Re: Sorting a TOrdCollection...

Sverre JARP (Sverre.Jarp@cern.ch)
Tue, 03 Jun 1997 07:03:27 +0200

Fons Rademakers wrote:
>
> I finally had some time to investigate this problem.
> On my PPro 200 Linux box I was able to sort 1.000.000
> TObjStrings of the form:
> [snip]
> stored in a TOrdCollection or TObjArray in 85 seconds.
About 130 MB was used for this test and
> my machine has 256 MB.
>
> Anyway the 79 seconds for 1.000.000 strings is not
> too bad. So now the question is: what happened in
> your case where it took 400 CP seconds to sort 22.000
> strings.

Fons and Jim,
Here is my view on the problem:
The QSORT algorithm is fine if you have enough memory, but it seems to
drive the paging disks crazy if you don't.
This morning I tried Fons's example on a NT machine with 96 MB but I
gave up waiting for it to terminate !!
Then I reduced the size to 500.000 strings (the space requirement is
then 65-70 MB) and the unoptimised version of the example terminated in
39 seconds !
So with this algorithm the rule seems to be: Make sure you have enough
REAL memory to hold the whole TObjArray.
Sverre
_________________________________________________

Sverre Jarp Email: Sverre.Jarp@Cern.CH
IT Department Phone: +41.79.201.0134
CERN Phone at CERN: 16.0134
CH- 1211 Geneva 23 Fax: +41.22.767.7155
_________________________________________________