On Saturday, April 22, 2017 at 2:10:48 AM UTC+1, David Roe wrote:
>
>
>
> On Fri, Apr 21, 2017 at 11:29 AM, Dima Pasechnik <dim...@gmail.com
> <javascript:>> wrote:
>
>>
>>
>> On Friday, April 21, 2017 at 3:46:03 PM UTC+1, David Roe wrote:
>>>
>>> Quick guess (don't have time to look at this soon): the issue could be
>>> in the action discovery code, which may try creating elements of
>>> numpy.float32 using weird inputs. This could cause a difference between
>>> right and left multiplication. One way to check if this is the source is to
>>> try converting each of the polynomials from RR['x'].some_elements() into
>>> numpy.float32 and see if you get the same error.
>>>
>>
>> no, this does not give anything that looks like the error in question (no
>> errors on degree 0 terms,
>> "ValueError: setting an array element with a sequence." on degree >0
>> terms)
>>
>
> Sorry, I don't have any other ideas, and can't play around with it easily
> since the standard Sage build isn't producing these errors.
> David
>
>>
>>
Is there a "normal" way to trace all the coersion/conversion steps for a
given Sage expression?
If not, there should be one, IMHO (otherwise it's always a huge guessing
game for this sort of issues)
>
>>
>>>
>>> On Apr 21, 2017 05:10, "Dima Pasechnik" <dim...@gmail.com> wrote:
>>>
>>> On Friday, April 21, 2017 at 9:11:37 AM UTC+1, Marc Mezzarobba wrote:
>>>>
>>>> Dima Pasechnik wrote:
>>>> > but it looks as if it might be a coercion problem.
>>>> > Any ideas where to look?
>>>>
>>>> Not really, but it does look like the common parent
>>>> discovered by the coercion system is incorrect:
>>>>
>>>> sage: import numpy as np
>>>> sage: a = np.float('1.5')
>>>> sage: b = np.float32('1.5')
>>>>
>>>
>>>
>>>> sage: get_coercion_model().common_parent(b, polygen(RR))
>>>> Univariate Polynomial Ring in x over Real Field with 53 bits of
>>>> precision
>>>>
>>>> sage: RR.coerce(a)
>>>> 1.50000000000000
>>>>
>>>> sage: RR.coerce(b)
>>>> ...
>>>> TypeError: no canonical coercion from <type 'numpy.float32'> to Real
>>>> Field with 53 bits of precision
>>>>
>>>> sage: get_coercion_model().common_parent(b, RR)
>>>> <type 'numpy.float32'>
>>>>
>>>
>>> This does not look like this is the root cause of the problem.
>>> Namely, note that also
>>>
>>> sage: a128 = np.float128('1.5')
>>> sage: RR.coerce(a128)
>>> # throws the same as above TypeError, but
>>> sage: a128*x
>>> # does not print the numpy warning.
>>>
>>> what is also somewhat puzzling is
>>> that while
>>> sage: np.float32('1.5')*x
>>> # does print the numpy warning
>>>
>>> sage: x*np.float32('1.5')
>>> # just works (i.e. does not print the numpy warning)
>>>
>>> So this is a subtle combination of an apparent bug in numpy (or in
>>> clang) with
>>> some Sage coercion weirdness.
>>> Apparently numpy's floats are coerced into RDF for the purpose of
>>> dealing with polynomials, see py_scalar_to_element in
>>> structure/coerce.pyx, but apparently this only happens
>>> for
>>> x*np.float32('1.5'), and not for np.float32('1.5')*x ?
>>>
>>> Dima
>>>
>>>
>>>
>>>> --
>>>> Marc
>>>>
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