[Xapian-discuss] 1.2.2/3 performance issue

[Olly Betts]

On Tue, Aug 31, 2010 at 03:40:17PM +0200, Markus Wörle wrote:
> Am 31.08.2010 um 15:04 schrieb Olly Betts:
> > On Tue, Aug 31, 2010 at 02:25:52PM +0200, Markus Wörle wrote:
> >> Do have any idea yet what change from 1.2.0 to 1.2.2 could have been caused
> >> the slowdown?
> > 
> > If this is on x86 (not x86-64), then try running configure with
> > --disable-sse.
> > 
> > 1.2.1 defaults to use SSE for floating point on x86 (rather than 387
> > instructions) which avoids issues with excess precision.  In my tests
> > SSE was actually faster, but I suppose that may vary between CPU models.
> 
> It's a x86-64 linux on a Xeon (X5450) based system. I tried it anyway, but
> --disable-sse did not change anything.

Indeed - it only does anything on x86.

Nothing else looks likely.  There are a couples of correctness fixes (tickets
#475 and #476) but I'd be surprised if they had such a drastic effect.

You could try 1.2.1, but there were a lot of changes between 1.2.0 and 1.2.1
and not many between 1.2.1 and 1.2.2, so it's likely 1.2.1 is affected too.

Beyond hat you could try a binary chop on SVN to find where this started if
you have a simple case to check each time.

Or coming at it from the other end, the output of Query::get_description()
for some of the slow queries might help to narrow it down.

Cheers,
    Olly