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/*****************************************************************************
CryptoMiniSat -- Copyright (c) 2009 Mate Soos
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
******************************************************************************/
#include <iostream>
#include <vector>
#include "../Solver/SolverTypes.h"
#include "SCCFinder.h"
#include "VarReplacer.h"
#include <iomanip>
#include "time_mem.h"
#include "Subsumer.h"
#include "XorSubsumer.h"
using namespace CMSat;
SCCFinder::SCCFinder(Solver& _solver) :
solver(_solver)
, varElimed1(_solver.subsumer->getVarElimed())
, varElimed2(_solver.xorSubsumer->getVarElimed())
, replaceTable(_solver.varReplacer->getReplaceTable())
, totalTime(0.0)
{}
bool SCCFinder::find2LongXors()
{
double myTime = cpuTime();
uint32_t oldNumReplace = solver.varReplacer->getNewToReplaceVars();
globalIndex = 0;
index.clear();
index.resize(solver.nVars()*2, std::numeric_limits<uint32_t>::max());
lowlink.clear();
lowlink.resize(solver.nVars()*2, std::numeric_limits<uint32_t>::max());
stackIndicator.clear();
stackIndicator.growTo(solver.nVars()*2, false);
assert(stack.empty());
for (uint32_t vertex = 0; vertex < solver.nVars()*2; vertex++) {
//Start a DFS at each node we haven't visited yet
if (index[vertex] == std::numeric_limits<uint32_t>::max()) {
recurDepth = 0;
tarjan(vertex);
assert(stack.empty());
}
}
if (solver.conf.verbosity >= 3 || (solver.conflicts == 0 && solver.conf.verbosity >= 1)) {
std::cout << "c Finding binary XORs T: "
<< std::fixed << std::setprecision(2) << std::setw(8) << (cpuTime() - myTime) << " s"
<< " found: " << std::setw(7) << solver.varReplacer->getNewToReplaceVars() - oldNumReplace
<< std::endl;
}
totalTime += (cpuTime() - myTime);
return solver.ok;
}
void SCCFinder::tarjan(const uint32_t vertex)
{
recurDepth++;
index[vertex] = globalIndex; // Set the depth index for v
lowlink[vertex] = globalIndex;
globalIndex++;
stack.push(vertex); // Push v on the stack
stackIndicator[vertex] = true;
Var vertexVar = Lit::toLit(vertex).var();
if (!varElimed1[vertexVar] && !varElimed2[vertexVar]) {
const vec<Watched>& ws = solver.watches[vertex];
for (vec<Watched>::const_iterator it = ws.getData(), end = ws.getDataEnd(); it != end; it++) {
if (!it->isBinary()) continue;
const Lit lit = it->getOtherLit();
doit(lit, vertex);
}
if (solver.conf.doExtendedSCC) {
Lit vertLit = Lit::toLit(vertex);
vector<Lit>& transCache = solver.transOTFCache[(~Lit::toLit(vertex)).toInt()].lits;
vector<Lit>::iterator it = transCache.begin();
vector<Lit>::iterator it2 = it;
uint32_t newSize = 0;
Lit prevLit = lit_Error;
for (vector<Lit>::iterator end = transCache.end(); it != end; it++) {
Lit lit = *it;
lit = replaceTable[lit.var()] ^ lit.sign();
if (lit == prevLit || lit == vertLit || varElimed1[lit.var()] || varElimed2[lit.var()])
continue;
*it2++ = lit;
prevLit = lit;
newSize++;
doit(lit, vertex);
}
transCache.resize(newSize);
}
}
// Is v the root of an SCC?
if (lowlink[vertex] == index[vertex]) {
uint32_t vprime;
tmp.clear();
do {
assert(!stack.empty());
vprime = stack.top();
stack.pop();
stackIndicator[vprime] = false;
tmp.push(vprime);
} while (vprime != vertex);
if (tmp.size() >= 2) {
for (uint32_t i = 1; i < tmp.size(); i++) {
if (!solver.ok) break;
vec<Lit> lits(2);
lits[0] = Lit::toLit(tmp[0]).unsign();
lits[1] = Lit::toLit(tmp[i]).unsign();
const bool xorEqualsFalse = Lit::toLit(tmp[0]).sign()
^ Lit::toLit(tmp[i]).sign()
^ true;
if (solver.value(lits[0]) == l_Undef && solver.value(lits[1]) == l_Undef) {
//Cannot add to watchlists, because we are going THROUGH the watchlists (in a higher frame)
//so it might end up kicking the chair under ourselves
solver.varReplacer->replace(lits, xorEqualsFalse, true, false);
}
}
}
}
}
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