ok. I made a pull request for the linear programing solver and I did not add the inequalities functions in the commit for now. The pull request number is #21673 waiting for your aproval/corrections. thank you!
On Sunday, 20 June 2021 at 22:33:16 UTC+3 Oscar wrote: > Okay, that code looks good. It will also need docs and tests. > > I suggest first trying to add the smallest part of this to sympy. Then > other parts can be added one step at a time. > > The question is what is the smallest part that is useful on its own. > Is that the simplex function? > > If you open a pull request to add that to sympy then you can get some > feedback on it and make further changes until it is ready. Once that > part is merged you will have a better idea how to prepare the other > parts for inclusion into sympy. > > Another question is performance. I expect that in practice the most > important part of the performance of this method is being able to > handle large sparse systems of mostly unrelated inequalities so being > able to separate a system using sparse techniques to reduce the size > of the problem will make the method much faster in common usage. > > Oscar > > On Sat, 19 Jun 2021 at 21:31, אוריאל מליחי <orielm...@gmail.com> > wrote: > > > > Yes, my code is viewable in here- > > > https://github.com/orielmalihi/Final-Project/blob/main/my%20functions/inequalities%20functions.py > > > > On Friday, 18 June 2021 at 00:09:11 UTC+3 Oscar wrote: > >> > >> That's great. I suggest not trying to add everything at once. Probably > some changes will need to be made and there are other steps like tests and > so on that would need to be added if there aren't already tests in the > right format. > >> > >> Is your code publicly viewable already? For example if you put it in a > github repo/gist then you can send a link here. > >> > >> Oscar > >> > >> On Thu, 17 Jun 2021 at 20:17, אוריאל מליחי <orielm...@gmail.com> > wrote: > >>> > >>> Hello everyone! > >>> > >>> I finally completed implementing these functions. > >>> > >>> Quick reminder: > >>> The main function is called is_implied_by and it gets a set of linear > inequalities and a target linear inequality and return whether the target > is implied by the set or not. > >>> > >>> Two other functions are find_values_interval and > simplify_linear_inequalities. > >>> > >>> find_values_interval gets a set of linear inequalities and a target > expression (expr) and returns an interval of [min possible value for expr, > max possible value for expr]. > >>> > >>> simplify_linear_inequalities gets a set of linear inequalities and > returns a simplified set (redundant inequalities are removed). > >>> > >>> Now I would like to know what are the next steps for me to do in order > to get my implementation into sympy. This is my first time contributing so > detailed explanation would be really helpful. > >>> > >>> > >>> > >>> On Thursday, 18 February 2021 at 18:28:38 UTC+2 oscar.gu...@gmail.com > wrote: > >>>> > >>>> Den tors 18 feb. 2021 kl 14:36 skrev Oscar Benjamin < > oscar.j....@gmail.com>: > >>>>> > >>>>> On Thu, 18 Feb 2021 at 11:32, Oscar Gustafsson > >>>>> <oscar.gu...@gmail.com> wrote: > >>>>> > > >>>>> > After currently using Mathematica for similar things, I would just > like to encourage you to provide some nice method to simplify constraints > of piecewise functions using your simplifier, including additional > constraints on the range of variables (as SymPy doesn't have a way to put > ranges on variables). That doesn't really exist in Mathematica > (Assuming[..., Simplify[piecewise]) doesn't always seems to simplify as far > as possible). > >>>>> > > >>>>> > Something like > >>>>> > simplify_piecewise_range(piecewisefunction, common_constraints) > >>>>> > That adds the common_constraints to each region constraint and > applies your method. (Possibly, optionally, removing the common_constraints > from the final regions if feasible.) > >>>>> > >>>>> I imagined that this would be something that the new assumptions > could > >>>>> handle in refine. Something like: > >>>>> > >>>>> p = Piecewise((x, x < 1), (x**2, True)) > >>>>> p = refine(p, abs(x) < 1) > >>>>> > >>>>> The idea would then be that e.g. when you have Integral(f, (x, a, b)) > >>>>> then the integration routine can do > >>>>> > >>>>> f = refine(f, (a < x) & (x < b)) > >>>> > >>>> Yes, a different assumption system will also do the trick. But until > that is in place, this would be a useful short-cut for a specific use case. > >>>> > >>>> > >>>>> > There is an old PR which may be useful to revive in relation to > this: https://github.com/sympy/sympy/pull/17443 although sort of > independent. > >>>>> > > >>>>> > It will also be useful to have a function that can replace Min/Max > expressions with linear inequalities (and possibly back again). Right now > there is some logic to convert from linear inequalites to Min/Max, but not > back. As far as I recall. (There may be a PR doing the Min/Max to linear as > well, but not really sure.) > >>>>> > >>>>> Is this what you mean? > >>>>> > >>>>> In [1]: Min(x, y).rewrite(Piecewise) > >>>>> Out[1]: > >>>>> ⎧x for x ≤ y > >>>>> ⎨ > >>>>> ⎩y otherwise > >>>>> > >>>>> Perhaps there could be a rewrite(Max) for Piecewise. > >>>>> > >>>> I seem to recall that I did something that rewrote/simplified, > probably as part of the pattern based logic simplification, > >>>> And(x <= y, x <= z) > >>>> to > >>>> x <= Min(y, z) > >>>> > >>>> At some later stage I realized it was sometimes a bad idea (as the > logic simplification sometimes worked better without the Min/Max, do not > recall exactly) and I sort of regretted introducing that rewrite, but > cannot recall if the reverse operation was ever introduced. Piecewise may > work though, but I believe that for the linear inequality simplifier it may > be better to rewrite x <= Min(y, z) back to And(x <= y, x <= z) . > >>>> > >>>> BR Oscar > >>>> > >>> -- > >>> You received this message because you are subscribed to the Google > Groups "sympy" group. > >>> To unsubscribe from this group and stop receiving emails from it, send > an email to sympy+un...@googlegroups.com. > >>> > >>> To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/07668755-217b-4487-805d-1faefd70191bn%40googlegroups.com > . > > > > -- > > You received this message because you are subscribed to the Google > Groups "sympy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sympy+un...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/6ae5a93d-5976-479d-ad87-017a0c82b603n%40googlegroups.com > . > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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