Function GraphOptions.allowVertexFiltering
This is a specialized option that is only needed by clients want to work with the graphs for multiple layers at the same time (e.g., in order to check whether the same edge is present in two different graphs). [Note that if you need to do this, usually it is easier just to build a single graph with suitable edge labels.]
bool allowVertexFiltering() const;
When there are a large number of layers, then by default S2Builder builds a minimal subgraph for each layer containing only the vertices needed by the edges in that layer. This ensures that layer types that iterate over the vertices run in time proportional to the size of that layer rather than the size of all layers combined. (For example, if there are a million layers with one edge each, then each layer would be passed a graph with 2 vertices rather than 2 million vertices.)
If this option is set to false, this optimization is disabled. Instead the graph passed to this layer will contain the full set of vertices. (This is not recommended when the number of layers could be large.)
DEFAULT
true