Re: Re: Which qsort is used

> -----Original Message-----
> From: Qingqing Zhou [mailto:zhouqq(at)cs(dot)toronto(dot)edu]
> Sent: Friday, December 16, 2005 10:13 PM
> To: Dann Corbit
> Cc: Tom Lane; Bruce Momjian; Luke Lonergan; Neil Conway; pgsql-
> hackers(at)postgresql(dot)org
> Subject: RE: [HACKERS] Re: Which qsort is used
>
>
>
> On Sat, 17 Dec 2005, Dann Corbit wrote:
>
> >
> > The benchmarks say that they (order checks) are a good idea on
average
> > for ordered data, random data, and partly ordered data.
> >
>
> I interpret that in linux, 5000000 seems a divide for qsortpdq. Before
> that number, it wins, after that, bsd wins more. On SunOS, qsortpdq
takes
> the lead till the last second -- I suspect this is due to the rand()
> function:
>
> Linux - #define RAND_MAX 2147483647
> SunOS - #define RAND_MAX 32767
>
> So in SunOS, the data actually not that scattered - so more favourate
for
> sorted() or reversed() check?

There is a lot of variability from system to system even for the same
tests. I see different results depending on whether I use GCC or Intel
or MS compilers.