[Issue 17820] std.regex performance: .matchFirst allocates frequently; causes thread contention

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17820

--- Comment #1 from Chad Joan <chadjoan at gmail.com> ---
The benchmark output seems like it might wrap poorly in bugzilla's page, so
here is an edited version that should fit better:

Windows 7 machine with dmd v2.076.0:
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C:\dprojects\regex\benchmark>dmd main.d -release -O -m64

C:\dprojects\regex\benchmark>main
non-regex parsing, parallel:            100000 elements in 0.061s.
regex parsing, no captures, parallel:   100000 elements in 202.893 s.
regex parsing, many captures, parallel: 100000 elements in 977.339 s.
non-regex parsing, serial:              100000 elements in 0.031 s.
regex parsing, no captures, serial:     100000 elements in 202.395 s.
regex parsing, many captures, serial:   100000 elements in 837.401 s.
--------------------------------------------------------

Slightly slower (hardware-wise) Linux (Gentoo) machine with dmd v2.074.1:
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$ dmd main.d -release -O -m64
$ ./main
non-regex parsing, parallel:            100000 elements in 0.062 s.
regex parsing, no captures, parallel:   100000 elements in 88.055 s.
regex parsing, many captures, parallel: 100000 elements in 93.546 s.
non-regex parsing, serial:              100000 elements in 0.043 s.
regex parsing, no captures, serial:     100000 elements in 135.063 s.
regex parsing, many captures, serial:   100000 elements in 135.250 s.
--------------------------------------------------------

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