[Couenne] Binary Variables

[Pietro Belotti]

See also ticket #40 https://projects.coin-or.org/Couenne/ticket/40



On Fri, Aug 24, 2018 at 5:27 PM Murilo Souza <muriloasouza at hotmail.com>
wrote:

> Hello, i'm using Couenne in Atom/Juno, through Julia language, to solve
> some MINLP problems.
>
> But i have an issue with this following problem (it's a random problem i
> just wrote to test the Couenne solver in Atom):
>
> ## Solve test problem
>  #
>  #  min   100 * (x5 - (0.5 + x4) ^ 2) ^ 2 + (1 - x4) ^ 2
>  #  s.t.  x4*x3 + x5*x1 <= 20
>  #        5*x1 - 2*x5 + 3*x3 <= 17
>  #        x4, x5 binary
>  #        0 <= x1 <= 3
>  #        0 <= x2 <= 5
>  #        0 <= x3 <= 10
>  ##
>
> The problem is being solved to optimal point, but my binary variable x4 is
> not assuming a binary value. Here is the solution i found:
>
> x1 = 1
> x2 = 2.5
> x3 = 2
> x4 = 0.50124...
> x5 = 1
>
> Why is this happening? How can i fix this?
>
> Thanks in advance,
> Murilo Souza
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