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#10147 closed defect (fixed)

conversions of constant polynomials

Reported by:	mmezzarobba	Owned by:	AlexGhitza
Priority:	major	Milestone:	sage-9.3
Component:	algebra	Keywords:
Cc:	jason	Merged in:
Authors:	Vincent Delecroix	Reviewers:	Matthias Koeppe
Report Upstream:	N/A	Work issues:
Branch:	6822948 (Commits, GitHub, GitLab)	Commit:	6822948572e9dcb87e86fa30f3387e640c88c55b
Dependencies:		Stopgaps:

Status badges

Description (last modified by vdelecroix)

Many conversions of constant polynomials fail

sage: CC(QQ['x']['y'](2/3))
Traceback (most recent call last):
...
TypeError: unable to coerce to a ComplexNumber:
<class 'sage.rings.polynomial.polynomial_element.Polynomial_generic_dense'>

As a consequence, some root computations are not available

sage: R.<x> = QQ['y'][]
sage: (-x+1).roots(ring=CC)
[(1.00000000000000, 1)]
sage: (-1/2*x+1).roots(ring=CC)
Traceback (most recent call last):
...
TypeError: unable to coerce to a ComplexNumber:
<class 'sage.rings.polynomial.polynomial_element.Polynomial_generic_dense'>

(this used to crash on older version of SageMath, see below).

Original report on previous version of sage

p.roots(ring=CC) where p is an element QQ['y']['x'] whose coefficient do not depend on y leads to several different errors depending on the value of p. I guess there are in fact several distinct issues. The final crash might be related to #9826.

~$ sage
----------------------------------------------------------------------
| Sage Version 4.5.3, Release Date: 2010-09-04                       |
| Type notebook() for the GUI, and license() for information.        |
----------------------------------------------------------------------
sage: R.<x> = QQ['y'][]
sage: (-x+1).roots(ring=CC)
[(1.00000000000000, 1)]
sage: (-1/2*x+1).roots(ring=CC)
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (19469, 0))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/home/marc/<ipython console> in <module>()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_element.so in sage.rings.polynomial.polynomial_element.Polynomial.roots (sage/rings/polynomial/polynomial_element.c:31226)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_element.so in sage.rings.polynomial.polynomial_element.Polynomial.change_ring (sage/rings/polynomial/polynomial_element.c:16456)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__ (sage/structure/parent.c:6407)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/coerce_maps.so in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (sage/structure/coerce_maps.c:3108)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/coerce_maps.so in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (sage/structure/coerce_maps.c:3010)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_ring.pyc in _element_constructor_(self, x, check, is_gen, construct, **kwds)
    311                 x = x.Polrev()
    312 
--> 313         return C(self, x, check, is_gen, construct=construct, **kwds)
    314 
    315     def is_integral_domain(self, proof = True):

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_real_mpfr_dense.so in sage.rings.polynomial.polynomial_real_mpfr_dense.PolynomialRealDense.__init__ (sage/rings/polynomial/polynomial_real_mpfr_dense.c:3609)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__ (sage/structure/parent.c:6407)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/coerce_maps.so in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (sage/structure/coerce_maps.c:3108)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/coerce_maps.so in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (sage/structure/coerce_maps.c:3010)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/real_mpfr.so in sage.rings.real_mpfr.RealField_class._element_constructor_ (sage/rings/real_mpfr.c:5058)()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/real_mpfr.so in sage.rings.real_mpfr.RealNumber._set (sage/rings/real_mpfr.c:8767)()

TypeError: Unable to convert x (='-1/2') to real number.
sage: (-1/2*x+1/2).roots()
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)

/home/marc/<ipython console> in <module>()

/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_element.so in sage.rings.polynomial.polynomial_element.Polynomial.roots (sage/rings/polynomial/polynomial_element.c:31591)()

NotImplementedError: root finding for this polynomial not implemented
sage: (-1/2*x+1/2).roots(ring=CC)
*** glibc detected *** python: munmap_chunk(): invalid pointer: 0x0000000001208958 ***
======= Backtrace: =========
/lib/libc.so.6[0x3c38271ad6]
/home/marc/opt/sage-4.5.3/local/lib/libmpfr.so.1(mpfr_clear+0x45)[0x7fc911f80a45]
/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_real_mpfr_dense.so(+0x7867)[0x7fc90a74d867]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(+0xa241c)[0x7fc91e85841c]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x3af3)[0x7fc91e89f973]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(+0x730df)[0x7fc91e8290df]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(+0x5819f)[0x7fc91e80e19f]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/coerce_maps.so(+0x12724)[0x7fc910609724]
/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/structure/parent.so(+0x25ec2)[0x7fc9174a2ec2]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(+0xaba8c)[0x7fc91e861a8c]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_element.so(+0xd3c2)[0x7fc90bc873c2]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyObject_Call+0x53)[0x7fc91e7fce13]
/home/marc/opt/sage-4.5.3/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_element.so(+0xd191c)[0x7fc90bd4b91c]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5a8e)[0x7fc91e8a190e]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCode+0x32)[0x7fc91e8a2df2]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x6244)[0x7fc91e8a20c4]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5235)[0x7fc91e8a10b5]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5235)[0x7fc91e8a10b5]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5ab2)[0x7fc91e8a1932]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5235)[0x7fc91e8a10b5]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5235)[0x7fc91e8a10b5]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalFrameEx+0x5235)[0x7fc91e8a10b5]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCodeEx+0x8cd)[0x7fc91e8a2d1d]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyEval_EvalCode+0x32)[0x7fc91e8a2df2]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyRun_FileExFlags+0xb0)[0x7fc91e8c2c90]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(PyRun_SimpleFileExFlags+0xdc)[0x7fc91e8c2e5c]
/home/marc/opt/sage-4.5.3/local/lib/libpython2.6.so.1.0(Py_Main+0xb36)[0x7fc91e8d0186]
/lib/libc.so.6(__libc_start_main+0xfd)[0x3c3821ec4d]
python[0x400699]
======= Memory map: ========
00400000-00401000 r-xp 00000000 08:0a 1787644                            /home/marc/opt/sage-4.5.3/local/bin/python
00600000-00601000 rw-p 00000000 08:0a 1787644                            /home/marc/opt/sage-4.5.3/local/bin/python
00cb1000-05306000 rw-p 00000000 00:00 0                                  [heap]
32b2c00000-32b2c16000 r-xp 00000000 08:06 40741                          /lib/libgcc_s.so.1
32b2c16000-32b2e15000 ---p 00016000 08:06 40741                          /lib/libgcc_s.so.1
32b2e15000-32b2e16000 rw-p 00015000 08:06 40741                          /lib/libgcc_s.so.1
3c37e00000-3c37e1e000 r-xp 00000000 08:06 40724                          /lib/ld-2.11.2.so
3c3801d000-3c3801e000 r--p 0001d000 08:06 40724                          /lib/ld-2.11.2.so
3c3801e000-3c3801f000 rw-p 0001e000 08:06 40724                          /lib/ld-2.11.2.so
3c3801f000-3c38020000 rw-p 00000000 00:00 0 
3c38200000-3c38358000 r-xp 00000000 08:06 40737                          /lib/libc-2.11.2.so
3c38358000-3c38557000 ---p 00158000 08:06 40737                          /lib/libc-2.11.2.so
3c38557000-3c3855b000 r--p 00157000 08:06 40737                          /lib/libc-2.11.2.so
3c3855b000-3c3855c000 rw-p 0015b000 08:06 40737                          /lib/libc-2.11.2.so
3c3855c000-3c38561000 rw-p 00000000 00:00 0 
3c38600000-3c38680000 r-xp 00000000 08:06 40787                          /lib/libm-2.11.2.so
3c38680000-3c38880000 ---p 00080000 08:06 40787                          /lib/libm-2.11.2.so
3c38880000-3c38881000 r--p 00080000 08:06 40787                          /lib/libm-2.11.2.so
3c38881000-3c38882000 rw-p 00081000 08:06 40787                          /lib/libm-2.11.2.so
3c38a00000-3c38a02000 r-xp 00000000 08:06 40738                          /lib/libdl-2.11.2.so
3c38a02000-3c38c02000 ---p 00002000 08:06 40738                          /lib/libdl-2.11.2.so
3c38c02000-3c38c03000 r--p 00002000 08:06 40738                          /lib/libdl-2.11.2.so
3c38c03000-3c38c04000 rw-p 00003000 08:06 40738                          /lib/libdl-2.11.2.so
3c38e00000-3c38e17000 r-xp 00000000 08:06 40766                          /lib/libpthread-2.11.2.so
3c38e17000-3c39016000 ---p 00017000 08:06 40766                          /lib/libpthread-2.11.2.so
3c39016000-3c39017000 r--p 00016000 08:06 40766                          /lib/libpthread-2.11.2.so
3c39017000-3c39018000 rw-p 00017000 08:06 40766                          /lib/libpthread-2.11.2.so
3c39018000-3c3901c000 rw-p 00000000 00:00 0 
3c4ba00000-3c4ba08000 r-xp 00000000 08:06 40917                          /lib/libcrypt-2.11.2.so
3c4ba08000-3c4bc07000 ---p 00008000 08:06 40917                          /lib/libcrypt-2.11.2.so
3c4bc07000-3c4bc08000 r--p 00007000 08:06 40917                          /lib/libcrypt-2.11.2.so
3c4bc08000-3c4bc09000 rw-p 00008000 08:06 40917                          /lib/libcrypt-2.11.2.so

Change History (21)

comment:1 Changed 11 years ago by jason

Cc jason added

comment:2 Changed 8 years ago by jdemeyer

Milestone changed from sage-5.11 to sage-5.12

comment:3 Changed 8 years ago by vbraun_spam

Milestone changed from sage-6.1 to sage-6.2

comment:4 Changed 8 years ago by vbraun_spam

Milestone changed from sage-6.2 to sage-6.3

comment:5 Changed 7 years ago by vbraun_spam

Milestone changed from sage-6.3 to sage-6.4

comment:6 Changed 9 months ago by mmezzarobba

Milestone changed from sage-6.4 to sage-duplicate/invalid/wontfix
Status changed from new to needs_review

No longer crashes; the errors in the cases that are not implemented make sense; I doubt this is worth adding tests.

comment:7 Changed 9 months ago by vdelecroix

In sage-9.3.beta7 the example fails because of

sage: RR(QQ['y'](-1/2)) 
Traceback (most recent call last):
...
TypeError: unable to convert '-1/2' to a real number

which is worth fixing.

comment:8 Changed 9 months ago by vdelecroix

As a matter of comparison, it works in QQ

sage: R.<x> = QQ['y'][]
sage: (-1/2*x+1).roots(ring=QQ)
[(2, 1)]

This is because the conversion works

sage: QQ(QQ['y'](1/2))
1/2

This is explained by the fact that the conversion method _rational_ is implemented on polynomial

sage: QQ['x'](1/2)._rational_()
1/2

It is worth adding the corresponding conversion methods for floating point numbers

_mpfr_ for RealField
_real_mpfi_ for RealIntervalField

Though, complex numbers do not have a conversion method (set in the constructor via self._populate_coercion_lists_(convert_method_name='XXX')).

comment:9 Changed 9 months ago by vdelecroix

Milestone changed from sage-duplicate/invalid/wontfix to sage-9.4
Status changed from needs_review to needs_info

comment:10 Changed 9 months ago by vdelecroix

Authors set to Vincent Delecroix
Branch set to u/vdelecroix/10147
Commit set to 4c7a3c3066ed34c65a22d722aa9c47e717bf6c6e
Status changed from needs_info to needs_review

New commits:

ee49837	`add convert method for ComplexField`
4c7a3c3	`more scalar conversions for polynomials`

comment:11 Changed 9 months ago by vdelecroix

Description modified (diff)
Summary changed from Inconsistent behaviour of p.roots(ring=CC) for p(x) in QQ['y']['x'] (incl. crashing) to conversions of constant polynomials

comment:12 Changed 9 months ago by vdelecroix

Description modified (diff)

comment:13 follow-up: ↓ 14 Changed 9 months ago by mkoeppe

Status changed from needs_review to needs_work

Patchbot shows doctest errors

comment:14 in reply to: ↑ 13 Changed 9 months ago by vdelecroix

Status changed from needs_work to needs_review

Replying to mkoeppe:

Patchbot shows doctest errors

which one?

comment:15 Changed 9 months ago by mkoeppe

This one https://patchbot.sagemath.org/log/10147/Linux/1_SMP_Debian_4.19.171-2_(2021-01-30)/x86_64/4.19.0-14-amd64/tmonteil-lxc3/2021-03-17%2017:45:45

comment:16 Changed 9 months ago by vdelecroix

Status changed from needs_review to needs_work

thx

comment:17 Changed 9 months ago by git

Commit changed from 4c7a3c3066ed34c65a22d722aa9c47e717bf6c6e to 6822948572e9dcb87e86fa30f3387e640c88c55b

Branch pushed to git repo; I updated commit sha1. New commits:

6822948 fix doctests

comment:18 Changed 9 months ago by vdelecroix

Status changed from needs_work to needs_review

comment:19 Changed 9 months ago by mkoeppe

Reviewers set to Matthias Koeppe
Status changed from needs_review to positive_review

LGTM

comment:20 Changed 9 months ago by vbraun

Branch changed from u/vdelecroix/10147 to 6822948572e9dcb87e86fa30f3387e640c88c55b
Resolution set to fixed
Status changed from positive_review to closed

comment:21 Changed 9 months ago by mkoeppe

Milestone changed from sage-9.4 to sage-9.3

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