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Trac #18157: Random failure in coerce_action.pyx
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Zmod(6) can be collected at the wrong time
{{{
sage -t --long --warn-long 47.9 src/sage/structure/coerce_actions.pyx
**********************************************************************
File "src/sage/structure/coerce_actions.pyx", line 78, in
sage.structure.coerce_actions.LAction
Failed example:
    sage.structure.coerce_actions.GenericAction(QQ, Zmod(6), True,
check=False)
Expected:
    Left action by Rational Field on Ring of integers modulo 6
Got:
    <repr(<sage.structure.coerce_actions.GenericAction at
0x7f8650aca938>) failed: RuntimeError: This action acted on a set that
became garbage collected>
**********************************************************************
1 item had failures:
   1 of   4 in sage.structure.coerce_actions.LAction
    [100 tests, 1 failure, 0.82 s]
}}}

Idem with
{{{
sage -t --long src/sage/structure/coerce.pyx
**********************************************************************
File "src/sage/structure/coerce.pyx", line 1452, in
sage.structure.coerce.CoercionModel_cache_maps.discover_action
Failed example:
    cm.discover_action(GF(5)['x'], ZZ, operator.div)
Expected:
    Right inverse action by Finite Field of size 5 on Univariate
Polynomial Ring in x over Finite Field of size 5
    with precomposition on right by Natural morphism:
      From: Integer Ring
      To:   Finite Field of size 5
Got:
    <repr(<sage.categories.action.PrecomposedAction at 0x2b41eb2a2050>)
failed: RuntimeError: This action acted on a set that became garbage
collected>
**********************************************************************
}}}

URL: http://trac.sagemath.org/18157
Reported by: vbraun
Ticket author(s): Vincent Delecroix, SImon King
Reviewer(s): Simon King
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@vbraun
Release Manager authored and vbraun committed Apr 18, 2015
2 parents e092901 + 60fcedc commit 217f9e6
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Showing 2 changed files with 173 additions and 59 deletions.
76 changes: 49 additions & 27 deletions src/sage/structure/coerce.pyx
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Expand Up @@ -238,7 +238,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
sage: from sage.structure.coerce import CoercionModel_cache_maps
sage: cm = CoercionModel_cache_maps(4, .95)
sage: A = cm.get_action(ZZ, NumberField(x^2-2, 'a'), operator.mul)
sage: K = NumberField(x^2-2, 'a')
sage: A = cm.get_action(ZZ, K, operator.mul)
sage: f, g = cm.coercion_maps(QQ, int)
sage: f, g = cm.coercion_maps(ZZ, int)
Expand Down Expand Up @@ -475,7 +476,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Result lives in Rational Field
Rational Field
sage: cm.explain(ZZ['x'], QQ)
sage: R = ZZ['x']
sage: cm.explain(R, QQ)
Action discovered.
Right scalar multiplication by Rational Field on Univariate Polynomial Ring in x over Integer Ring
Result lives in Univariate Polynomial Ring in x over Rational Field
Expand All @@ -501,10 +503,11 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Sometimes with non-sage types there is not enough information to deduce
what will actually happen::
sage: cm.explain(RealField(100), float, operator.add)
sage: R100 = RealField(100)
sage: cm.explain(R100, float, operator.add)
Right operand is numeric, will attempt coercion in both directions.
Unknown result parent.
sage: parent(RealField(100)(1) + float(1))
sage: parent(R100(1) + float(1))
<type 'float'>
sage: cm.explain(QQ, float, operator.add)
Right operand is numeric, will attempt coercion in both directions.
Expand All @@ -520,7 +523,9 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Result lives in Rational Field
Rational Field
sage: cm.explain(ZZ['x'], QQ['x'], operator.div)
sage: ZZx = ZZ['x']
sage: QQx = QQ['x']
sage: cm.explain(ZZx, QQx, operator.div)
Coercion on left operand via
Ring morphism:
From: Univariate Polynomial Ring in x over Integer Ring
Expand All @@ -542,7 +547,7 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Result lives in Rational Field
Rational Field
sage: cm.explain(ZZ['x'], ZZ, operator.div)
sage: cm.explain(ZZx, ZZ, operator.div)
Action discovered.
Right inverse action by Rational Field on Univariate Polynomial Ring in x over Integer Ring
with precomposition on right by Natural morphism:
Expand Down Expand Up @@ -582,7 +587,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
EXAMPLES::
sage: cm = sage.structure.element.get_coercion_model()
sage: steps, res = cm.analyse(GF(7), ZZ)
sage: GF7 = GF(7)
sage: steps, res = cm.analyse(GF7, ZZ)
sage: print steps
['Coercion on right operand via', Natural morphism:
From: Integer Ring
Expand Down Expand Up @@ -690,23 +696,29 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Rational Field
sage: cm.common_parent(ZZ, QQ, RR)
Real Field with 53 bits of precision
sage: cm.common_parent(ZZ[['T']], QQ['T'], RDF)
sage: ZZT = ZZ[['T']]
sage: QQT = QQ['T']
sage: cm.common_parent(ZZT, QQT, RDF)
Power Series Ring in T over Real Double Field
sage: cm.common_parent(4r, 5r)
<type 'int'>
sage: cm.common_parent(int, float, ZZ)
<type 'float'>
sage: cm.common_parent(*[RealField(prec) for prec in [10,20..100]])
sage: real_fields = [RealField(prec) for prec in [10,20..100]]
sage: cm.common_parent(*real_fields)
Real Field with 10 bits of precision
There are some cases where the ordering does matter, but if a parent
can be found it is always the same::
sage: cm.common_parent(QQ['x,y'], QQ['y,z']) == cm.common_parent(QQ['y,z'], QQ['x,y'])
sage: QQxy = QQ['x,y']
sage: QQyz = QQ['y,z']
sage: cm.common_parent(QQxy, QQyz) == cm.common_parent(QQyz, QQxy)
True
sage: cm.common_parent(QQ['x,y'], QQ['y,z'], QQ['z,t'])
sage: QQzt = QQ['z,t']
sage: cm.common_parent(QQxy, QQyz, QQzt)
Multivariate Polynomial Ring in x, y, z, t over Rational Field
sage: cm.common_parent(QQ['x,y'], QQ['z,t'], QQ['y,z'])
sage: cm.common_parent(QQxy, QQzt, QQyz)
Traceback (most recent call last):
...
TypeError: no common canonical parent for objects with parents: 'Multivariate Polynomial Ring in x, y over Rational Field' and 'Multivariate Polynomial Ring in z, t over Rational Field'
Expand Down Expand Up @@ -741,13 +753,17 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Rational Field
sage: cm.division_parent(QQ)
Rational Field
sage: cm.division_parent(ZZ['x'])
sage: ZZx = ZZ['x']
sage: cm.division_parent(ZZx)
Fraction Field of Univariate Polynomial Ring in x over Integer Ring
sage: cm.division_parent(GF(41))
sage: K = GF(41)
sage: cm.division_parent(K)
Finite Field of size 41
sage: cm.division_parent(Integers(100))
sage: Zmod100 = Integers(100)
sage: cm.division_parent(Zmod100)
Ring of integers modulo 100
sage: cm.division_parent(SymmetricGroup(5))
sage: S5 = SymmetricGroup(5)
sage: cm.division_parent(S5)
Symmetric group of order 5! as a permutation group
"""
try:
Expand Down Expand Up @@ -1081,7 +1097,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
sage: print g
None
sage: f, g = cm.coercion_maps(ZZ['x'], QQ)
sage: ZZx = ZZ['x']
sage: f, g = cm.coercion_maps(ZZx, QQ)
sage: print f
(map internal to coercion system -- copy before use)
Ring morphism:
Expand All @@ -1093,7 +1110,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
From: Rational Field
To: Univariate Polynomial Ring in x over Rational Field
sage: cm.coercion_maps(QQ, GF(7)) is None
sage: K = GF(7)
sage: cm.coercion_maps(QQ, K) is None
True
Note that to break symmetry, if there is a coercion map in both
Expand Down Expand Up @@ -1247,7 +1265,8 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Otherwise, try and compute an appropriate cover::
sage: cm.discover_coercion(ZZ['x,y'], RDF)
sage: ZZxy = ZZ['x,y']
sage: cm.discover_coercion(ZZxy, RDF)
((map internal to coercion system -- copy before use)
Call morphism:
From: Multivariate Polynomial Ring in x, y over Integer Ring
Expand Down Expand Up @@ -1306,24 +1325,26 @@ cdef class CoercionModel_cache_maps(CoercionModel):
EXAMPLES::
sage: cm = sage.structure.element.get_coercion_model()
sage: cm.get_action(ZZ['x'], ZZ, operator.mul)
sage: ZZx = ZZ['x']
sage: cm.get_action(ZZx, ZZ, operator.mul)
Right scalar multiplication by Integer Ring on Univariate Polynomial Ring in x over Integer Ring
sage: cm.get_action(ZZ['x'], ZZ, operator.imul)
sage: cm.get_action(ZZx, ZZ, operator.imul)
Right scalar multiplication by Integer Ring on Univariate Polynomial Ring in x over Integer Ring
sage: cm.get_action(ZZ['x'], QQ, operator.mul)
sage: cm.get_action(ZZx, QQ, operator.mul)
Right scalar multiplication by Rational Field on Univariate Polynomial Ring in x over Integer Ring
sage: cm.get_action(QQ['x'], int, operator.mul)
sage: QQx = QQ['x']
sage: cm.get_action(QQx, int, operator.mul)
Right scalar multiplication by Integer Ring on Univariate Polynomial Ring in x over Rational Field
with precomposition on right by Native morphism:
From: Set of Python objects of type 'int'
To: Integer Ring
sage: R.<x> = QQ['x']
sage: A = cm.get_action(R, ZZ, operator.div); A
sage: A = cm.get_action(QQx, ZZ, operator.div); A
Right inverse action by Rational Field on Univariate Polynomial Ring in x over Rational Field
with precomposition on right by Natural morphism:
From: Integer Ring
To: Rational Field
sage: x = QQx.gen()
sage: A(x+10, 5)
1/5*x + 2
Expand Down Expand Up @@ -1448,12 +1469,13 @@ cdef class CoercionModel_cache_maps(CoercionModel):
Bug :trac:`17740`::
sage: cm.discover_action(GF(5)['x'], ZZ, operator.div)
sage: R = GF(5)['x']
sage: cm.discover_action(R, ZZ, operator.div)
Right inverse action by Finite Field of size 5 on Univariate Polynomial Ring in x over Finite Field of size 5
with precomposition on right by Natural morphism:
From: Integer Ring
To: Finite Field of size 5
sage: cm.bin_op(GF(5)['x'].gen(), 7, operator.div).parent()
sage: cm.bin_op(R.gen(), 7, operator.div).parent()
Univariate Polynomial Ring in x over Finite Field of size 5
"""
#print "looking", R, <int><void *>R, op, S, <int><void *>S
Expand Down

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