[sage-devel] Re: Changes in polynomial quotient ring are intended?

[Nils Bruin]

On Friday, December 21, 2018 at 9:10:03 AM UTC-8, Jörg-Volker wrote:
>
>
>  There is this ticket : https://trac.sagemath.org/ticket/26929 
> 
>  
> which seems to me relevant. Should I open another one anyway?
>
> That ticket already tracks and references the issue discussed here. No 
other ticket is required. 

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[sage-devel] Re: Changes in polynomial quotient ring are intended?

[Jörg-Volker]

On Thursday, December 20, 2018 at 8:38:06 PM UTC+1, Emmanuel Charpentier 
wrote:

> I agree that this seems a critical bug. Would you mind filing a ticket 
> with importance "critical" ?
>
>  There is this ticket : https://trac.sagemath.org/ticket/26929 which 
seems to me relevant. Should I open another one anyway?

Regards, Jörg.

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[sage-devel] Re: Changes in polynomial quotient ring are intended?

[Emmanuel Charpentier]

I agree that this seems a critical bug. Would you mind filing a ticket with 
importance "critical" ?

Le mercredi 19 décembre 2018 20:11:25 UTC+1, Jörg-Volker a écrit :
>
> Hi,
>
> in version 8.4 this example doesn't work anymore as it did at least until 
> version 8.2:
> varl = ['x0', 'x1', 'x2', 'x3']
> B = BooleanPolynomialRing(names = varl)
> B.inject_variables(verbose=False)
> P. = PolynomialRing(B)
> Byte. = P.quotient_ring( p^4 + p + 1 )
> X = B.gens()
> x = Byte(list(X))
> E = x^2
> print( E )
> type(Byte)
>
> Previously the outcome was
> x3*t^3 + (x1 + x3)*t^2 + x2*t + x0 + x2
>  'sage.rings.polynomial.polynomial_quotient_ring.PolynomialQuotientRing_generic_with_category'
> >
> so the result of `x^2` is also in the quotient ring. In version 8.4 I see
> x3*t^6 + x2*t^4 + x1*t^2 + x0
> 
> If this change in behaviour is intended how would I have to modify my 
> example in order to get the same results as before?
>
> Regards, Jörg.
>
>

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[sage-devel] Re: Changes in polynomial quotient ring are intended?

[John H Palmieri]

On Thursday, December 20, 2018 at 9:49:38 AM UTC-8, Nils Bruin wrote:
>
> On Wednesday, December 19, 2018 at 11:11:25 AM UTC-8, Jörg-Volker wrote:
>>
>> Hi,
>>
>> in version 8.4 this example doesn't work anymore as it did at least until 
>> version 8.2:
>> varl = ['x0', 'x1', 'x2', 'x3']
>> B = BooleanPolynomialRing(names = varl)
>> B.inject_variables(verbose=False)
>> P. = PolynomialRing(B)
>> Byte. = P.quotient_ring( p^4 + p + 1 )
>>
>
> Given that in 8.4 we now have
>
> sage: t^4+t+1 == 0
> False
>
> I think we have a fairly critical bug.
>

Notice by the way:

sage: (t^4 + t + 1).is_zero()
True
sage: (t^4 + t + 1).__nonzero__()
False
sage: t^4 + t + 1 != 0
True

So something is working, but clearly not everything.

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[sage-devel] Re: Changes in polynomial quotient ring are intended?

[Nils Bruin]

On Wednesday, December 19, 2018 at 11:11:25 AM UTC-8, Jörg-Volker wrote:
>
> Hi,
>
> in version 8.4 this example doesn't work anymore as it did at least until 
> version 8.2:
> varl = ['x0', 'x1', 'x2', 'x3']
> B = BooleanPolynomialRing(names = varl)
> B.inject_variables(verbose=False)
> P. = PolynomialRing(B)
> Byte. = P.quotient_ring( p^4 + p + 1 )
>

Given that in 8.4 we now have

sage: t^4+t+1 == 0
False

I think we have a fairly critical bug.

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