[geos-devel] Why many calls to signOfDet2x2 and addIntersections

[Norman Vine]

Martin Davis writes:
>
> Ok, after refreshing my brain about the JTS algorithms I can now shed some light on the mystery of why there are so many calls to
RobustDeterminant::signOfDet2x2 and SegmentIntersector SegmentIntersector::addIntersections.

Martin

It seems from your instrumentation that the JAVA code
is making ~10 times npoints calls but it is hard to tell exactly
Could you please add some instrumentation inside of signOfDet2x2()
and post the results of the TOTAL calls per test.


> Probably the real message here is that JTS has lived quite happily doing this all the time.  If GEOS is slower than JTS we have to
look elsewhere for the cause.

FWIW- My current TestLineSweep is running about
~20% faster then the Java results you posted

this is computed by elapsed_time * 733 / 1100

where my 733/1100 represents the speed of
my machine vs your machine

Of course this doesn't take into account lots of things
like different processors or memry speed

Norman