Here we go. Thanks for taking care of it, Matthias! Michael Jung schrieb am Montag, 5. April 2021 um 00:29:07 UTC+2:
> Meaning, I will post it here. > > Michael Jung schrieb am Montag, 5. April 2021 um 00:28:24 UTC+2: > >> Alright, thanks. For now then, I'll post my proposal the upcoming days. >> Is markdown format fine? >> Matthias Koeppe schrieb am Sonntag, 4. April 2021 um 21:59:53 UTC+2: >> >>> I think you will need to ask for a legacy Trac account. Editing the wiki >>> with a GitHub account is not supported. >>> https://trac.sagemath.org/wiki/WikiStart#legacy-account-request >>> >>> On Sunday, April 4, 2021 at 12:06:50 PM UTC-7 Michael Jung wrote: >>> >>>> Is there a way I can get access though? There is a bit more worth to >>>> add: >>>> - https://trac.sagemath.org/ticket/18416 >>>> - https://trac.sagemath.org/ticket/8972 >>>> >>>> Especially the first ticket should be mentioned because it changes the >>>> behavior of power series rings. >>>> Matthias Koeppe schrieb am Sonntag, 4. April 2021 um 18:49:31 UTC+2: >>>> >>>>> Just post the text here that you want added and I can add it. >>>>> >>>>> On Sunday, April 4, 2021 at 9:29:08 AM UTC-7 Michael Jung wrote: >>>>> >>>>>> >>>>>> It might also worth to mention that the Pfaffian of a matrix can now >>>>>> be computed with a much way faster algorithm: >>>>>> https://trac.sagemath.org/ticket/30681. >>>>>> >>>>>> I would add an example to the Release tour but I don't know how or I >>>>>> don't have access... >>>>>> Samuel Lelievre schrieb am Montag, 22. März 2021 um 03:29:41 UTC+1: >>>>>> >>>>>>> I observed the error when you pointed it out, but it is now >>>>>>> fixed for me too. Temporary MathJax glitch? --Samuel >>>>>>> >>>>>> -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/e5dcbfe8-4759-4ffd-924a-7a520f173f7an%40googlegroups.com.
# Algebra ## Power Series Ring The method `set_default_prec` is now deprecated since it led to unwanted behavior (see #18416 for details). If another default precision is needed, a new power series ring must be created: ```python sage: R.<x> = PowerSeriesRing(QQ, default_prec=10) sage: sin(x) x - 1/6*x^3 + 1/120*x^5 - 1/5040*x^7 + 1/362880*x^9 + O(x^10) sage: R.<x> = PowerSeriesRing(QQ, default_prec=15) sage: sin(x) x - 1/6*x^3 + 1/120*x^5 - 1/5040*x^7 + 1/362880*x^9 - 1/39916800*x^11 + 1/6227020800*x^13 + O(x^15) ``` That change does not affect the behavior of its ring elements. Code that relies on this method needs to be updated. * Inversion of power series ring elements does now provide the correct parent: #8972 ## Bär-Faddeev-LeVerrier algorithm for Pfaffian According to https://arxiv.org/abs/2008.04247, the Pfaffian of skew-symmetric matrices over commutative torsion-free rings can be computed with a Faddeev-LeVerrier-like algorithm. This algorithm is now implemented under the weaker assumption of the base ring being a Q-algebra (#30681). It leads to a significant increase of computational speed in comparison to the definition involving perfect matchings, which has been the only algorithm available in Sage so far. With the definition: ```python sage: A = matrix([(0, 0, 1, 0, -1, -2, -1, 0, 2, 1), (0, 0, 1, -3/2, 0, -1, 1/2, 3, 3/2, -1/2), (-1, -1, 0, 2, 0, 5/2, 1, 0, -2, 1), (0, 3/2, -2, 0, 5/2, -1, 2, 0, -1, -3/2), (1, 0, 0, -5/2, 0, 0, -1, 1/2, 1, -1), (2, 1, -5/2, 1, 0, 0, 2, 1, 2, 1), (1, -1/2, -1, -2, 1, -2, 0, 0, -3, -1), (0, -3, 0, 0, -1/2, -1, 0, 0, 1/2, 1/2), (-2, -3/2, 2, 1, -1, -2, 3, -1/2, 0, 1), (-1, 1/2, -1, 3/2, 1, -1, 1, -1/2, -1, 0)]) sage: %%time ....: A.pfaffian(algorithm='definition') CPU times: user 18.7 ms, sys: 0 ns, total: 18.7 ms Wall time: 18.6 ms 817/16 ``` With Bär-Faddeev-LeVerrier: ```python sage: A = matrix([(0, 0, 1, 0, -1, -2, -1, 0, 2, 1), (0, 0, 1, -3/2, 0, -1, 1/2, 3, 3/2, -1/2), (-1, -1, 0, 2, 0, 5/2, 1, 0, -2, 1), (0, 3/2, -2, 0, 5/2, -1, 2, 0, -1, -3/2), (1, 0, 0, -5/2, 0, 0, -1, 1/2, 1, -1), (2, 1, -5/2, 1, 0, 0, 2, 1, 2, 1), (1, -1/2, -1, -2, 1, -2, 0, 0, -3, -1), (0, -3, 0, 0, -1/2, -1, 0, 0, 1/2, 1/2), (-2, -3/2, 2, 1, -1, -2, 3, -1/2, 0, 1), (-1, 1/2, -1, 3/2, 1, -1, 1, -1/2, -1, 0)]) sage: %%time ....: A.pfaffian(algorithm='bfl') CPU times: user 554 µs, sys: 41 µs, total: 595 µs Wall time: 599 µs 817/16 ```
