Implementation details and current issues

This page is about implementation details. It isn’t necessary to understand general principles, but it helps before reading the code.

STDCMEdgeBuilder

This refers to this class in the project.

This class is used to make it easier to create instances of STDCMEdge, the graph edges. These contain many attributes, most of which can be determined from the context (e.g. the previous node). The STDCMEdgeBuilder class makes some parameters optional and automatically computes others.

Once instantiated and parameterized, an STDCMEdgeBuilder has two methods:

• makeAllEdges(): Collection<STDCMEdge> can be used to create all the possible edges in the given context for a given route. If there are several “openings” between occupancy blocks, one edge is instantiated for each opening. Every conflict, their avoidance, and their related attributes are handled here.

• findEdgeSameNextOccupancy(double timeNextOccupancy): STDCMEdge?: This method is used to get the specific edges that uses a certain opening (when it exists), identified here with the time of the next occupancy block. It is called whenever a new edge must be re-created to replace an old one. It calls the previous method.

Past path data

During the exploration, we simulate each block on its own, ignoring where the train comes from. This is done to improve caching, and because past path data is currently difficult to fetch.

This has two issues:

• We need to consider that speed limits apply until the train head leaves the speed limit range. This is technically wrong, it should be dismissed when the train tail leaves it.
• During the search, we don’t know the slopes on the tracks still covered by the train. This can lead to accelerations that are too optimistic, and in rare cases to post-processing errors.

There’s an open issue, but we don’t have a clear plan nor the time to work on it (yet).