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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.org). *
* *
* 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 2 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* 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 <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include <algorithm>
#include "split/sigisomorphism.h"
namespace regina {
SigPartialIsomorphism::SigPartialIsomorphism(
const SigPartialIsomorphism& iso) : nLabels(iso.nLabels),
nCycles(iso.nCycles),
labelImage(iso.nLabels ? new unsigned[iso.nLabels] : nullptr),
cyclePreImage(iso.nCycles ? new unsigned[iso.nCycles] : nullptr),
cycleStart(iso.nCycles ? new unsigned[iso.nCycles] : nullptr),
dir(iso.dir) {
if (iso.nLabels)
std::copy(iso.labelImage, iso.labelImage + iso.nLabels, labelImage);
if (iso.nCycles) {
std::copy(iso.cyclePreImage, iso.cyclePreImage + iso.nCycles,
cyclePreImage);
std::copy(iso.cycleStart, iso.cycleStart + iso.nCycles, cycleStart);
}
}
SigPartialIsomorphism::SigPartialIsomorphism(
const SigPartialIsomorphism& base,
unsigned newLabels, unsigned newCycles) : nLabels(newLabels),
nCycles(newCycles),
labelImage(newLabels ? new unsigned[newLabels] : nullptr),
cyclePreImage(newCycles ? new unsigned[newCycles] : nullptr),
cycleStart(newCycles ? new unsigned[newCycles] : nullptr),
dir(base.dir) {
if (base.nLabels)
std::copy(base.labelImage, base.labelImage + base.nLabels, labelImage);
if (base.nCycles) {
std::copy(base.cyclePreImage, base.cyclePreImage + base.nCycles,
cyclePreImage);
std::copy(base.cycleStart, base.cycleStart + base.nCycles, cycleStart);
}
}
SigPartialIsomorphism& SigPartialIsomorphism::operator = (
const SigPartialIsomorphism& src) {
// std::copy() exhibits undefined behaviour in the case of self-assignment.
if (std::addressof(src) == this)
return *this;
if (nLabels != src.nLabels) {
delete[] labelImage;
nLabels = src.nLabels;
labelImage = new unsigned[nLabels];
}
if (nCycles != src.nCycles) {
delete[] cyclePreImage;
delete[] cycleStart;
nCycles = src.nCycles;
cyclePreImage = new unsigned[nCycles];
cycleStart = new unsigned[nCycles];
}
std::copy(src.labelImage, src.labelImage + nLabels, labelImage);
std::copy(src.cyclePreImage, src.cyclePreImage + nCycles, cyclePreImage);
std::copy(src.cycleStart, src.cycleStart + nCycles, src.cycleStart);
dir = src.dir;
return *this;
}
bool SigPartialIsomorphism::operator == (const SigPartialIsomorphism& other)
const {
return
nLabels == other.nLabels &&
nCycles == other.nCycles &&
dir == other.dir &&
std::equal(labelImage, labelImage + nLabels, other.labelImage) &&
std::equal(cyclePreImage, cyclePreImage + nCycles,
other.cyclePreImage) &&
std::equal(cycleStart, cycleStart + nCycles, other.cycleStart);
}
void SigPartialIsomorphism::makeCanonical(const Signature& sig,
unsigned fromCycleGroup) {
unsigned fromCycle, toCycle;
unsigned c, i;
unsigned cycleLen;
unsigned start1, start2;
// Deal with each cycle group separately.
for ( ; sig.cycleGroupStart[fromCycleGroup] < nCycles; fromCycleGroup++) {
fromCycle = sig.cycleGroupStart[fromCycleGroup];
toCycle = sig.cycleGroupStart[fromCycleGroup + 1];
if (toCycle > nCycles)
toCycle = nCycles;
if (fromCycle >= toCycle)
continue;
// Determine where each cycle should start.
cycleLen = sig.cycleStart[fromCycle + 1] - sig.cycleStart[fromCycle];
for (c = fromCycle; c < toCycle; c++) {
start1 = start2 = cycleLen;
for (i = 0; i < cycleLen; i++)
if (start1 == cycleLen ||
labelImage[sig.label[sig.cycleStart[c] + i]] <
labelImage[sig.label[sig.cycleStart[c] + start1]]) {
start1 = i;
start2 = cycleLen;
} else if (labelImage[sig.label[sig.cycleStart[c] + i]] ==
labelImage[sig.label[sig.cycleStart[c] + start1]])
start2 = i;
if (start2 == cycleLen)
cycleStart[c] = start1;
else {
// Two possible starting points; we must choose between them.
if (sig.cycleCmp(
c, start1, dir, labelImage,
c, start2, dir, labelImage) <= 0)
cycleStart[c] = start1;
else
cycleStart[c] = start2;
}
}
// At this point we now know where each cycle starts under the new
// labelling. It's now time to determine in which order the cycles
// should be presented.
for (c = fromCycle; c < toCycle; c++)
cyclePreImage[c] = c;
std::sort(cyclePreImage + fromCycle, cyclePreImage + toCycle,
ShorterCycle(sig, *this));
}
}
int SigPartialIsomorphism::compareWith(const Signature& sig,
const SigPartialIsomorphism& other, unsigned fromCycleGroup) const {
for (unsigned c = sig.cycleGroupStart[fromCycleGroup]; c < nCycles; c++) {
int result = sig.cycleCmp(
cyclePreImage[c], cycleStart[cyclePreImage[c]], dir, labelImage,
other.cyclePreImage[c], other.cycleStart[other.cyclePreImage[c]],
other.dir, other.labelImage);
if (result < 0)
return -1;
if (result > 0)
return 1;
}
return 0;
}
int SigPartialIsomorphism::compareWithIdentity(const Signature& sig,
unsigned fromCycleGroup) const {
for (unsigned c = sig.cycleGroupStart[fromCycleGroup]; c < nCycles; c++) {
int result = sig.cycleCmp(
cyclePreImage[c], cycleStart[cyclePreImage[c]], dir, labelImage,
c, 0, 1, nullptr);
if (result < 0)
return -1;
if (result > 0)
return 1;
}
return 0;
}
void SigPartialIsomorphism::writeTextShort(std::ostream& out) const {
if (nLabels == 0)
out << "No symbols mapped";
else {
out << "Symbols: ";
for (unsigned i = 0; i < nLabels; ++i)
out << char('a' + i);
out << " -> ";
for (unsigned i = 0; i < nLabels; ++i)
out << char('a' + labelImage[i]);
}
out << "; ";
if (nCycles == 0)
out << "no cycles mapped";
else {
out << "cycles: ";
for (unsigned i = 0; i < nCycles; ++i) {
if (i > 0)
out << ", ";
out << cyclePreImage[i] << " -> " << i;
if (cycleStart[cyclePreImage[i]] > 0)
out << " (>> " << cycleStart[cyclePreImage[i]] << ')';
}
}
if (dir < 0)
out << ", all reversed";
}
} // namespace regina
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