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more FFT optimisations

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This commit is contained in:
Antonin Portelli
2016-10-26 17:36:26 +01:00
parent 33d199a0ad
commit 14ddf2c234
2 changed files with 121 additions and 136 deletions
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233
lib/FFT.h
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@ -98,174 +98,157 @@ namespace Grid {
#define FFTW_BACKWARD (+1)
#endif
class FFT {
class FFT {
private:
GridCartesian *vgrid;
GridCartesian *sgrid;
int Nd;
double flops;
double flops_call;
uint64_t usec;
std::vector<int> dimensions;
std::vector<int> processors;
std::vector<int> processor_coor;
public:
static const int forward=FFTW_FORWARD;
static const int backward=FFTW_BACKWARD;
double Flops(void) {return flops;}
double MFlops(void) {return flops/usec;}
FFT ( GridCartesian * grid ) :
vgrid(grid),
Nd(grid->_ndimension),
dimensions(grid->_fdimensions),
processors(grid->_processors),
processor_coor(grid->_processor_coor)
FFT ( GridCartesian * grid ) :
vgrid(grid),
Nd(grid->_ndimension),
dimensions(grid->_fdimensions),
processors(grid->_processors),
processor_coor(grid->_processor_coor)
{
flops=0;
usec =0;
std::vector<int> layout(Nd,1);
sgrid = new GridCartesian(dimensions,layout,processors);
};
~FFT ( void) {
delete sgrid;
~FFT ( void) {
delete sgrid;
}
template<class vobj>
void FFT_dim(Lattice<vobj> &result,const Lattice<vobj> &source,int dim, int inverse){
#ifndef HAVE_FFTW
assert(0);
#else
conformable(result._grid,vgrid);
conformable(source._grid,vgrid);
int L = vgrid->_ldimensions[dim];
int G = vgrid->_fdimensions[dim];
std::vector<int> layout(Nd,1);
std::vector<int> pencil_gd(vgrid->_fdimensions);
pencil_gd[dim] = G*processors[dim];
pencil_gd[dim] = G*processors[dim];
// Pencil global vol LxLxGxLxL per node
GridCartesian pencil_g(pencil_gd,layout,processors);
// Construct pencils
typedef typename vobj::scalar_object sobj;
typedef typename sobj::scalar_type scalar;
Lattice<sobj> pgbuf(&pencil_g);
Lattice<vobj> ssource(vgrid); ssource =source;
Lattice<sobj> pgsource(&pencil_g);
Lattice<sobj> pgresult(&pencil_g); pgresult=zero;
#ifndef HAVE_FFTW
assert(0);
#else
typedef typename FFTW<scalar>::FFTW_scalar FFTW_scalar;
typedef typename FFTW<scalar>::FFTW_plan FFTW_plan;
{
int Ncomp = sizeof(sobj)/sizeof(scalar);
int Nlow = 1;
for(int d=0;d<dim;d++){
Nlow*=vgrid->_ldimensions[d];
}
int rank = 1; /* 1d transforms */
int n[] = {G}; /* 1d transforms of length G */
int howmany = Ncomp;
int odist,idist,istride,ostride;
idist = odist = 1; /* Distance between consecutive FT's */
istride = ostride = Ncomp*Nlow; /* distance between two elements in the same FT */
int *inembed = n, *onembed = n;
int sign = FFTW_FORWARD;
if (inverse) sign = FFTW_BACKWARD;
FFTW_plan p;
{
FFTW_scalar *in = (FFTW_scalar *)&pgsource._odata[0];
FFTW_scalar *out= (FFTW_scalar *)&pgresult._odata[0];
p = FFTW<scalar>::fftw_plan_many_dft(rank,n,howmany,
in,inembed,
istride,idist,
out,onembed,
ostride, odist,
sign,FFTW_ESTIMATE);
}
std::vector<int> lcoor(Nd), gcoor(Nd);
// Barrel shift and collect global pencil
for(int p=0;p<processors[dim];p++) {
for(int idx=0;idx<sgrid->lSites();idx++) {
sgrid->LocalIndexToLocalCoor(idx,lcoor);
sobj s;
peekLocalSite(s,ssource,lcoor);
lcoor[dim]+=p*L;
pokeLocalSite(s,pgsource,lcoor);
}
ssource = Cshift(ssource,dim,L);
}
// Loop over orthog coords
int NN=pencil_g.lSites();
GridStopWatch timer;
timer.Start();
//PARALLEL_FOR_LOOP
for(int idx=0;idx<NN;idx++) {
pencil_g.LocalIndexToLocalCoor(idx,lcoor);
if ( lcoor[dim] == 0 ) { // restricts loop to plane at lcoor[dim]==0
FFTW_scalar *in = (FFTW_scalar *)&pgsource._odata[idx];
FFTW_scalar *out= (FFTW_scalar *)&pgresult._odata[idx];
FFTW<scalar>::fftw_execute_dft(p,in,out);
}
}
timer.Stop();
double add,mul,fma;
FFTW<scalar>::fftw_flops(p,&add,&mul,&fma);
flops_call = add+mul+2.0*fma;
usec += timer.useconds();
flops+= flops_call*NN;
int pc = processor_coor[dim];
for(int idx=0;idx<sgrid->lSites();idx++) {
sgrid->LocalIndexToLocalCoor(idx,lcoor);
gcoor = lcoor;
// extract the result
sobj s;
gcoor[dim] = lcoor[dim]+L*pc;
peekLocalSite(s,pgresult,gcoor);
pokeLocalSite(s,result,lcoor);
}
FFTW<scalar>::fftw_destroy_plan(p);
int Ncomp = sizeof(sobj)/sizeof(scalar);
int Nlow = 1;
for(int d=0;d<dim;d++){
Nlow*=vgrid->_ldimensions[d];
}
int rank = 1; /* 1d transforms */
int n[] = {G}; /* 1d transforms of length G */
int howmany = Ncomp;
int odist,idist,istride,ostride;
idist = odist = 1; /* Distance between consecutive FT's */
istride = ostride = Ncomp*Nlow; /* distance between two elements in the same FT */
int *inembed = n, *onembed = n;
int sign = FFTW_FORWARD;
if (inverse) sign = FFTW_BACKWARD;
FFTW_plan p;
{
FFTW_scalar *in = (FFTW_scalar *)&pgbuf._odata[0];
FFTW_scalar *out= (FFTW_scalar *)&pgbuf._odata[0];
p = FFTW<scalar>::fftw_plan_many_dft(rank,n,howmany,
in,inembed,
istride,idist,
out,onembed,
ostride, odist,
sign,FFTW_ESTIMATE);
}
// Barrel shift and collect global pencil
std::vector<int> lcoor(Nd), gcoor(Nd);
result = source;
for(int p=0;p<processors[dim];p++) {
for(int idx=0;idx<sgrid->lSites();idx++) {
sgrid->LocalIndexToLocalCoor(idx,lcoor);
sobj s;
peekLocalSite(s,result,lcoor);
lcoor[dim]+=p*L;
pokeLocalSite(s,pgbuf,lcoor);
}
result = Cshift(result,dim,L);
}
// Loop over orthog coords
int NN=pencil_g.lSites();
GridStopWatch timer;
timer.Start();
//PARALLEL_FOR_LOOP
for(int idx=0;idx<NN;idx++) {
pencil_g.LocalIndexToLocalCoor(idx,lcoor);
if ( lcoor[dim] == 0 ) { // restricts loop to plane at lcoor[dim]==0
FFTW_scalar *in = (FFTW_scalar *)&pgbuf._odata[idx];
FFTW_scalar *out= (FFTW_scalar *)&pgbuf._odata[idx];
FFTW<scalar>::fftw_execute_dft(p,in,out);
}
}
timer.Stop();
// performance counting
double add,mul,fma;
FFTW<scalar>::fftw_flops(p,&add,&mul,&fma);
flops_call = add+mul+2.0*fma;
usec += timer.useconds();
flops+= flops_call*NN;
// writing out result
int pc = processor_coor[dim];
for(int idx=0;idx<sgrid->lSites();idx++) {
sgrid->LocalIndexToLocalCoor(idx,lcoor);
gcoor = lcoor;
sobj s;
gcoor[dim] = lcoor[dim]+L*pc;
peekLocalSite(s,pgbuf,gcoor);
pokeLocalSite(s,result,lcoor);
}
// destroying plan
FFTW<scalar>::fftw_destroy_plan(p);
#endif
}
};
}
#endif