
assert (source.checkerboard== _checkerboard);
// the permute type
int simd_layout = _grid->_simd_layout[dimension];
int comm_dim = _grid->_processors[dimension] >1 ;
int splice_dim = _grid->_simd_layout[dimension]>1 && (comm_dim);
// Gather phase
int sshift [2];
if ( comm_dim ) {
sshift[0] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Even);
sshift[1] = _grid->CheckerBoardShiftForCB(_checkerboard,dimension,shift,Odd);
if ( sshift[0] == sshift[1] ) {
if (splice_dim) {
splicetime-=usecond();
GatherSimd(source,dimension,shift,0x3,compress);
splicetime+=usecond();
} else {
nosplicetime-=usecond();
Gather(source,dimension,shift,0x3,compress);
nosplicetime+=usecond();
}
} else {
if(splice_dim){
splicetime-=usecond();
GatherSimd(source,dimension,shift,0x1,compress);// if checkerboard is unfavourable take two passes
GatherSimd(source,dimension,shift,0x2,compress);// both with block stride loop iteration
splicetime+=usecond();
} else {
nosplicetime-=usecond();
Gather(source,dimension,shift,0x1,compress);
Gather(source,dimension,shift,0x2,compress);
nosplicetime+=usecond();
}
}
}
}
template<class compressor>
void HaloGather(const Lattice<vobj> &source,compressor &compress)
{
// conformable(source._grid,_grid);
assert(source._grid==_grid);
halogtime-=usecond();
assert (comm_buf.size() == _unified_buffer_size );
u_comm_offset=0;
// Gather all comms buffers
for(int point = 0 ; point < _npoints; point++) {
compress.Point(point);
HaloGatherDir(source,compress,point);
}
assert(u_comm_offset==_unified_buffer_size);
halogtime+=usecond();
}
template<class compressor>
void Gather(const Lattice<vobj> &rhs,int dimension,int shift,int cbmask,compressor & compress)
{
typedef typename cobj::vector_type vector_type;
typedef typename cobj::scalar_type scalar_type;
GridBase *grid=_grid;
assert(rhs._grid==_grid);
// conformable(_grid,rhs._grid);
int fd = _grid->_fdimensions[dimension];
int rd = _grid->_rdimensions[dimension];
int pd = _grid->_processors[dimension];
int simd_layout = _grid->_simd_layout[dimension];
int comm_dim = _grid->_processors[dimension] >1 ;
assert(simd_layout==1);
assert(comm_dim==1);
assert(shift>=0);
assert(shift<fd);
int buffer_size = _grid->_slice_nblock[dimension]*_grid->_slice_block[dimension];
int cb= (cbmask==0x2)? Odd : Even;
int sshift= _grid->CheckerBoardShiftForCB(rhs.checkerboard,dimension,shift,cb);
for(int x=0;x<rd;x++){
int sx = (x+sshift)%rd;
int comm_proc = ((x+sshift)/rd)%pd;
if (comm_proc) {
int words = buffer_size;
if (cbmask != 0x3) words=words>>1;
int bytes = words * sizeof(cobj);
gathertime-=usecond();
Gather_plane_simple (rhs,u_send_buf,dimension,sx,cbmask,compress,u_comm_offset);
gathertime+=usecond();
int rank = _grid->_processor;
int recv_from_rank;
int xmit_to_rank;
_grid->ShiftedRanks(dimension,comm_proc,xmit_to_rank,recv_from_rank);
assert (xmit_to_rank != _grid->ThisRank());
assert (recv_from_rank != _grid->ThisRank());
// FIXME Implement asynchronous send & also avoid buffer copy
AddPacket((void *)&u_send_buf[u_comm_offset],
(void *) &comm_buf[u_comm_offset],
xmit_to_rank,
recv_from_rank,
bytes);
u_comm_offset+=words;
}
}
}
template<class compressor>
void GatherSimd(const Lattice<vobj> &rhs,int dimension,int shift,int cbmask,compressor &compress)
{
const int Nsimd = _grid->Nsimd();
int fd = _grid->_fdimensions[dimension];
int rd = _grid->_rdimensions[dimension];
int ld = _grid->_ldimensions[dimension];
int pd = _grid->_processors[dimension];
int simd_layout = _grid->_simd_layout[dimension];
int comm_dim = _grid->_processors[dimension] >1 ;
assert(comm_dim==1);
assert(simd_layout==2);
assert(shift>=0);
assert(shift<fd);
int permute_type=_grid->PermuteType(dimension);
///////////////////////////////////////////////
// Simd direction uses an extract/merge pair
///////////////////////////////////////////////
int buffer_size = _grid->_slice_nblock[dimension]*_grid->_slice_block[dimension];
int words = sizeof(cobj)/sizeof(vector_type);
assert(cbmask==0x3); // Fixme think there is a latent bug if not true
int bytes = buffer_size*sizeof(scalar_object);
std::vector<scalar_object *> rpointers(Nsimd);
std::vector<scalar_object *> spointers(Nsimd);
///////////////////////////////////////////
// Work out what to send where
///////////////////////////////////////////
int cb = (cbmask==0x2)? Odd : Even;
int sshift= _grid->CheckerBoardShiftForCB(rhs.checkerboard,dimension,shift,cb);
// loop over outer coord planes orthog to dim
for(int x=0;x<rd;x++){
int any_offnode = ( ((x+sshift)%fd) >= rd );
if ( any_offnode ) {
for(int i=0;i<Nsimd;i++){
spointers[i] = &u_simd_send_buf[i][u_comm_offset];
}
int sx = (x+sshift)%rd;
gathermtime-=usecond();
Gather_plane_extract<cobj>(rhs,spointers,dimension,sx,cbmask,compress);
gathermtime+=usecond();
for(int i=0;i<Nsimd;i++){
// std::cout << "GatherSimd : lane 1st elem " << i << u_simd_send_buf[i ][u_comm_offset]<<std::endl;
int inner_bit = (Nsimd>>(permute_type+1));
int ic= (i&inner_bit)? 1:0;
int my_coor = rd*ic + x;
int nbr_coor = my_coor+sshift;
int nbr_proc = ((nbr_coor)/ld) % pd;// relative shift in processors
int nbr_lcoor= (nbr_coor%ld);
int nbr_ic = (nbr_lcoor)/rd; // inner coord of peer
int nbr_ox = (nbr_lcoor%rd); // outer coord of peer
int nbr_lane = (i&(~inner_bit));
if (nbr_ic) nbr_lane|=inner_bit;
assert (sx == nbr_ox);
auto rp = &u_simd_recv_buf[i ][u_comm_offset];
auto sp = &u_simd_send_buf[nbr_lane][u_comm_offset];
void *vrp = (void *)rp;
void *vsp = (void *)sp;
if(nbr_proc){
int recv_from_rank;
int xmit_to_rank;
_grid->ShiftedRanks(dimension,nbr_proc,xmit_to_rank,recv_from_rank);
AddPacket( vsp,vrp,xmit_to_rank,recv_from_rank,bytes);
rpointers[i] = rp;
} else {
rpointers[i] = sp;
}
}
AddMerge(&comm_buf[u_comm_offset],rpointers,buffer_size,Packets.size()-1);
u_comm_offset +=buffer_size;
}
}
}
};
}
#endif
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