[PPL-devel] integer versus rational solutions

[Konrad Trifunovic]

Hi all,

the other tip that I give: if I try to resolve the same polyhedron,
but if I make it Closed Polyhedron, then the solver 'contains_integer_point'
runs out of memory.

Konrad

2009/7/10 Konrad Trifunovic <konrad.trifunovic at gmail.com>:
> Hi all,
>
> here I attach an polyhedron of smaller dimensionality:
> I also ask for 'contains_integer_point'. It does not give me
> any result in reasonable time (actually I did not wait
> until it gives any result, since it took more than few minutes).
> I try it on 32-bit machine.
>
> Thanks,
> Konrad
>
>
>
>
> 2009/7/9 Konrad Trifunovic <konrad.trifunovic at gmail.com>:
>> Hi,
>>
>> that's a good point.
>> We DO NOT need NNC polyhedra. Closed Polyhedra are fine
>> (at least for dependence analysis). Do You think that using
>> C_Polyhedron would help us avoid the much of the complexity problems?
>>
>> from my analysis (by looking at the PPL code) I have seen
>> that the "contains_integer_point" methods call the MIP
>> (Mixed Integer Programming) routines, to solve the system of constraints.
>> I have seen that it behaves differently in the case of Convex and
>> NNC polyhedra.
>>
>> regards,
>> Konrad
>>
>> 2009/7/9 Roberto Bagnara <bagnara at cs.unipr.it>:
>>>
>>> Konrad Trifunovic wrote:
>>>> I attach a patch that uses 'integer existence test'.
>>>> I have forced the use of dependence check.
>>>
>>> Hi there.
>>>
>>> I am sorry if the answer is obvious, but I am wondering
>>> why you are using NNC polyhedra (NNC_Polyhedron) instead
>>> of ordinary polyhedra (C_Polyhedron).  Do you need to
>>> characterize rational solutions and use strict constraints?
>>> All the best,
>>>
>>>     Roberto
>>>
>>> --
>>> Prof. Roberto Bagnara
>>> Computer Science Group
>>> Department of Mathematics, University of Parma, Italy
>>> http://www.cs.unipr.it/~bagnara/
>>> mailto:bagnara at cs.unipr.it
>>>
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>>
>