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root_node_processing.cpp
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root_node_processing.cpp
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#include "bitset.h"
#include "sequential_solver.h"
#include "graph.h"
#include "util.h"
#include <algorithm>
#include <thread>
#include <vector>
vector<int> initialise(const SparseGraph & g) {
// printf("Starting init\n");
vector<int> vv;
if (!g.n)
return vv;
vector<int> residual_degs;
residual_degs.reserve(g.n);
for (auto & lst : g.adjlist)
residual_degs.push_back(lst.size());
vector<int> ll_next(g.n * 2);
vector<int> ll_prev(g.n * 2);
int *list_head = &ll_next[g.n];
int *list_tail = &ll_prev[g.n];
for (unsigned i=0; i<g.n; i++) {
list_head[i] = g.n + i;
list_tail[i] = g.n + i;
}
for (unsigned i=0; i<g.n; i++) {
int deg = residual_degs[i];
ll_prev[i] = g.n + deg;
ll_next[i] = list_head[deg];
ll_prev[ll_next[i]] = i;
list_head[deg] = i;
}
// printf("Made lists\n");
unsigned list_idx = g.n - 1;
vector<unsigned char> in_vv(g.n, 0);
for (;;) {
while (list_head[list_idx] >= int(g.n))
--list_idx;
if (list_idx == 0) {
for (unsigned v=0; v<g.n; v++) {
if (!in_vv[v]) {
vv.push_back(v);
}
}
std::reverse(vv.begin(), vv.end());
return vv;
}
int v = list_head[list_idx];
vv.push_back(v);
in_vv[v] = 1;
// remove from list
ll_next[ll_prev[v]] = ll_next[v];
ll_prev[ll_next[v]] = ll_prev[v];
for (int neighbour : g.adjlist[v]) {
if (!in_vv[neighbour]) {
// remove from list
ll_next[ll_prev[neighbour]] = ll_next[neighbour];
ll_prev[ll_next[neighbour]] = ll_prev[neighbour];
--residual_degs[neighbour];
int r = residual_degs[neighbour];
// insert into list
ll_prev[neighbour] = g.n + r;
ll_next[neighbour] = list_head[r];
ll_prev[ll_next[neighbour]] = neighbour;
list_head[r] = neighbour;
}
}
if (list_idx < g.n - 1)
++list_idx;
}
}
vector<long> calc_weighted_degs(const SparseGraph & g) {
vector<long> weighted_degs(g.n);
for (int v=0; v<int(g.n); v++)
for (auto w : g.adjlist[v])
weighted_degs[w] += g.weight[v];
return weighted_degs;
}
auto remove_vertices_with_closed_nd_wt_leq_incumbent(const SparseGraph & g,
vector<int> & vv, long current_wt, long incumbent_wt, int num_threads) -> void
{
vector<long> weighted_degs = calc_weighted_degs(g);
vv.erase(std::remove_if(vv.begin(), vv.end(),
[&g, &weighted_degs, current_wt, incumbent_wt](int v) {
return g.weight[v] + weighted_degs[v] + current_wt <= incumbent_wt;
}), vv.end());
}
auto reduce_and_reverse_cp_order(vector<int> & vv, const SparseGraph & g,
long current_wt, long incumbent_wt) -> void
{
if (vv.empty())
return;
auto residual_weighted_degs = calc_weighted_degs(g);
unsigned new_sz = vv.size();
for (unsigned i=vv.size(); i--; ) {
// find vertex with lowest residual_weighted_deg
unsigned best_v_pos = i;
long best_wt_deg = residual_weighted_degs[vv[i]];
for (unsigned j=i; j--; ) {
int v = vv[j];
if (residual_weighted_degs[v] < best_wt_deg) {
best_wt_deg = residual_weighted_degs[v];
best_v_pos = j;
}
}
int v = vv[best_v_pos];
std::swap(vv[best_v_pos], vv[i]);
if (new_sz==i+1 && g.weight[v] + best_wt_deg + current_wt <= incumbent_wt)
--new_sz;
for (int neighbour : g.adjlist[v])
residual_weighted_degs[neighbour] -= g.weight[v];
}
vv.resize(new_sz);
}