Dear Hans,
After modifying the C++ code of this method (layer_impl.h), I was thinking on another improvement. The bottleneck in this method is the get_global_positions_vector( node_collection ) call that obtain source layer nodes positions. It takes the most execution time.
Could it be possible to add a new Python function (and its corresponding C++ implementation) with an input parameter that is these nodes positions? User can initially obtain these positions using GetPosition() PyNEST function, and afterthat use the obtained position with DumpLayerConnections().
It could be a great improvement when user call DumpLayerConnections() several times for the same source nodes.
Best,
Xavier