Re: Comparaison between PARI MPQS, PPMPQS and PPSIGS

[Bill Allombert <allomber@math.u-bordeaux.fr>]

On Tue, Dec 03, 2002 at 04:34:56PM -0500, Igor Schein wrote:
> On Wed, Nov 27, 2002 at 05:26:39PM +0100, Bill Allombert wrote:
> > Hello developers,
> > 
> > I have factored 
> > 117433370311644622074182931512170893877890957626285922622753078073774028918529
> > (78 digits)
> > 
> > on a 1GHz PIV
> > with PARI (2.2.5), and then I try PPMPQS (2.8) and PPSIGS (1.1) from 
> > http://www.asahi-net.or.jp/~KC2H-MSM/cn/
> > 
> > here the running time:
> > PARI   : 3h 9 min
> > PPMPQS : 1h 58 min
> > PPSIGS : 1h 46 min
> > 
> > Karim's FAQ states 
> > 
> > > PARI's MPQS is about as fast as PPMPQS-2.7 in the 60 digits range, and much
> > > slower afterwards, e.g already 3 times slower for 70 digits. We have not
> > > tested mpqs4linux.
> 
> Well, here's a problem with PARI's MPQS on Linux which I noticed some
> time ago. If you run N consecutive factorizations with PPxxxx on the
> same number, the timing results will be consistent.  Not so the case
> for PARI.  Here's the timings for several consecutive MPQS
> factorizations of C78 above on an otherwise empty machine: 

For the record, my timings were done two time each and I got 
consistent results.

Maybe it is a difference in disk usages, maybe PPMPQS as its own internal
buffering. Also they do not store temporary files in the same directory.
This can make a difference.

Also you may want to delete the temporary files created between each run.

> The speed is constant within each session, it's just that some
> sessions are faster, some sessions are slower for no apparent reason.  
> 
> Based on above, it's really hard to compare speed for this size
> integer on Linux.  However, I was able to obtain more consistent
> results for C60=nextprime(10^60)*precprime(10^60) - PPSIGS is almost
> twice faster than PARI on a 512MB full speed L2 cache Linux machine. 

I suppose you mean nextprime(10^30)*precprime(10^30), else you must
have a Cray.

Cheers,
Bill.