The answer you show suggests that you are using library(clpq)
and not library(clpr)
. In the original implementation of this library in SICStus Prolog, I get:
| ?- {Ta >= 0,
Ta + 2 =< Tb,
Ta + 2 =< Tc,
Tb + 3 =< Td,
Tc + 5 =< Tf,
Td + 4 =< Tf},
minimize(Tf).
Ta = 0,
Tb = 2,
Td = 5,
Tf = 9,
{Tc=<4},
{Tc>=2} ?
yes
So this seems to be a bug in SWI. Probably some variables have not been projected away.