Re: specially ordered sets variables in Mathprog

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Binary variables are usually faster than SOS1 sets, especially when the
solver can apply some good cuts.Of course here are cases that can be
modeled with SOS1 sets and not with binary variables, but that is not what
you are dealing with..

----------------------------------------------------------------
Erwin Kalvelagen
Amsterdam Optimization Modeling Group
[email protected]
https://www.amsterdamoptimization.com <https://amsterdamoptimization.com>
----------------------------------------------------------------


On Tue, Mar 15, 2022 at 6:48 AM Tommaso Cucinotta <
[email protected]> wrote:

> Hi,
>
> I'd like to know whether Mathprog supports (or is there any plan to
> support) SOS (special ordered sets) variables, at
> least type 1.
>
> I often use mathprog and glpsol to convert MILP problems (actually, BLP
> mostly) for other solvers (CBC, CPLEX), and I'm
> seeing these other solvers support these types of variables, what makes me
> think that there might be some advantages in
> formalizing a problem this way, as perhaps the solver might be quicker in
> scanning through the possible branches etc...
> I mean, using the SOS1 native formalization, instead of equivalent
> formulations as in
>
> https://en.wikibooks.org/wiki/GLPK/Modeling_tips#Special_ordered_sets
>
> Thanks,
>
>      T.
>
> --
> Tommaso Cucinotta, Computer Engineering PhD
> Associate Professor at the Real-Time Systems Laboratory (ReTiS)
> Scuola Superiore Sant'Anna, Pisa, Italy
> http://retis.sssup.it/people/tommaso
>
>
>

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<div dir=3D"ltr"><div><br></div>Binary variables are usually faster than SO=
S1 sets, especially when the solver can apply some good cuts.Of=C2=A0course=
 here are cases that can be modeled with SOS1 sets and not with binary vari=
ables, but that is not what you are dealing with..<div><br clear=3D"all"><d=
iv><div dir=3D"ltr" class=3D"gmail_signature" data-smartmail=3D"gmail_signa=
ture"><div dir=3D"ltr"><div><div dir=3D"ltr"><div><font face=3D"verdana, sa=
ns-serif"><font color=3D"#3333FF">-----------------------------------------=
-----------------------<br>Erwin Kalvelagen<br>Amsterdam Optimization Model=
ing Group<br><a href=3D"mailto:[email protected]" target=3D"_=
blank">[email protected]</a><br><a href=3D"https://amsterdamo=
ptimization.com" target=3D"_blank">https://www.amsterdamoptimization.com</a=
><br>----------------------------------------------------------------</font=
></font></div></div></div></div></div></div><br></div></div><br><div class=
=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Mar 15, 2022=
 at 6:48 AM Tommaso Cucinotta &lt;<a href=3D"mailto:tommaso.cucinotta@santa=
nnapisa.it">[email protected]</a>&gt; wrote:<br></div><bloc=
kquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:=
1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
I&#39;d like to know whether Mathprog supports (or is there any plan to sup=
port) SOS (special ordered sets) variables, at <br>
least type 1.<br>
<br>
I often use mathprog and glpsol to convert MILP problems (actually, BLP mos=
tly) for other solvers (CBC, CPLEX), and I&#39;m <br>
seeing these other solvers support these types of variables, what makes me =
think that there might be some advantages in <br>
formalizing a problem this way, as perhaps the solver might be quicker in s=
canning through the possible branches etc... <br>
I mean, using the SOS1 native formalization, instead of equivalent formulat=
ions as in<br>
<br>
<a href=3D"https://en.wikibooks.org/wiki/GLPK/Modeling_tips#Special_ordered=
_sets" rel=3D"noreferrer" target=3D"_blank">https://en.wikibooks.org/wiki/G=
LPK/Modeling_tips#Special_ordered_sets</a><br>
<br>
Thanks,<br>
<br>
=C2=A0=C2=A0=C2=A0=C2=A0 T.<br>
<br>
-- <br>
Tommaso Cucinotta, Computer Engineering PhD<br>
Associate Professor at the Real-Time Systems Laboratory (ReTiS)<br>
Scuola Superiore Sant&#39;Anna, Pisa, Italy<br>
<a href=3D"http://retis.sssup.it/people/tommaso" rel=3D"noreferrer" target=
=3D"_blank">http://retis.sssup.it/people/tommaso</a><br>
<br>
<br>
</blockquote></div>

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