Fix missing uniqueness of parents when unpickling libsingular polynomial rings

[simon-king-jena]

First session:

sage: P.<foo,bar> = PolynomialRing(QQ)
sage: save(P,'tmp')

Second session:

sage: Q = load('tmp.sobj')
sage: P.<foo,bar> = PolynomialRing(QQ)
sage: Q is P
False
sage: Q2 = load('tmp.sobj')
sage: Q2 is P
True
sage: Q2 is Q
False

That is fixed with the attached patch.

CC: @malb

Component: pickling

Keywords: unpickle libsingular unique parents

Author: Simon King

Reviewer: Martin Albrecht, Volker Braun

Merged: sage-4.8.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/11911

[simon-king-jena]

comment:2

Remark: I consider it a feature of my patch that old pickles of polynomial rings will automatically be transformed into a new format, should Sage ever drop libsingular.

[malb]

Reviewer: Martin Albrecht

[malb]

comment:3

Patch looks good so I'll give it a positive review. In case doctests break (didn't run any) it can be reverted.

[jdemeyer]

comment:4

Please fix this comment, I believe it contains at least three mistakes :-)

# If future Sage versions remove libsingular by a different implementation,
# the unpickled ring will be long the the new implementation.

[simon-king-jena]

Preserve uniqueness of parents when unpickling a libsingular polynomial ring

[simon-king-jena]

comment:7

Attachment: trac11911_libsingular_pickling.patch.gz

I replaced the patch. If you think the comment is now fine, then reinstate the positive review please.

[vbraun]

Changed reviewer from Martin Albrecht to Martin Albrecht, Volker Braun

[vbraun]

comment:8

That comment still won't win the Nobel price in literature, but at least I get what is meant. Applies fine to sage-4.7.2.rc0. Positive review.

[vbraun]

Author: Simon King

[jdemeyer]

Merged: sage-4.7.3.alpha1

[jdemeyer]

Milestone sage-4.7.3 deleted

[jdemeyer]

Changed merged from sage-4.7.3.alpha1 to sage-4.8.alpha1