#18221 closed defect (fixed)
x / 2 doesn't work for x generator of free Qalgebra
Reported by:  darij  Owned by:  

Priority:  major  Milestone:  sage6.7 
Component:  coercion  Keywords:  coercion, sd67, 
Cc:  tscrim, SimonKing, nthiery, robertwb, vdelecroix  Merged in:  
Authors:  Travis Scrimshaw  Reviewers:  Nicolas M. Thiéry 
Report Upstream:  N/A  Work issues:  
Branch:  9b14aa5 (Commits, GitHub, GitLab)  Commit:  
Dependencies:  Stopgaps: 
Description
sage: R.<x> = FreeAlgebra(QQ) sage: x/2  RuntimeError Traceback (most recent call last) <ipythoninput2749cf4ad628f> in <module>() > 1 x/Integer(2) /home/skraeling/sage/src/sage/structure/element.pyx in sage.structure.element.RingElement.__div__ (build/cythonized/sage/structure/element.c:18393)() 1955 return (<RingElement>self)._div_(<RingElement>right) 1956 global coercion_model > 1957 return coercion_model.bin_op(self, right, div) 1958 1959 cpdef RingElement _div_(self, RingElement right): /home/skraeling/sage/src/sage/structure/coerce.pyx in sage.structure.coerce.CoercionModel_cache_maps.bin_op (build/cythonized/sage/structure/coerce.c:7628)() 849 if xp is yp: 850 return op(x,y) > 851 action = self.get_action(xp, yp, op, x, y) 852 if action is not None: 853 return (<Action>action)._call_(x, y) /home/skraeling/sage/src/sage/structure/coerce.pyx in sage.structure.coerce.CoercionModel_cache_maps.get_action (build/cythonized/sage/structure/coerce.c:13309)() 1334 pass 1335 action = self.discover_action(R, S, op, r, s) > 1336 action = self.verify_action(action, R, S, op) 1337 self._action_maps.set(R, S, op, action) 1338 return action /home/skraeling/sage/src/sage/structure/coerce.pyx in sage.structure.coerce.CoercionModel_cache_maps.verify_action (build/cythonized/sage/structure/coerce.c:14389)() 1386 1387 if action.left_domain() is not R or action.right_domain() is not S: > 1388 raise RuntimeError, """There is a BUG in the coercion model: 1389 Action found for R %s S does not have the correct domains 1390 R = %s RuntimeError: There is a BUG in the coercion model: Action found for R <builtin function div> S does not have the correct domains R = Free Algebra on 1 generators (x,) over Rational Field S = Integer Ring (should be Free Algebra on 1 generators (x,) over Rational Field, Rational Field) action = Right inverse action by Rational Field on Free Algebra on 1 generators (x,) over Rational Field (<type 'sage.categories.action.InverseAction'>)
Change History (24)
comment:1 Changed 6 years ago by
 Cc tscrim SimonKing nthiery added
comment:2 Changed 6 years ago by
comment:3 Changed 6 years ago by
I am using 6.7.beta1.
comment:4 Changed 6 years ago by
This fails is 6.6.rc2 as well.
comment:5 Changed 6 years ago by
The only changes since 6.6.beta4 in src/structure
are in parent from #17981 and in element.pyx
:
include "sage/ext/stdsage.pxi" include "sage/ext/python.pxi" include "coerce.pxi" +from sage.ext.stdsage cimport *
I'd be very surprised if the change I made in #17981 broke this.
EDIT  Oh, thats 6.5.beta4...
comment:6 Changed 6 years ago by
Note that in the error message it says:
RuntimeError: There is a BUG in the coercion model: Action found for R <builtin function div> S does not have the correct domains R = Free Algebra on 1 generators (x,) over Rational Field S = Integer Ring (should be Free Algebra on 1 generators (x,) over Rational Field, Rational Field)
Hence, for a change we do not have the problem of nonunique unique parents or parents that have prematurely been garbage collected, but we have a genuinely wrong domain. The coercion model expects rational field but gets integer ring.
comment:7 Changed 6 years ago by
Okay, so from 6.5.beta4, the only nontrivial changes to coerce_action.pyx
are in using isinstance
instead of PY_TYPE_CHECK
and adding an __invert__
method to ModuleAction
.
comment:8 Changed 6 years ago by
I'd guess this came from the changes of #17740 from looking at the diff.
comment:9 Changed 6 years ago by
 Branch set to public/coercion/fix_actions18221
 Commit set to dce923e806cdd021b1b0f5a427870cf76f7bed6e
 Status changed from new to needs_review
comment:10 Changed 6 years ago by
 Cc robertwb added
 Reviewers set to Nicolas Thiéry
comment:11 Changed 6 years ago by
 Commit changed from dce923e806cdd021b1b0f5a427870cf76f7bed6e to 6b2e9bbd832fdd672e6b5b36e457926305ce482d
Branch pushed to git repo; I updated commit sha1. New commits:
6b2e9bb  Added test which checks the action map.

comment:12 Changed 6 years ago by
 Status changed from needs_review to positive_review
Nicolas looked over the code on my computer and gave it an okay.
comment:13 Changed 6 years ago by
 Status changed from positive_review to needs_review
comment:14 Changed 6 years ago by
Sorry, I misexpressed myself: this looks good to me, but I would not mind having a quick double check by the authors of #17740.
comment:15 Changed 6 years ago by
 Cc vdelecroix added
comment:16 Changed 6 years ago by
Hello,
In the doc I would not write Bug :trac:`18221`
. It looks like there is a problem, but your are actually checking that there is none. Beyond this trivial comment, I am sorry that we broke that in #17740. And the fix looks like the good one to me.
Vincent
comment:17 Changed 6 years ago by
 Commit changed from 6b2e9bbd832fdd672e6b5b36e457926305ce482d to 9b14aa5fcf1684960c93984ef74860d6c26cb1ac
Branch pushed to git repo; I updated commit sha1. New commits:
9b14aa5  Change in docstring.

comment:18 Changed 6 years ago by
I had just copied the message added in #17740, so I changed that docstring too.
comment:19 Changed 6 years ago by
Is this pos_rev then?
comment:20 Changed 6 years ago by
ok for me at least
comment:21 Changed 6 years ago by
 Status changed from needs_review to positive_review
comment:22 Changed 6 years ago by
Assuming all tests pass, that's good to go!
comment:23 Changed 6 years ago by
 Branch changed from public/coercion/fix_actions18221 to 9b14aa5fcf1684960c93984ef74860d6c26cb1ac
 Resolution set to fixed
 Status changed from positive_review to closed
comment:24 Changed 6 years ago by
 Commit 9b14aa5fcf1684960c93984ef74860d6c26cb1ac deleted
 Reviewers changed from Nicolas Thiéry to Nicolas M. Thiéry
What is the problem?
EDIT: I mean, what version are you using?