[PPL-devel] PPL timings depend on sort (ordering) of input?

[Nestor Aguilera]

Hi,

I am new to PPL, coming from CDD (and PORTA), and I am using "ppl_lcdd" (replacing "lcdd_gmp").

I found PPL quite fast on my problems as compared to CDD, so I am quite happy with it.

However, working with circulant matrices I found that the timings depend very much on how the problem is presented.

I am enclosing two files with the same vertices: those in the "ppl_7.ext" are those in "ppl_1.ext" rotated by 6 places, and the problem is to find the inequalities description of the convex hull.

In my machine, "ppl_lcdd" takes about 1.2s to solve "ppl_1" and about 18.3s to solve "ppl_7", although they are essentially the same problem.

Can anyone tell me why this is so?, does it depend on any special sorting in the input?

Thank you very much.

                                               Néstor Aguilera

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