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Faster halo exchange

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This commit is contained in:
Peter Boyle 2023-10-19 18:16:47 -04:00
parent e064f17346
commit 5fac47a26d
1 changed files with 60 additions and 34 deletions
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94
Grid/lattice/PaddedCell.h
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@ -47,16 +47,15 @@ struct CshiftImplGauge: public CshiftImplBase<typename Gimpl::GaugeLinkField::ve
template<class vobj> inline void ScatterSlice(const cshiftVector<typename vobj::scalar_object> &buf,
template<class vobj> inline void ScatterSlice(const cshiftVector<vobj> &buf,
Lattice<vobj> &lat,
int x,
int dim,
int offset=0)
{
const int Nsimd=vobj::Nsimd();
typedef typename vobj::scalar_object sobj;
autoView(lat_v, lat, AcceleratorRead);
GridBase *grid = lat.Grid();
Coordinate simd = grid->_simd_layout;
int Nd = grid->Nd();
@ -73,7 +72,8 @@ template<class vobj> inline void ScatterSlice(const cshiftVector<typename vobj::
Coordinate rsimd= simd; rsimd[dim]=1; // maybe reduce Nsimd
int rNsimd = 1; for(int d=0;d<Nd;d++) rNsimd*=rsimd[d];
int rNsimda= Nsimd/simd[dim]; // should be equal
assert(rNsimda==rNsimd);
int face_ovol=block*nblock;
// assert(buf.size()==face_ovol*rNsimd);
@ -82,22 +82,26 @@ template<class vobj> inline void ScatterSlice(const cshiftVector<typename vobj::
//Let's make it work on GPU and then make a special accelerator_for that
//doesn't hide the SIMD direction and keeps explicit in the threadIdx
//for cross platform
// FIXME -- can put internal indices into thread loop
auto buf_p = & buf[0];
accelerator_for(ss, face_ovol,rNsimd,{
autoView(lat_v, lat, AcceleratorRead);
accelerator_for(ss, face_ovol/simd[dim],Nsimd,{
// scalar layout won't coalesce
int olane=acceleratorSIMTlane(rNsimd);
sobj obj = buf_p[ss+olane*face_ovol+offset];
int blane=acceleratorSIMTlane(Nsimd); // buffer lane
int olane=blane%rNsimd; // reduced lattice lane
int obit =blane/rNsimd;
////////////////////////////////////////////
// osite
////////////////////////////////////////////
int b = ss%block;
int n = ss/block;
///////////////////////////////////////////////////////////////
// osite -- potentially one bit from simd in the buffer: (ss<<1)|obit
///////////////////////////////////////////////////////////////
int ssp = ss*simd[dim]+obit;
int b = ssp%block;
int n = ssp/block;
int osite= b+n*stride + ox*block;
////////////////////////////////////////////
// isite
// isite -- map lane within buffer to lane within lattice
////////////////////////////////////////////
Coordinate icoor;
int lane;
@ -108,16 +112,18 @@ template<class vobj> inline void ScatterSlice(const cshiftVector<typename vobj::
///////////////////////////////////////////
// Transfer into lattice - will coalesce
///////////////////////////////////////////
sobj obj = extractLane(blane,buf_p[ss+offset]);
insertLane(lane,lat_v[osite],obj);
});
}
template<class vobj> inline void GatherSlice(cshiftVector<typename vobj::scalar_object> &buf,
template<class vobj> inline void GatherSlice(cshiftVector<vobj> &buf,
const Lattice<vobj> &lat,
int x,
int dim,
int offset=0)
{
const int Nsimd=vobj::Nsimd();
typedef typename vobj::scalar_object sobj;
autoView(lat_v, lat, AcceleratorRead);
@ -149,20 +155,29 @@ template<class vobj> inline void GatherSlice(cshiftVector<typename vobj::scalar_
//for cross platform
//For CPU perhaps just run a loop over Nsimd
auto buf_p = & buf[0];
accelerator_for(ss, face_ovol,rNsimd,{
std::cout << " simd["<<dim<<"] "<< simd[dim] <<std::endl;
std::cout << " simd "<< simd <<std::endl;
std::cout << " Nsimd "<< Nsimd <<std::endl;
std::cout << " rNsimd "<< rNsimd <<std::endl;
accelerator_for(ss, face_ovol/simd[dim],Nsimd,{
// scalar layout won't coalesce
int blane=acceleratorSIMTlane(Nsimd); // buffer lane
int olane=blane%rNsimd; // reduced lattice lane
int obit =blane/rNsimd;
////////////////////////////////////////////
// osite
////////////////////////////////////////////
int b = ss%block;
int n = ss/block;
int ssp = ss*simd[dim]+obit;
int b = ssp%block;
int n = ssp/block;
int osite= b+n*stride + ox*block;
////////////////////////////////////////////
// isite
// isite -- map lane within buffer to lane within lattice
////////////////////////////////////////////
Coordinate icoor;
int olane=acceleratorSIMTlane(rNsimd);
int lane;
Lexicographic::CoorFromIndex(icoor,olane,rsimd);
icoor[dim]=ix;
@ -171,10 +186,23 @@ template<class vobj> inline void GatherSlice(cshiftVector<typename vobj::scalar_
///////////////////////////////////////////
// Take out of lattice
///////////////////////////////////////////
sobj obj = extractLane(lane,lat_v[osite]);
buf_p[ss+olane*face_ovol+offset] = obj;
insertLane(blane,buf_p[ss+offset],obj);
});
/*
int words =block*nblock/simd[dim];
std::vector<vobj> tbuf(words);
acceleratorCopyFromDevice((void *)&buf[offset],(void *)&tbuf[0],words*sizeof(vobj));
typedef typename vobj::scalar_type scalar;
scalar *sbuf = (scalar *)&tbuf[0];
scalar tmp=0.0;
for(int w=0;w<words*sizeof(vobj)/sizeof(scalar);w++){
tmp=tmp+conjugate(sbuf[w])*sbuf[w];
}
std::cout << " Gathered buffer norm "<<tmp<<std::endl;
*/
}
@ -260,13 +288,13 @@ public:
return tmp;
}
template<class vobj>
inline Lattice<vobj> ExchangeTest(const Lattice<vobj> &in, const CshiftImplBase<vobj> &cshift = CshiftImplDefault<vobj>()) const
inline Lattice<vobj> ExchangePeriodic(const Lattice<vobj> &in, const CshiftImplBase<vobj> &cshift = CshiftImplDefault<vobj>()) const
{
GridBase *old_grid = in.Grid();
int dims = old_grid->Nd();
Lattice<vobj> tmp = in;
for(int d=0;d<dims;d++){
tmp = ExpandTest(d,tmp,cshift); // rvalue && assignment
tmp = ExpandPeriodic(d,tmp,cshift); // rvalue && assignment
}
return tmp;
}
@ -337,9 +365,6 @@ public:
InsertSliceLocal(shifted,padded,x,x,dim);
}
tins += usecond() - t;
// std::cout << GridLogMessage << "dimension " <<dim<<std::endl;
// DumpSliceNorm(std::string("Old_exchange from"),in,dim);
// DumpSliceNorm(std::string("Old_exchange to "),padded,dim);
}
std::cout << GridLogPerformance << "PaddedCell::Expand timings: cshift:" << tshift/1000 << "ms, insert-slice:" << tins/1000 << "ms" << std::endl;
@ -348,7 +373,7 @@ public:
}
template<class vobj>
inline Lattice<vobj> ExpandTest(int dim, const Lattice<vobj> &in, const CshiftImplBase<vobj> &cshift = CshiftImplDefault<vobj>()) const
inline Lattice<vobj> ExpandPeriodic(int dim, const Lattice<vobj> &in, const CshiftImplBase<vobj> &cshift = CshiftImplDefault<vobj>()) const
{
Coordinate processors=unpadded_grid->_processors;
GridBase *old_grid = in.Grid();
@ -412,7 +437,7 @@ public:
Coordinate simd= from.Grid()->_simd_layout;
int ld = lds[dimension];
int nld = to.Grid()->_ldimensions[dimension];
const int Nsimd = vobj::Nsimd();
assert(depth<=lds[dimension]); // A must be on neighbouring node
assert(depth>0); // A caller bug if zero
@ -424,16 +449,17 @@ public:
for(int d=0;d<lds.size();d++){
if ( d!= dimension) buffer_size=buffer_size*lds[d];
}
int rNsimd = vobj::Nsimd() / simd[dimension];
assert( buffer_size == from.Grid()->_slice_nblock[dimension]*from.Grid()->_slice_block[dimension] *rNsimd);
buffer_size = buffer_size / Nsimd;
int rNsimd = Nsimd / simd[dimension];
assert( buffer_size == from.Grid()->_slice_nblock[dimension]*from.Grid()->_slice_block[dimension] / simd[dimension]);
static cshiftVector<sobj> send_buf;
static cshiftVector<sobj> recv_buf;
static cshiftVector<vobj> send_buf;
static cshiftVector<vobj> recv_buf;
send_buf.resize(buffer_size*2*depth);
recv_buf.resize(buffer_size*2*depth);
int words = buffer_size;
int bytes = words * sizeof(sobj);
int bytes = words * sizeof(vobj);
////////////////////////////////////////////////////////////////////////////
// Gather all surface terms up to depth "d"
////////////////////////////////////////////////////////////////////////////
@ -491,14 +517,14 @@ public:
ScatterSlice(recv_buf,to,nld-depth+d,dimension,plane*buffer_size); plane++;
}
t_scatter= usecond() - t;
// DumpSliceNorm(std::string("Face_exchange to done"),to,dimension);
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: gather :" << t_gather/1000 << "ms"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: scatter:" << t_scatter/1000 << "ms"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: gather :" << 2.0*bytes/t_gather << "MB/s"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: scatter:" << t_scatter/1000 << "ms"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: scatter:" << 2.0*bytes/t_scatter<< "MB/s"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: copy :" << t_copy/1000 << "ms"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: comms :" << t_comms/1000 << "ms"<<std::endl;
std::cout << GridLogPerformance << "PaddedCell::Expand new timings: comms :" << (RealD)4.0*bytes/t_comms << "MB/s"<<std::endl;
// DumpSliceNorm(std::string("Face_exchange to done"),to,dimension);
}
};