It's infeasible within our physics, but it's possible for (say) our world to be a simulation within a universe of vaster computing power, and to have a GLUT from that world interact with our simulation. I'd say that such a GLUT was extremely powerful, but (once I found out what it really was) I wouldn't call it intelligent- though I'd expect whatever process produced it (e.g. coded in all of the theorem-proof and problem-solution pairs) to be a different and more intelligent sort of process.

That is, a GLUT is the optimizer equivalent of a tortoise with the world on its back- it needs to be supported on something, and it would be highly unlikely to be tortoises all the way down.