From: Martin Kronbichler Date: Fri, 13 Oct 2023 18:05:05 +0000 (+0200) Subject: AffineConstraints::close(): Avoid sorting of sorted list X-Git-Tag: relicensing~394^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=76b5ea698495bfc8b70955c00308fc9f15dab6cc;p=dealii.git AffineConstraints::close(): Avoid sorting of sorted list --- diff --git a/include/deal.II/lac/affine_constraints.templates.h b/include/deal.II/lac/affine_constraints.templates.h index eb2029bd43..3b4c4cf3a6 100644 --- a/include/deal.II/lac/affine_constraints.templates.h +++ b/include/deal.II/lac/affine_constraints.templates.h @@ -954,25 +954,33 @@ AffineConstraints::close() for (ConstraintLine &line : boost::iterator_range< typename std::vector::iterator>(begin, end)) { - std::sort(line.entries.begin(), - line.entries.end(), - [](const std::pair &a, - const std::pair &b) -> bool { - // Let's use lexicographic ordering with std::abs for - // number type (it might be complex valued). - return (a.first < b.first) || - (a.first == b.first && - std::abs(a.second) < std::abs(b.second)); - }); - - // loop over the now sorted list and see whether any of the entries - // references the same dofs more than once in order to find how many - // non-duplicate entries we have. This lets us allocate the correct - // amount of memory for the constraint entries. - size_type duplicates = 0; - for (size_type i = 1; i < line.entries.size(); ++i) - if (line.entries[i].first == line.entries[i - 1].first) - ++duplicates; + unsigned int duplicates = 0; + bool is_sorted_without_duplicates = true; + for (unsigned int i = 1; i < line.entries.size(); ++i) + if (!(line.entries[i - 1].first < line.entries[i].first)) + { + is_sorted_without_duplicates = false; + break; + } + if (is_sorted_without_duplicates == false) + { + std::sort(line.entries.begin(), + line.entries.end(), + [](const std::pair &a, + const std::pair &b) -> bool { + // Just look at the index, ignore the value. + return a.first < b.first; + }); + + // loop over the now sorted list and see whether any of the + // entries references the same dofs more than once in order to + // find how many non-duplicate entries we have. This lets us + // allocate the correct amount of memory for the constraint + // entries. + for (size_type i = 1; i < line.entries.size(); ++i) + if (line.entries[i].first == line.entries[i - 1].first) + ++duplicates; + } if (duplicates > 0 || (line.entries.size() < line.entries.capacity())) {