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Reimplemented precisionChange to run on GPUs. A workspace containing the mapping table can be optionally precomputed and reused for improved performance.

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This commit is contained in:
Christopher Kelly 2021-01-06 09:30:49 -05:00
parent d185f2eaa7
commit d7a2a4852d
1 changed files with 99 additions and 37 deletions
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136
Grid/lattice/Lattice_transfer.h
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@ -998,54 +998,116 @@ vectorizeFromRevLexOrdArray( std::vector<sobj> &in, Lattice<vobj> &out)
});
}
//Convert a Lattice from one precision to another
template<class VobjOut, class VobjIn>
void precisionChange(Lattice<VobjOut> &out, const Lattice<VobjIn> &in)
{
assert(out.Grid()->Nd() == in.Grid()->Nd());
for(int d=0;d<out.Grid()->Nd();d++){
assert(out.Grid()->FullDimensions()[d] == in.Grid()->FullDimensions()[d]);
//The workspace for a precision change operation allowing for the reuse of the mapping to save time on subsequent calls
class precisionChangeWorkspace{
std::pair<Integer,Integer>* fmap_device; //device pointer
public:
precisionChangeWorkspace(GridBase *out_grid, GridBase *in_grid){
//Build a map between the sites and lanes of the output field and the input field as we cannot use the Grids on the device
assert(out_grid->Nd() == in_grid->Nd());
for(int d=0;d<out_grid->Nd();d++){
assert(out_grid->FullDimensions()[d] == in_grid->FullDimensions()[d]);
}
int Nsimd_out = out_grid->Nsimd();
std::vector<Coordinate> out_icorrs(out_grid->Nsimd()); //reuse these
for(int lane=0; lane < out_grid->Nsimd(); lane++)
out_grid->iCoorFromIindex(out_icorrs[lane], lane);
std::vector<std::pair<Integer,Integer> > fmap_host(out_grid->lSites()); //lsites = osites*Nsimd
thread_for(out_oidx,out_grid->oSites(),{
Coordinate out_ocorr;
out_grid->oCoorFromOindex(out_ocorr, out_oidx);
Coordinate lcorr; //the local coordinate (common to both in and out as full coordinate)
for(int out_lane=0; out_lane < Nsimd_out; out_lane++){
out_grid->InOutCoorToLocalCoor(out_ocorr, out_icorrs[out_lane], lcorr);
//int in_oidx = in_grid->oIndex(lcorr), in_lane = in_grid->iIndex(lcorr);
//Note oIndex and OcorrFromOindex (and same for iIndex) are not inverse for checkerboarded lattice, the former coordinates being defined on the full lattice and the latter on the reduced lattice
//Until this is fixed we need to circumvent the problem locally. Here I will use the coordinates defined on the reduced lattice for simplicity
int in_oidx = 0, in_lane = 0;
for(int d=0;d<in_grid->_ndimension;d++){
in_oidx += in_grid->_ostride[d] * ( lcorr[d] % in_grid->_rdimensions[d] );
in_lane += in_grid->_istride[d] * ( lcorr[d] / in_grid->_rdimensions[d] );
}
fmap_host[out_lane + Nsimd_out*out_oidx] = std::pair<Integer,Integer>( in_oidx, in_lane );
}
});
//Copy the map to the device (if we had a way to tell if an accelerator is in use we could avoid this copy for CPU-only machines)
size_t fmap_bytes = out_grid->lSites() * sizeof(std::pair<Integer,Integer>);
fmap_device = (std::pair<Integer,Integer>*)acceleratorAllocDevice(fmap_bytes);
acceleratorCopyToDevice(fmap_host.data(), fmap_device, fmap_bytes);
}
//Prevent moving or copying
precisionChangeWorkspace(const precisionChangeWorkspace &r) = delete;
precisionChangeWorkspace(precisionChangeWorkspace &&r) = delete;
precisionChangeWorkspace &operator=(const precisionChangeWorkspace &r) = delete;
precisionChangeWorkspace &operator=(precisionChangeWorkspace &&r) = delete;
std::pair<Integer,Integer> const* getMap() const{ return fmap_device; }
~precisionChangeWorkspace(){
acceleratorFreeDevice(fmap_device);
}
};
//Convert a lattice of one precision to another. The input workspace contains the mapping data.
template<class VobjOut, class VobjIn>
void precisionChange(Lattice<VobjOut> &out, const Lattice<VobjIn> &in, const precisionChangeWorkspace &workspace){
out.Checkerboard() = in.Checkerboard();
GridBase *in_grid=in.Grid();
GridBase *out_grid = out.Grid();
typedef typename VobjOut::scalar_object SobjOut;
typedef typename VobjIn::scalar_object SobjIn;
int ndim = out.Grid()->Nd();
int out_nsimd = out_grid->Nsimd();
std::vector<Coordinate > out_icoor(out_nsimd);
for(int lane=0; lane < out_nsimd; lane++){
out_icoor[lane].resize(ndim);
out_grid->iCoorFromIindex(out_icoor[lane], lane);
}
std::vector<SobjOut> in_slex_conv(in_grid->lSites());
unvectorizeToLexOrdArray(in_slex_conv, in);
autoView( out_v , out, CpuWrite);
thread_for(out_oidx,out_grid->oSites(),{
Coordinate out_ocoor(ndim);
out_grid->oCoorFromOindex(out_ocoor, out_oidx);
typedef typename SobjIn::scalar_type SfundIn; //"fundamental" complex/real data types
typedef typename SobjOut::scalar_type SfundOut;
ExtractPointerArray<SobjOut> ptrs(out_nsimd);
constexpr int Nsimd_out = VobjOut::Nsimd();
constexpr int Nfund_in = sizeof(SobjIn)/sizeof(SfundIn);
constexpr int Nfund_out = sizeof(SobjOut)/sizeof(SfundOut); //these should be the same!
Coordinate lcoor(out_grid->Nd());
for(int lane=0; lane < out_nsimd; lane++){
for(int mu=0;mu<ndim;mu++)
lcoor[mu] = out_ocoor[mu] + out_grid->_rdimensions[mu]*out_icoor[lane][mu];
static_assert(Nfund_in == Nfund_out, "Expect input and output object types to contain the same number of fundamental data but with different precision!");
std::pair<Integer,Integer> const* fmap_device = workspace.getMap();
//Do the copy/precision change
autoView( out_v , out, AcceleratorWrite);
autoView( in_v , in, AcceleratorRead);
accelerator_for(out_oidx, out.Grid()->oSites(), 1,{
std::pair<Integer,Integer> const* fmap_osite = fmap_device + out_oidx*Nsimd_out;
for(int out_lane=0; out_lane < Nsimd_out; out_lane++){
int in_oidx = fmap_osite[out_lane].first;
int in_lane = fmap_osite[out_lane].second;
int llex; Lexicographic::IndexFromCoor(lcoor, llex, out_grid->_ldimensions);
ptrs[lane] = &in_slex_conv[llex];
}
merge(out_v[out_oidx], ptrs, 0);
});
//Room for optimization here by combining the precision change with the read/write to avoid the intermediate scalar objects
SobjIn sobj_in = extractLane(in_lane, in_v[in_oidx]);
SobjOut sobj_out;
SfundIn tmp_in;
SfundOut tmp_out;
for(int i=0;i<Nfund_out;i++){ //the blessed way to do type punning!
memcpy( (char*)(&tmp_in), (char*)(&sobj_in) + i*sizeof(SfundIn), sizeof(SfundIn) );
tmp_out = tmp_in; //the precision change
memcpy( (char*)(&sobj_out) + i*sizeof(SfundOut), (char*)(&tmp_out), sizeof(SfundOut) );
}
insertLane(out_lane, out_v[out_oidx], sobj_out);
}
});
}
//Convert a Lattice from one precision to another
//Generate the workspace in place; if multiple calls with the same mapping are performed, consider pregenerating the workspace and reusing
template<class VobjOut, class VobjIn>
void precisionChange(Lattice<VobjOut> &out, const Lattice<VobjIn> &in){
precisionChangeWorkspace workspace(out.Grid(), in.Grid());
precisionChange(out, in, workspace);
}
////////////////////////////////////////////////////////////////////////////////
// Communicate between grids
////////////////////////////////////////////////////////////////////////////////