https://issues.dlang.org/show_bug.cgi?id=17161
--- Comment #2 from Jack Stouffer <j...@jackstouffer.com> --- Bad news: I see a similar performance decrease for run-time regex as well. # 2.073.0 $ dmd -O -inline -release test2.d && cat input5000000.txt | time ./test2 ./test2 4.44s user 0.09s system 98% cpu 4.591 total # 2.072.2 ~/digger/result/bin/dmd -O -inline -release test2.d && cat input5000000.txt | time ./test2 ./test2 3.20s user 0.09s system 98% cpu 3.344 total I consistently get around a second and a half longer run time with 2.073. Code import std.algorithm; import std.array; import std.range; import std.regex; import std.stdio; import std.typecons; import std.utf; static variants = [ "agggtaaa|tttaccct", "[cgt]gggtaaa|tttaccc[acg]", "a[act]ggtaaa|tttacc[agt]t", "ag[act]gtaaa|tttac[agt]ct", "agg[act]taaa|ttta[agt]cct", "aggg[acg]aaa|ttt[cgt]ccct", "agggt[cgt]aa|tt[acg]accct", "agggta[cgt]a|t[acg]taccct", "agggtaa[cgt]|[acg]ttaccct", ]; void main() { auto app = appender!string; app.reserve(5_000_000); app.put(stdin .byLineCopy(KeepTerminator.yes) .joiner .byChar); auto seq = app.data; auto regexLineFeeds = regex(">.*\n|\n"); seq = seq.replaceAll(regexLineFeeds, ""); foreach (pattern; variants) { writeln(pattern, " ", seq.matchAll(pattern).walkLength); } } --