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kpkc.cpp
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kpkc.cpp
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#include "kpkc.h"
#if __POPCNT__ || __BMI__
#include <immintrin.h>
#endif
#include <csignal>
#include <iostream>
#include <stdlib.h>
using namespace std;
// Handle keyboard
// interrupts
namespace {
volatile sig_atomic_t kpkc_interrupted = 0;
void interrupt_signal_handler(int signal) {
kpkc_interrupted = 1;
}
struct sigaction prev_action;
struct sigaction prev_action2;
struct sigaction sigIntHandler;
#define RESTORE_SIGNALS sigaction(SIGINT, &prev_action, NULL); \
sigaction(SIGALRM, &prev_action2, NULL);
#define REGISTER_SIGNALS \
sigIntHandler.sa_handler = interrupt_signal_handler; \
sigemptyset(&sigIntHandler.sa_mask); \
sigIntHandler.sa_flags = 0; \
sigaction(SIGINT, &sigIntHandler, &prev_action); \
sigaction(SIGALRM, &sigIntHandler, &prev_action2);
#define CHECK_FOR_INTERRUPT \
if (kpkc_interrupted) { \
kpkc_interrupted = 0; \
RESTORE_SIGNALS \
throw runtime_error("computation with kpkc was interrupted"); \
}
// Bitset helpers.
int popcount(uint64_t i){
#if (__POPCNT__) && (INTPTR_MAX == INT64_MAX)
return _mm_popcnt_u64(i);
#else
i = i - ((i >> 1) & 0x5555555555555555ULL);
i = (i & 0x3333333333333333ULL) + ((i >> 2) & 0x3333333333333333ULL);
return ( ((i + (i >> 4)) & 0x0f0f0f0f0f0f0f0fULL) * 0x0101010101010101ULL ) >> 56;
#endif
}
uint64_t lower_n_bits(int n){
return ((uint64_t) -1) >> (64 - n);
}
int first_in_limb(uint64_t i){
// Return the position of the first bit.
//
// Assumes that ``i`` is nonzero.
#if (__BMI__) && (INTPTR_MAX == INT64_MAX)
return _tzcnt_u64(i);
#else
int output = 63;
(i & 0x00000000FFFFFFFF) ? output -= 32 : (i >>= 32);
(i & 0x000000000000FFFF) ? output -= 16 : (i >>= 16);
(i & 0x00000000000000FF) ? output -= 8 : (i >>= 8);
(i & 0x000000000000000F) ? output -= 4 : (i >>= 4);
(i & 0x0000000000000003) ? output -= 2 : (i >>= 2);
if (i & 0x0000000000000001) output -= 1;
return output;
#endif
}
}
namespace kpkc
{
// Bitsets
Bitset::Bitset(int n_vertices, bool fill){
/*
Initalize bitset.
Fill if ``fill``.
*/
allocate(n_vertices);
if (!fill)
return;
// Fill.
for(int i=0; i<n_vertices/64; i++){
data[i] = -1;
}
// Remove trailing bits.
if (n_vertices % 64)
data[n_vertices/64] = lower_n_bits(n_vertices % 64);
}
Bitset::Bitset(const bool* set_bits, int n_vertices){
/*
Initialize bitset with the given bits.
*/
allocate(n_vertices);
for(int i=0; i < (n_vertices-1)/64 + 1; i++)
data[i] = 0;
for(int i=0; i<n_vertices; i++){
if (set_bits[i])
set(i);
}
}
void Bitset::intersection_assign(const Bitset& l, const Bitset& r){
// Assumes all of same length.
for (int i=0; i<limbs; i++)
data[i] = l[i] & r[i];
}
int Bitset::intersection_count(const Bitset& r, int start, int stop) const {
/*
Count the number of set bits in ``this & r``
in ``range(start, stop)``.
*/
int counter = 0;
// The easy part, count any complete ``uint64_t``.
for (int i=start/64 + 1; i< stop/64; i++)
counter += popcount(data[i] & r[i]);
uint64_t start_limb = data[start/64] & r[start/64];
if (start % 64)
// Remove the lower bits.
start_limb &= ~lower_n_bits(start % 64);
if (stop % 64 == 0)
return counter + popcount(start_limb);
uint64_t end_limb = 0;
if (stop/64 < limbs){
end_limb = data[stop/64] & r[stop/64];
// Remove the upper bits.
end_limb &= lower_n_bits(stop % 64);
}
if (start/64 == stop/64){
// The start limb is the end limb.
counter += popcount(start_limb & end_limb);
} else {
if (stop/64 < limbs){
counter += popcount(start_limb) + popcount(end_limb);
} else {
// There is no end limb.
counter += popcount(start_limb);
}
}
return counter;
}
int Bitset::count(int start, int stop) const {
/*
Count the number of set bits in ``this``
in ``range(start, stop)``.
*/
int counter = 0;
// The easy part, count any complete ``uint64_t``.
for (int i=start/64 + 1; i< stop/64; i++)
counter += popcount(data[i]);
uint64_t start_limb = data[start/64];
if (start % 64)
// Remove the lower bits.
start_limb &= ~lower_n_bits(start % 64);
if (stop % 64 == 0)
return counter + popcount(start_limb);
uint64_t end_limb = 0;
if (stop/64 < limbs){
end_limb = data[stop/64];
// Remove the upper bits.
end_limb &= lower_n_bits(stop % 64);
}
if (start/64 == stop/64){
// The start limb is the end limb.
counter += popcount(start_limb & end_limb);
} else {
if (stop/64 < limbs){
counter += popcount(start_limb) + popcount(end_limb);
} else {
// There is no end limb.
counter += popcount(start_limb);
}
}
return counter;
}
int Bitset::first(int start) const {
/*
Return the first bit in ``this``
in ``range(start, stop)``.
It assumes that the range is valid and that there is at least on non-zero bit.
*/
uint64_t start_limb = data[start/64];
if (start % 64)
// Remove the lower bits.
start_limb &= ~lower_n_bits(start % 64);
int counter = (start/64)*64;
if (start_limb)
return counter + first_in_limb(start_limb);
else
counter += 64;
// The easy part, count any complete ``uint64_t``.
for (int i=start/64 + 1; i< limbs; i++){
if (data[i])
return counter + first_in_limb(data[i]);
else
counter += 64;
}
return limbs * 64;
}
void Bitset::set(int index){
data[index/64] |= one_set_bit(index % 64);
}
void Bitset::allocate(int n_vertices){
limbs = ((n_vertices-1)/64+ 1);
data.resize(limbs);
}
// KPartiteKClique
template<Algorithm A>
KPartiteKClique<A>::KPartiteKClique(const bool* const* incidences, const int n_vertices, const int* first_per_part, const int k, const int prec_depth){
if (k <= 0) throw invalid_argument("k must be at least 1");
current_depth = 0;
_k_clique = vector<int>(k);
parts = vector<int>(k+1);
for (int i=0; i<k; i++){
parts[i] = first_per_part[i];
}
parts[k] = n_vertices;
for (int i=0; i<k; i++){
if (parts[i+1] - parts[i] == 0)
throw invalid_argument("parts may not be empty");
}
this->n_vertices = n_vertices;
this->k = k;
// use clear to preserve capacity
all_vertices.clear();
int current_part = 0;
for (int i=0; i<n_vertices; i++){
while ((current_part < k-1) && (i >= parts[current_part + 1]))
current_part += 1;
all_vertices.push_back(Vertex_template(this, incidences[i], n_vertices, current_part, i));
}
this->prec_depth = prec_depth;
recursive_graphs = vector<KPartiteGraph>();
for (int i=0; i<k; i++){
recursive_graphs.push_back(KPartiteGraph(this, i==0));
}
finish_init();
}
template<>
void KPartiteKClique<kpkc>::finish_init(){
// Assign vertices to the first graph.
recursive_graphs.front().vertices.assign(all_vertices.begin(), all_vertices.end());
// Set weights twice, if there is new knowledge already.
if (recursive_graphs.front().set_weights())
recursive_graphs.front().set_weights();
sort(recursive_graphs.front().vertices.begin(), recursive_graphs.front().vertices.end());
}
template<>
void KPartiteKClique<FindClique>::finish_init(){
// Take care of trivial parts.
// ``set_part_sizes`` assumes that parts of size 1 were selected
// already, which would not be the case, if the part is 1 to start
// with.
for (int i=0; i<k; i++){
if (parts[i+1] - parts[i] == 1)
current_graph()->part_sizes[i] = 2;
}
recursive_graphs.front().set_part_sizes();
}
template<Algorithm A>
bool KPartiteKClique<A>::next(){
/*
Set the next clique.
Return whether there is a next clique.
*/
REGISTER_SIGNALS
while (true){
if (current_depth < k-1){
// Note that the interrupt can also be abused to pause.
CHECK_FOR_INTERRUPT
if (!current_graph()->select(next_graph())){
if (!backtrack()){
// Out of options.
RESTORE_SIGNALS
return false;
}
}
} else {
if (!current_graph()->select()){
if (!backtrack()){
// Out of options.
RESTORE_SIGNALS
return false;
}
} else {
RESTORE_SIGNALS
return true;
}
}
}
}
// Vertex_template
template<Algorithm A>
KPartiteKClique<A>::Vertex_template::Vertex_template(KPartiteKClique<A>* problem, const bool* incidences, int n_vertices, int part, int index){
bitset = Bitset(incidences, n_vertices);
this->part = part;
this->index = index;
this->problem = problem;
// Set each vertex adjacent to itself.
// This is important, so that after selecting a vertex
// the corresponding part will have one ``active_vertex``.
bitset.set(index);
}
// KPartiteGraph
template<Algorithm A>
KPartiteKClique<A>::KPartiteGraph::KPartiteGraph(KPartiteKClique<A>* problem, bool fill){
vertices = vector<Vertex>();
active_vertices = Bitset(problem->n_vertices, fill);
part_sizes = vector<int>(problem->k+1);
for (int i=0; i < problem->k; i++){
part_sizes[i] = problem->parts[i+1] - problem->parts[i];
}
this->problem = problem;
}
template<>
bool KPartiteKClique<FindClique>::KPartiteGraph::select(KPartiteGraph* next){
/*
Select the first vertex in the smallest part.
Return false, if there are no vertices left.
*/
assert(selected_part != -1); // Should not be called, if we found a clique already.
if (!part_sizes[selected_part])
return false;
// Copy the current sizes.
for (int i=0; i<get_k(); i++)
next->part_sizes[i] = part_sizes[i];
next->part_sizes[selected_part] = 1;
// Select v.
int v = first(selected_part);
if (v == -1) return false;
problem->_k_clique[selected_part] = v;
intersection(next->active_vertices, problem->all_vertices[v], active_vertices);
// v may no longer be selected on the next call.
pop_vertex(selected_part, v);
// Raise the current
// depth, such that the
// parts get set
// accordingly.
problem->current_depth += 1;
return next->set_part_sizes();
}
template<>
bool KPartiteKClique<FindClique>::KPartiteGraph::select(){
/*
Select the first vertex in the smallest part.
Return false, if there are no vertices left.
It is assumed that there is no next graph.
*/
assert(selected_part != -1); // Should not be called, if we found a clique already.
assert(problem->current_depth == problem->k -1);
if (!part_sizes[selected_part])
return false;
// Select v.
int v = first(selected_part);
if (v == -1) return false;
problem->_k_clique[selected_part] = v;
// v may no longer be selected on the next call.
pop_vertex(selected_part, v);
return true;
}
}