[sage-support] Re: groebner basis algorithm: intended way of calling (out of other method)
On 2019-02-08, Daniel Krenn wrote: > Which algorithm does not return a *reduced* Gröbner basis? Singular has some options that determine whether or not a reduced GB is returned. I simply don't know (and have at the moment no time to look at the code) whether this option is used. Also, IIRC, there is some toy implementation of Buchberger's algorithm (which is mainly for teaching, not for production), and I am not sure if it returns a reduced GB. In any case, if the documentation says it returns a *reduced* GB, then we certainly have a bug. Either a bug in the documentation (if in fact the returned GB is not always reduced) or in caching (if it *is* the reduced GB and isn't cached). Best regards, Simon -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
Re: [sage-support] Re: groebner basis algorithm: intended way of calling (out of other method)
On 2019-02-08 10:33, Simon King wrote: > On 2019-02-08, Daniel Krenn wrote: >> Let I be an ideal. Then I might want to compute something involving >> Groebner basis, e.g. computing I.variety(). >> Now suppose one wants to select a particular algorithm for the >> computation of the Groebner basis. Then (due to caching) I use something >> along the lines of >> >> GB = I.groebner_basis(algorithm='libsingular:slimgb') >> I.groebner_basis.set_cache(GB) >> I.variety() >> >> Is this the intended way of doing so? > > I guess not. I would expect that I.groebner_basis uses caching > regardless of the used algorithm. Are you sure that this is not the > case? Not the case; I've carefully checked the code. > Or do you say that I.groebner_basis sets a cache item for each possible > value of "algorithm" individually? That would probably be a bug (i.e., > please open a ticket). Yes, this is what I am saying. And indeed my implied question is, whether this is a bug. > Why "probably"? *Reduced* Gröbner bases are unique, hence, they should > be cached independently of the algorithm used to compute them. But some > algorithms would only call *some* Gröbner basis, no *the* reduced > Gröbner basis. So, in these cases it makes sense to not automatically > cache the value. And indeed again, this is why I didn't open a ticket up to now. On the contrary, the one-line description says "Return the reduced Groebner basis of this ideal" Therefore, the intended result is unique and therefore, we have a bug as above). Which algorithm does not return a *reduced* Gröbner basis? Best, Daniel -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: groebner basis algorithm: intended way of calling (out of other method)
Hi Daniel, On 2019-02-08, Daniel Krenn wrote: > Let I be an ideal. Then I might want to compute something involving > Groebner basis, e.g. computing I.variety(). > Now suppose one wants to select a particular algorithm for the > computation of the Groebner basis. Then (due to caching) I use something > along the lines of > > GB = I.groebner_basis(algorithm='libsingular:slimgb') > I.groebner_basis.set_cache(GB) > I.variety() > > Is this the intended way of doing so? I guess not. I would expect that I.groebner_basis uses caching regardless of the used algorithm. Are you sure that this is not the case? Or do you say that I.groebner_basis sets a cache item for each possible value of "algorithm" individually? That would probably be a bug (i.e., please open a ticket). Why "probably"? *Reduced* Gröbner bases are unique, hence, they should be cached independently of the algorithm used to compute them. But some algorithms would only call *some* Gröbner basis, no *the* reduced Gröbner basis. So, in these cases it makes sense to not automatically cache the value. Best regards, Simon -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] groebner basis algorithm: intended way of calling (out of other method)
Let I be an ideal. Then I might want to compute something involving Groebner basis, e.g. computing I.variety(). Now suppose one wants to select a particular algorithm for the computation of the Groebner basis. Then (due to caching) I use something along the lines of GB = I.groebner_basis(algorithm='libsingular:slimgb') I.groebner_basis.set_cache(GB) I.variety() Is this the intended way of doing so? (It somehow feels wrong that one needs quite some background on the implementation and technical understanding (caching in SageMath) to understand the behavior.) Details: A method using a Groebner basis calls self.groebner_basis(), i.e. uses default arguments or whatever is cached. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
