Figure 13: The Optimize Menu (PC)
This menu is the most important feature of Graph'O->Mat. It helps you to place your graph in different manners. You can find more information on these optimization algorithms on page 
in section 3.
The first option named 'Standard' looks for minimal edge-length without moving the vertices. The 'Circle' option places all vertices in a circle and applies the 'Standard' algorithm. The rest of these options are varieties of the 'Circle' option. 'Centered Circle' places the vertex with the most connection in the middle of the circle. 'Double Circle' places the vertices in two shifted circles with different diameters. and finally 'Centered 2-Circle' does the same thing with a vertex in the middle.
You cannot just say that one of these options gives you the best result. It really depends on the kind of graph you have to place. Best thing is to try the different algorithms and to sometimes repeatedly choose the 'Standard' option to get best results.