piplib doesn't terminate(?) till memory exhaustion

[Uday Bondhugula]

I'm using the git version of piplib (current tip of master - commit
c430380bd7080af6773392736a5ac571921c0bd2). For this input, piplib (64-bit version) seems to run forever (at least till I run out of memory).

(no parameters).

17 17
 0 0 0 0 1 0 0 0 0 0 -1 0 0 0 0 0 0
 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 -3
 0 0 0 0 0 0 1 0 0 0 0 0 -1 0 0 0 0
 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 -2
 1 -1 -1 0 0 0 0 1 1 0 0 0 0 0 0 0 -1
 1 0 0 0 0 0 0 0 0 20 -2 0 -1 0 0 0 18
 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
 1 0 0 0 0 0 0 0 0 0 -1 0 0 0 1 0 -1
 1 0 0 0 0 0 0 0 0 0 0 0 -1 1 0 0 -2
 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 -3
 1 25 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 24
 1 0 0 0 0 0 0 -25 0 0 1 0 0 0 0 0 0
 1 0 10 0 0 0 0 0 0 0 -1 0 0 0 0 0 8
 1 0 0 0 0 0 0 0 -20 0 2 0 0 0 0 0 3
 1 0 0 -20 0 0 0 0 0 0 2 0 1 0 0 0 0
 1 0 0 20 0 0 0 0 0 0 -2 0 -1 0 0 0 19
 1 0 0 0 0 0 0 0 0 -20 2 0 1 0 0 0 1

To reproduce, run example/example64, and input

0 2

-1

<followed by the above matrix>

~ Uday

[Sven Verdoolaege]

On Fri, Jul 26, 2013 at 12:11:56AM -0700, Uday K Bondhugula wrote:
> 17 17
> 0 0 0 0 1 0 0 0 0 0 -1 0 0 0 0 0 0
> 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 -3
> 0 0 0 0 0 0 1 0 0 0 0 0 -1 0 0 0 0
> 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 -2
> 1 -1 -1 0 0 0 0 1 1 0 0 0 0 0 0 0 -1
> 1 0 0 0 0 0 0 0 0 20 -2 0 -1 0 0 0 18
> 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
> 1 0 0 0 0 0 0 0 0 0 -1 0 0 0 1 0 -1
> 1 0 0 0 0 0 0 0 0 0 0 0 -1 1 0 0 -2
> 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 -3
> 1 25 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 24
> 1 0 0 0 0 0 0 -25 0 0 1 0 0 0 0 0 0
> 1 0 10 0 0 0 0 0 0 0 -1 0 0 0 0 0 8
> 1 0 0 0 0 0 0 0 -20 0 2 0 0 0 0 0 3
> 1 0 0 -20 0 0 0 0 0 0 2 0 1 0 0 0 0
> 1 0 0 20 0 0 0 0 0 0 -2 0 -1 0 0 0 19
> 1 0 0 0 0 0 0 0 0 -20 2 0 1 0 0 0 1

In my experience, the PIP algorithm generally has a difficult
time on such empty polyhedra. You may want to check if your
input is empty first before trying to compute its minimal
element.

skimo