is_globally_equivalent_to is not symmetric

[simonbrandhorst]

Q = QuadraticForm(ZZ, 2, [2,3,5])
P = QuadraticForm(ZZ, 2, [8,6,5])
Q.is_globally_equivalent_to(P)
True
P.is_globally_equivalent_to(Q)
False

The expected output in any case is False.
The underlying computation is done with Pari.

Upstream ticket (PARI):

• PARI bug #2140: Bug: qfisom not symmetric

Upstream: Fixed upstream, in a later stable release.

CC: @slel @orlitzky @kliem

Component: quadratic forms

Keywords: pari

Author: Simon Brandhorst

Branch: be9f880

Reviewer: Samuel Lelièvre

Issue created by migration from https://trac.sagemath.org/ticket/27749

[simonbrandhorst]

Changed upstream from Reported upstream. No feedback yet. to Reported upstream. Developers acknowledge bug.

[slel]

Changed upstream from Reported upstream. Developers acknowledge bug. to Fixed upstream, but not in a stable release.

[slel]

Changed keywords from none to pari

[embray]

comment:3

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).

[fchapoton]

comment:4

This is still failing in pari 2.11.2 from May 2019 (currently in sage)

but works in pari [2, 11, 4, 23175, "e4f812ce9f"].

This will need a doctest once pari is updated.

[mkoeppe]

comment:7

See also discussion in #29472

[simonbrandhorst]

comment:8

sage: Q = QuadraticForm(ZZ, 2, [2,3,5]) 
....: P = QuadraticForm(ZZ, 2, [8,6,5]) 
....: Q.is_globally_equivalent_to(P)                                         
False
sage: P.is_globally_equivalent_to(Q)                                         
False
sage: pari.version()                                                         
(2, 11, 4)

[slel]

comment:9

The pari upgrade happened in

• Upgrade to pari 2.11.4 #29313: Upgrade to pari 2.11.4

which was merged in Sage 9.2.beta7.

[slel]

Changed upstream from Fixed upstream, but not in a stable release. to Fixed upstream, in a later stable release.

[slel]

comment:10

Can someone add the doctest?

[simonbrandhorst]

Branch: u/sbrandhorst/is_globally_equivalent_to_is_not_symmetric

[simonbrandhorst]

Commit: be9f880

[simonbrandhorst]

New commits:

be9f880

document that the bug in equivalence testing is fixed

[slel]

Reviewer: Samuel Lelièvre

[slel]

Author: Simon Brandhorst

[vbraun]

Changed branch from u/sbrandhorst/is_globally_equivalent_to_is_not_symmetric to be9f880

[dimpase]

comment:15

Shouldn't a test be added to spkg-configure.m4 of pari? Note that e.g. on Fedora 30 one has pari/gp version 2.11.2, which passes all the tests we currently have there, but fails the test in
quadratic_form__equivalence_testing added by this ticket?

[dimpase]

Changed commit from be9f880 to none

[dimpase]

comment:16

Replying to @dimpase:

Shouldn't a test be added to spkg-configure.m4 of pari? Note that e.g. on Fedora 30 one has pari/gp version 2.11.2, which passes all the tests we currently have there, but fails the test in
quadratic_form__equivalence_testing added by this ticket?

should be fixed by #30800