#11849: ppl.pyx test takes a very long time contrary to what is claimed
------------------------------+---------------------------------------------
Reporter: jdemeyer | Owner: was
Type: defect | Status: positive_review
Priority: blocker | Milestone: sage-4.7.2
Component: interfaces | Keywords: Parma Polyhedra Library
Work_issues: | Upstream: N/A
Reviewer: Jeroen Demeyer | Author: Volker Braun
Merged: | Dependencies:
------------------------------+---------------------------------------------
Changes (by jdemeyer):
* status: needs_review => positive_review
* reviewer: => Jeroen Demeyer
Old description:
> From the file {{{sage/libs/ppl.pyx}}} starting at line 112:
> {{{
> The computation finishes without noticeable delay on my desktop
> (timeit measures it to be 35msec). Cddlib needs about 3 minutes on the
> same hardware::
>
> sage: basis = range(0,6)
> sage: x = [ Variable(i) for i in basis ]
> sage: gs = [ tuple(coeff) for coeff in permutations(basis) ]
> sage: Polyhedron(vertices=gs) # long time
> A 5-dimensional polyhedron in QQ^6 defined as the convex hull of 720
> vertices.
> }}}
>
> Contrary to the claim that this takes milliseconds, it actually takes
> minutes. This regularly causes timeouts when testing Sage on Skynet.
>
> On sage.math.washington.edu, sage-4.7.2.alpha0:
> {{{
> sage: from sage.libs.ppl import Variable, Generator_System, point,
> C_Polyhedron
> sage: basis = range(0,6)
> sage: x = [ Variable(i) for i in basis ]
> sage: gs = [ tuple(coeff) for coeff in permutations(basis) ]
> sage: time Polyhedron(vertices=gs)
> A 5-dimensional polyhedron in QQ^6 defined as the convex hull of 720
> vertices.
>
> Time: CPU 0.14 s, Wall: 218.94 s
> }}}
>
> Personally I do not understand why this issue was not caught earlier, it
> looks like a [http://catb.org/jargon/html/S/schroedinbug.html
> schrödinbug] to me.
>
> See also: #10039, #11534.
>
> Apply [attachment:trac_11849_shorter_long_ppl_test.patch]
New description:
From the file {{{sage/libs/ppl.pyx}}} starting at line 112:
{{{
The computation finishes without noticeable delay on my desktop
(timeit measures it to be 35msec). Cddlib needs about 3 minutes on the
same hardware::
sage: basis = range(0,6)
sage: x = [ Variable(i) for i in basis ]
sage: gs = [ tuple(coeff) for coeff in permutations(basis) ]
sage: Polyhedron(vertices=gs) # long time
A 5-dimensional polyhedron in QQ^6 defined as the convex hull of 720
vertices.
}}}
Contrary to the claim that this takes milliseconds, it actually takes
minutes. This regularly causes timeouts when testing Sage on Skynet.
On sage.math.washington.edu, sage-4.7.2.alpha0:
{{{
sage: from sage.libs.ppl import Variable, Generator_System, point,
C_Polyhedron
sage: basis = range(0,6)
sage: x = [ Variable(i) for i in basis ]
sage: gs = [ tuple(coeff) for coeff in permutations(basis) ]
sage: time Polyhedron(vertices=gs)
A 5-dimensional polyhedron in QQ^6 defined as the convex hull of 720
vertices.
Time: CPU 0.14 s, Wall: 218.94 s
}}}
Personally I do not understand why this issue was not caught earlier, it
looks like a [http://catb.org/jargon/html/S/schroedinbug.html schrödinbug]
to me.
See also: #10039, #11534.
Apply [attachment:trac_11849_shorter_long_ppl_test.patch] and
[attachment:11849_reviewer.patch]
--
Comment:
positive_review modulo the reviewer patch.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11849#comment:5>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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