[sage-support] Bug in symbolic integration?

2021-06-15 Thread 'Hendrik Suess' via sage-support
The following two functions f(u)=-u/2+min_symbolic(0,u) + min_symbolic(u,2*u) and g(u)=-u/2+min_symbolic(u, 3*u) are mathematically equivalent, but the following symbolic integrals give different results. F(x)=integral(f(u)*u*exp(x*u),u,-1,1) FF(y)=F(y) G(x)=integral(g(u)*u*exp(x*u),u,-1,

[sage-support] Symbolic integration: change of behaviour between versions 8.3 and 9.3

2021-06-15 Thread 'Hendrik Suess' via sage-support
The following Sage code var('u') integrate(-1/8*(u - 2*min_symbolic(-1/2*u - 1/2, 1/2*u - 1/2) - 1)^2 + 1/2*(min_symbolic(0, u) + 1)^2,u,-1,1) produces 1/2 as a (correct) result with SageMath 8.3 (running with Software Environment Ubuntu 18.04 @ 2018-08-27 in CoCalc). With SageMath 9.3 (ru

Re: [sage-support] Matricial conversion of a system of inequations.

2021-06-15 Thread cyrille.piate...@univ-orleans.fr
Yes I am aware of it and also use it. What I need is a step by step Fourier Motzkin decomposition. It's for teaching reasons. I want also be able to draw the projections implied by it from 3D to 2D and 1D. Then I plot it in Asymptote (because on html it has latex label even in 3D, which is not t

Re: [sage-support] Matricial conversion of a system of inequations.

2021-06-15 Thread Dima Pasechnik
Just checking - are you aware of Sage's functionality to deal with constructing of polyhedra by linear inequalities and equations? It seems you are trying to do the same, but in a rather inefficient way. On Tue, 15 Jun 2021, 09:58 cyrille.piate...@univ-orleans.fr, < cyrille.piate...@univ-orleans.f

[sage-support] Matricial conversion of a system of inequations.

2021-06-15 Thread cyrille.piate...@univ-orleans.fr
The following code write a system of inequations x = vector(SR, SR.var('x_', 7)) A = random_matrix(SR,7,7) b = random_vector(SR,7) o = zero_vector(SR,7) Z=[SR(A[i]*x-b[i])<=SR(o[i]) for i in range(A.nrows())] SR(x[1]).variables()[0] Sol=[solve(SR(Z[i]),SR(x[2]).variables()[0])[1] for i in r