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Adds a parallel version of the wavelet transform (still a mockup).

Timing results suggests that it is indeed faster!
master
Joshua Moerman 11 years ago
parent
commit
2f80e92b6d
  1. 196
      wavelet/mockup.cpp

196
wavelet/mockup.cpp

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#include <includes.hpp>
#include <utilities.hpp>
#include <bsp.hpp>
#include "wavelet2.hpp"
#include "defines.hpp"
#ifndef NEXP
// will take about 1.3 GB
#define NEXP 25
#endif
const unsigned int P = 2;
const unsigned int N = 1 << NEXP;
// Static vectors for correctness checking
static std::vector<double> par_result(N);
static std::vector<double> seq_result(N);
// Convenience container of some often-used values
// NOTE: we use block distribution
// n = inputisze, p = nproc(), s = pid(), b = blocksize
struct distribution {
unsigned int n, p, s, b;
};
// fake data
static double data(unsigned int global_index){
return global_index - N/2.0 + 0.5 + std::sin(0.1337*global_index);
}
// NOTE: does not synchronize
static void read_and_distribute_data(distribution const & d, double* x){
std::vector<double> r(d.b);
for(unsigned int t = 0; t < d.p; ++t){
r.assign(d.b, 0.0);
for(unsigned int i = 0; i < d.b; ++i){
r[i] = data(i + t*d.b);
}
bsp::put(t, r.data(), x, 0, r.size());
}
}
// NOTE: we assume x, next and proczero to be already allocated and bsp::pushed
// NOTE: no sync at the end
// block distributed parallel wavelet, result is also in block distribution (in-place in x)
static void par_wavelet_base(distribution const & d, double* x, double* next, double* proczero){
for(unsigned int i = 1; i <= d.b/4; i <<= 1){
// send the two elements over
auto t = (d.s - 1 + d.p) % d.p;
bsp::put(t, &x[0], next, 0);
bsp::put(t, &x[i], next, 1);
bsp::sync();
wvlt::wavelet_mul(x, next[0], next[1], d.b, i);
}
// fan in (i.e. 2 elements to proc zero)
bsp::sync();
// send 2 of your own elements
for(unsigned int i = 0; i < 2; ++i){
bsp::put(0, &x[i * d.b/2], proczero, d.s * 2 + i);
}
bsp::sync();
// proc zero has the privilige/duty to finish the job
if(d.s == 0) {
wvlt::wavelet(proczero, 2*d.p);
// and to send it back to everyone
for(unsigned int t = 0; t < d.p; ++t){
for(unsigned int i = 0; i < 2; ++i){
bsp::put(t, &proczero[t*2 + i], x, i * d.b/2);
}
}
}
}
static void par_wavelet(){
bsp::begin(P);
distribution d{N, bsp::nprocs(), bsp::pid(), N/P};
// We allocate and push everything up front, since we need it anyways
// (so peak memory is the same). This saves us 1 bsp::sync
// For convenience and consistency we use std::vector
std::vector<double> x(d.b, 0.0);
std::vector<double> next(2, 0.0);
std::vector<double> proczero(d.s == 0 ? 2*d.p : 1, 0.0);
bsp::push_reg(x.data(), x.size());
bsp::push_reg(next.data(), next.size());
bsp::push_reg(proczero.data(), proczero.size());
bsp::sync();
// processor zero reads data from file
// gives each proc its own piece
if(d.s == 0) read_and_distribute_data(d, x.data());
bsp::sync();
double time1 = bsp::time();
par_wavelet_base(d, x.data(), next.data(), proczero.data());
bsp::sync();
double time2 = bsp::time();
if(d.s==0) printf("parallel version\t%f\n", time2 - time1);
// Clean up and send all data to proc zero for correctness checking
// So this is not part of the parallel program anymore
bsp::pop_reg(proczero.data());
bsp::pop_reg(next.data());
next.clear();
proczero.clear();
bsp::push_reg(par_result.data(), par_result.size());
bsp::sync();
bsp::put(0, x.data(), par_result.data(), d.s * d.b, d.b);
bsp::sync();
bsp::pop_reg(par_result.data());
bsp::pop_reg(x.data());
bsp::end();
}
static void seq_wavelet(){
std::vector<double> v(N);
for(unsigned int i = 0; i < N; ++i) v[i] = data(i);
{ auto time1 = timer::clock::now();
wvlt::wavelet(v.data(), v.size());
auto time2 = timer::clock::now();
printf("sequential version\t%f\n", timer::from_dur(time2 - time1));
}
std::copy(v.begin(), v.end(), seq_result.begin());
}
// Checks whether seq and par agree
// NOTE: modifies the global par_result
static void check_equality(double threshold){
if(par_result == seq_result){
std::cout << colors::green("SUCCES:") << " Results are bitwise equal" << std::endl;
} else {
for(unsigned int i = 0; i < N; ++i){
auto sq = par_result[i] - seq_result[i];
par_result[i] = sq*sq;
}
auto rmse = std::sqrt(std::accumulate(par_result.begin(), par_result.end(), 0.0) / N);
if(rmse <= threshold){
std::cout << colors::green("SUCCES:") << " Results are almost the same: rmse = " << rmse << std::endl;
} else {
std::cout << colors::red("FAIL:") << " Results differ: rmse = " << rmse << std::endl;
}
}
}
// Checks whether inverse gives us the data back
// NOTE: modifies the global seq_result
static void check_inverse(double threshold){
wvlt::unwavelet(seq_result.data(), seq_result.size());
bool same = true;
for(unsigned int i = 0; i < N; ++i){
if(data(i) != seq_result[i]) same = false;
auto sq = data(i) - seq_result[i];
seq_result[i] = sq*sq;
}
auto rmse = std::sqrt(std::accumulate(seq_result.begin(), seq_result.end(), 0.0) / N);
if(same){
std::cout << colors::green("SUCCES:") << " Inverse is bitwise correct" << std::endl;
} else {
if(rmse <= threshold){
std::cout << colors::green("SUCCES:") << " Inverse are almost correct: rmse = " << rmse << std::endl;
} else {
std::cout << colors::red("FAIL:") << " Inverse seems wrong: rmse = " << rmse << std::endl;
}
}
}
int main(int argc, char** argv){
bsp::init(par_wavelet, argc, argv);
// Run both versions (will print timings)
seq_wavelet();
par_wavelet();
// Checking equality of algorithms
bool should_check = false;
if(should_check){
double threshold = 1.0e-8;
check_equality(threshold);
check_inverse(threshold);
}
}