Indeed, special-casing this when possible (string, not padded, etc.) to
avoid asprintf + strdup + two free() each helps enormously.
** Changed in: mksh
Status: Confirmed => Fix Committed
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https://bugs.launchpad.net/bugs/1855167
Title:
Comparatively poor += performance
Status in mksh:
Fix Committed
Bug description:
Heavy use of += notably impacts script performance. Consider the
following micro-benchmark (pattered after real script content):
i=0 s=
while ((i < 30000)); do
((++i))
s+=$i
done
which creates 138,894 character long string. On my system (macOS
10.14.6, 3.5 GHz i7), this takes ~8 seconds in mksh, compared with
ksh's ~0.1s and bash 5's ~0.3s. Here're `real' timing figures from
my most recent run (these figures are quite stable):
- mksh r57: 0m8.17s
- ksh 93u+ 2012-08-01: 0m0.10s
- bash 5.0.11(1)-release: 0m0.30s
It's no surprise that ksh93 is much faster, given its heavy
optimisation. Striking, though, is the poor performance of mksh
relative to the latest bash.
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