void SparseMatrix::sortRowsByIncreasingPivots() {
SparseMatrix ordered;
const auto rowCount = this->rowCount();
std::vector<RowIndex> rows(rowCount);
for (RowIndex row = 0; row < rowCount; ++row)
rows[row] = row;
const auto lexLess = [&](const RowIndex a, const RowIndex b) -> bool {
auto aIt = rowBegin(a);
auto bIt = rowBegin(b);
const auto aEnd = rowEnd(a);
const auto bEnd = rowEnd(b);
for (; aIt != aEnd && bIt != bEnd; ++aIt, ++bIt) {
if (*aIt < *bIt)
return true;
if (*aIt > *bIt)
return false;
++aIt;
++bIt;
}
return aIt == aEnd && bIt != bEnd;
};
std::sort(rows.begin(), rows.end(), lexLess);
// construct ordered with pivot columns in increasing order
ordered.clear();
for (size_t i = 0; i < rowCount; ++i)
ordered.appendRow(*this, rows[i]);
*this = std::move(ordered);
}
