[issue28397] Faster index range checks
Stefan Krah
report at bugs.python.org
Tue Oct 11 09:30:58 EDT 2016
Stefan Krah added the comment:
On 64-bit Linux there's no difference:
$ ./usr/bin/gcc -O3 -o issue28397-2 issue28397-2.c
$ time ./issue28397-2 0
real 0m2.486s
user 0m2.424s
sys 0m0.014s
$ time ./issue28397-2 1
real 0m2.433s
user 0m2.422s
sys 0m0.008s
Also, most of the time "index < 0 || index >= nitems" *is* inlined,
and it was at least three times faster here.
I guess the general point is that such micro-optimizations are
unpredictable on modern architectures and modern compilers.
Note that the fast inlined version used SSE instructions.
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<http://bugs.python.org/issue28397>
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