Re: Inlining comparators as a performance optimisation

On Tue, Sep 20, 2011 at 7:53 PM, Peter Geoghegan  wrote:
> I don't think that the fact that that happens is at all significant at
> this early stage, and it never even occurred to me that you'd think
> that it might be. I was simply disclosing a quirk of this POC patch.
> The workaround is probably to use a macro instead. For the benefit of
> those that didn't follow the other threads, the macro-based qsort
> implementation, which I found to perform significantly better than
> regular qsort(), runs like this on my laptop when I built at 02 with
> GCC 4.6 just now:
>
> C stdlib quick-sort time elapsed: 2.092451 seconds
> Inline quick-sort time elapsed: 1.587651 seconds

Results on my machine, for what they're worth:

[rhaas inline_compar_test]$ gcc -O0 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 2.366762 seconds
Inline quick-sort time elapsed: 1.807951 seconds
[rhaas inline_compar_test]$ gcc -O1 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.970473 seconds
Inline quick-sort time elapsed: 1.002765 seconds
[rhaas inline_compar_test]$ gcc -O2 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.966408 seconds
Inline quick-sort time elapsed: 0.958999 seconds
[rhaas inline_compar_test]$ gcc -O3 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.988693 seconds
Inline quick-sort time elapsed: 0.975090 seconds

-- 
Robert Haas
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