Finding appropriate bound sets of variables is the most important task of functional decomposition. When solving some problems the bound sets need to be large, for instance in decomposition to symmetric subfunctions realized in MOPS arrays for submicron technologies, or when no good small bound sets exist. In such cases the creation of the incompatibility graph, that is necessary to evaluate good variable partitionings, becomes very inefficient. Therefore an algorithm is proposed here, that can speed up this process by orders of magnitude without sacrifying the quality of the decomposition, because the same graph coloring algorithms (exact or approximate) is still applied to the created graph.