Switching of RRGraphView's Routing Resource Graph

[ethanroj23]

One of the use cases of adding an API to VPR for the routing resource graph was to be able to alter the way the RRGraph was represented and still use it throughout VPR.

I have been working on folding the RRGraph to reduce the size it takes up in memory, especially when it grows very large. I have implemented an abstract class so that the RRGraphView object can make use of several different RRGraph classes. RRGraphView has a pointer to an interface class (RRGraphViewInterface ) which several different types of RRGraph classes inherit from. Whenever one wants to change the RRGraph in use, they simply change where the RRGraphViewInterface pointer is pointing.

This method has allowed me to dynamically select which RRGraph to use, but it has come at a cost. VPR runs more slowly after adding in this interface class and methodology. I believe this may be due to the vtable lookups which occur for every function call to the RRGraph derived classes. The lookup should be minimal, but because there are so many calls to the RRGraph functions, I think this is where the issue is.

Does anyone know of a better way to be doing this? The only way I have thought of so far involves inheritance, but I am hoping there's a better way. Essentially, I just need to be able to change which class the RRGraphView uses to call the RRGraph access functions.

[tangxifan]

@ethanroj23 Would you mind providing some code examples? I can better understand the scenario.

[ethanroj23]

Sure thing. Here are some of the files in question. RRGraphViewInterface RRGraphView

Specifically, the RRGraphView has a pointer to the interface class that it uses to access functions. RRGraphViewInterface* primary_rr_graph_;

I think this abstract class pointer may be preventing inlining the function calls that RRGraphView makes.