[PPL-devel] Question regarding speed of the library

[Martin Rohde]

Hello,

I have a question regarding the speed of the PPL0.4.1 library.

I'm using the library now for calculating the intersection of two convex 
polyhedra. During my calculations, a large number of intersections must 
be calculated (say 50000 times). The library does its calculations very 
well, but it costs a lot of time to calculate an intersection. In my 
code I do the following:

1. Add generators to a polyhedron 1
2. Add generators to a polyhedron 2
3. Calculate the intersection of polyhedra 1 and 2
4. Store the constraints and the generators in an array (I convert all 
coefficients to doubles)

This process costs 100 seconds for 30000 calculations (so 30 
intersections per second) on a 600MHz machine.

When I remove step 3 (so I skip the intersection), the calculation takes 
about the same amount of time. So, the intersection is not the time 
consuming step. But removing step 1 and/or 2 speeds up the calculation 
significantly! So I might conclude that the ph.add_generator(ax+by+cz) 
is very slow.

My questions are now:

- is add_generator slow indeed?
- How can I speed up the code?

Thank you for your help!

Martin Rohde