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92 lines
1.9 KiB
C++
92 lines
1.9 KiB
C++
/*
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* Waksman.cpp
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*
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*/
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#include "Waksman.h"
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#include <algorithm>
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#include <assert.h>
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#include <math.h>
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template<class T>
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void append(vector<T>& x, const vector<T>& y)
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{
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x.insert(x.end(), y.begin(), y.end());
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}
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vector<vector<bool> > Waksman::configure(const vector<int>& perm)
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{
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int n = perm.size();
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assert(n > 1);
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if (n == 2)
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return {{perm[0] == 1, perm[0] == 1}};
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vector<bool> I(n / 2);
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vector<char> O(n / 2, -1);
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vector<int> p0(n / 2, -1), p1(n / 2, -1), inv_perm(n);
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for (int i = 0; i < n; i++)
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inv_perm[perm[i]] = i;
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while (true)
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{
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auto it = find(O.begin(), O.end(), -1);
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if (it == O.end())
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break;
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int j = 2 * (it - O.begin());
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O.at(j / 2) = 0;
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int j0 = j;
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while (true)
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{
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int i = inv_perm.at(j);
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p0.at(i / 2) = j / 2;
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I.at(i / 2) = i % 2;
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O.at(j / 2) = j % 2;
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if (i % 2 == 1)
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i--;
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else
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i++;
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j = perm.at(i);
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if (j % 2 == 1)
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j--;
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else
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j++;
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p1.at(i / 2) = perm.at(i) / 2;
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if (j == j0)
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break;
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}
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if ((find(p1.begin(), p1.end(), -1) == p1.end())
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and (find(p0.begin(), p0.end(), -1) == p0.end()))
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break;
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}
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auto p0_config = configure(p0);
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auto p1_config = configure(p1);
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vector<vector<bool>> res;
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res.push_back(I);
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for (auto& x : O)
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res.back().push_back(x);
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assert(p0_config.size() == p1_config.size());
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for (size_t i = 0; i < p0_config.size(); i++)
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{
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res.push_back(p0_config.at(i));
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append(res.back(), p1_config.at(i));
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}
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assert(res.size() == Waksman(perm.size()).n_rounds());
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return res;
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}
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Waksman::Waksman(int n_elements) :
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n_elements(n_elements), nr(log2(n_elements))
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{
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assert(n_elements == (1 << nr));
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}
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