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86 lines
2.5 KiB
86 lines
2.5 KiB
#pragma once
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#include <includes.hpp>
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#include <utilities.hpp>
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#include <bsp.hpp>
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#include "wavelet.hpp"
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/* In the following function we assume any in-parameter to be already
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* bsp::pushed. And the functions won't do any bsp::sync at the end. Both
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* conventions make it possible to chains functions with lesser syncs.
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*
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* Distribution is block distribution.
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*/
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namespace wvlt {
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namespace par {
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// Convenience container of some often-used values
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// n = inputisze, p = nproc(), s = pid()
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// b = blocksize, prev/next = previous and next processor index
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struct distribution {
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unsigned int n, p, s, b, prev, next;
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distribution(unsigned int n_, unsigned int p_, unsigned int s_)
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: n(n_), p(p_), s(s_), b(n/p), prev((s-1+p)%p), next((s+1)%p)
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{}
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};
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inline unsigned int communication_size(unsigned int m){
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return pow_two(m+1) - 2;
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}
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inline void step(distribution const & d, double* x, double* other, unsigned int size, unsigned int stride, unsigned int m){
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unsigned int t = d.prev;
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unsigned int Cm = communication_size(m);
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for(unsigned int i = 0; i < Cm; ++i){
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bsp::put(t, &x[stride*i], other, i, 1);
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}
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bsp::sync();
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unsigned int end = pow_two(m);
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for(unsigned int i = 1; i < end; i <<= 1){
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wavelet_mul(x, other[0], other[i], size, stride*i);
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if(i < end/2) wavelet_mul_base(other, 2*end - 2*i, i);
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}
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}
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inline void base(distribution const & d, double* x, double* other, unsigned int size, unsigned int m){
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unsigned int t = two_log(d.b);
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unsigned int steps = (t-1)/m;
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unsigned int stride = 1;
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for(unsigned int i = steps; i; i--){
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step(d, x, other, size, stride, m);
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stride <<= m;
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}
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unsigned int remaining = (t-1) - m*steps;
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if(remaining)
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step(d, x, other, size, stride, remaining);
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}
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// block distributed parallel wavelet, result is also in block distribution (in-place in x)
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inline void wavelet(distribution const & d, double* x, double* next, double* proczero, unsigned int m){
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// First do the local part
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base(d, x, next, d.b, m);
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// Then do a fan in (i.e. 2 elements to proc zero)
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for(unsigned int i = 0; i < 2; ++i){
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bsp::put(0, &x[i * d.b/2], proczero, d.s * 2 + i);
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}
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bsp::sync();
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// proc zero has the privilige/duty to finish the job
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if(d.s == 0) {
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wvlt::wavelet(proczero, 2*d.p, 1);
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// and to send it back to everyone
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for(unsigned int t = 0; t < d.p; ++t){
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for(unsigned int i = 0; i < 2; ++i){
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bsp::put(t, &proczero[t*2 + i], x, i * d.b/2);
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}
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}
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}
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}
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}
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}
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