Substitution unexpectedly very slow, in Strawberry

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Substitution unexpectedly very slow, in Strawberry by choroba (Cardinal) on Aug 06, 2023 at 20:50 UTC
Just a comparison. `$^O eq 'linux'`: `0.254748821258545 0.255423069000244 v5.26.1 0.514794111251831 0.481626033782959 v5.37.3` [download] `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re: Substitution unexpectedly very slow, in Strawberry -- issue submitted by Discipulus (Canon) on Aug 10, 2023 at 08:43 UTC
Hello all, while I dont catch details involved, I care about perl to be lovely maintained and I know where to ask.. :) After knocking various `#irc` channels in `#p5p` I found the kind attention of `xenu` who digged this a bit deeply and opened Perl/perl5/issues/21360. A big ++ to `xenu` and to you all! L* There are no rules, there are no thumbs.. Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.	[reply] [d/l] [select]
Re: Substitution unexpectedly very slow, in Strawberry by swl (Prior) on Aug 06, 2023 at 22:21 UTC
Still occurs with Strawberry Perl 5.36.1 and 5.38.0 (see below) although I suspect it is more generic than Strawberry Perl. Running the code through nytprof shows 1000001 calls to main::CORE:substcont at line 10 take most of the time. It does not happen when the `$x` repetition is set to 1e5. There was a possibly related thread here a few months ago about character repetitions and COW but I can't locate it right now. `0.224835157394409 0.228233814239502 v5.22.3 9.92650699615479 0.662662982940674 v5.28.0 8.49285101890564 0.744230985641479 v5.36.1 8.02936911582947 0.788676977157593 v5.38.0` [download]	[reply] [d/l] [select]
Re^2: Substitution unexpectedly very slow, in Strawberry by syphilis (Archbishop) on Aug 07, 2023 at 02:13 UTC
There was a possibly related thread here a few months ago about character repetitions and COW but I can't locate it right now. It would be interesting to compare with a perl that was built without the COW. How might that be achieved on Windows ? (In fact, how is it even done on Linux ? IIRC it's fairly easily do-able on *nix but I can't find the relevant documentation.) On Windows, I'm seeing the same thing, irrespective of whether perl-5.38.0 is built with a mingw-w64 port of gcc or with Microsoft's Visual Studio 2022. Unthreaded builds of perl fare just as poorly as the multi-thread builds. The one thing that does make a big difference is to use a 32-bit build of perl. For example, with a 64-bit MSVC-built perl-5.38.0: `>perl time.pl 6.13913488388062 0.530965089797974 v5.38.0` [download] For a 32-bit perl-5.38.0 built using the same MSVC compiler (VS2022) in 32-bit mode: `>perl time.pl 0.0664510726928711 0.0533270835876465 v5.38.0` [download] But even with that 32-bit build of perl, the same issue becomes evident when "1e6" is changed to "2e6": `>perl time.pl 6.67774796485901 1.07769107818604 v5.38.0` [download] Cheers, Rob	[reply] [d/l] [select]
Re^3: Substitution unexpectedly very slow, in Strawberry by swl (Prior) on Aug 07, 2023 at 02:43 UTC
It also might not be related to COW and instead be something in the regex engine that is specific to windows. It's probably worth flagging with p5p.	[reply]
Re^4: Substitution unexpectedly very slow, in Strawberry by syphilis (Archbishop) on Aug 07, 2023 at 05:16 UTC
Re^5: Substitution unexpectedly very slow, in Strawberry by swl (Prior) on Aug 07, 2023 at 08:20 UTC
Some notes below your chosen depth have not been shown here
Re: Substitution unexpectedly very slow, in Strawberry by Discipulus (Canon) on Aug 07, 2023 at 07:26 UTC
More strawberry tastes :) \| 1.23387217521667 \| 0.566806077957153 \| v5.12.3 [OK] \perl5.12-32bit\perl\bin\perl.exe \| 0.269863128662109 \| 0.27295708656311 \| v5.20.3 [OK] \perl5.20.64bit\perl\bin\perl.exe \| 0.262228012084961 \| 0.269136905670166 \| v5.22.3 [OK] \perl5.22.64bit\perl\bin\perl.exe \| 0.294710159301758 \| 0.301361799240112 \| v5.24.2 [OK] \perl5.24.64bit\perl\bin\perl.exe \| 0.276448965072632 \| 0.271692037582397 \| v5.26.0 [OK] \perl5.26.64bit\perl\bin\perl.exe \| 0.282638788223267 \| 0.280515909194946 \| v5.26.2 [OK] \perl-5.26.64bit-PDL\perl\bin\perl.exe \| 3.31176686286926 \| 0.708863019943237 \| v5.28.0 [OK] \perl5.28.32bit\perl\bin\perl.exe \| 11.2146329879761 \| 0.633802890777588 \| v5.28.1 [OK] \perl5.28-64bit\perl\bin\perl.exe \| 11.6474039554596 \| 0.678498983383179 \| v5.32.0 [OK] \perl5.32.64bit\perl\bin\perl.exe [download] L* There are no rules, there are no thumbs.. Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.	[reply] [d/l]