Re: qsort again (was Re: Strange Create Index

[Neil Conway <neilc(at)samurai(dot)com>]

On Thu, 2006-02-16 at 12:35 +0100, Steinar H. Gunderson wrote:
> glibc-2.3.5/stdlib/qsort.c:
> 
>   /* Order size using quicksort.  This implementation incorporates
>      four optimizations discussed in Sedgewick:
> 
> I can't see any references to merge sort in there at all.

stdlib/qsort.c defines _quicksort(), not qsort(), which is defined by
msort.c. On looking closer, it seems glibc actually tries to determine
the physical memory in the machine -- if it is sorting a single array
that exceeds 1/4 of the machine's physical memory, it uses quick sort,
otherwise it uses merge sort.

-Neil