On Sat, 02 May 2020 18:50:30 GMT, Russel Winder wrote:

I am surprised D is slower than Python, but I am not surprised that Python is not slow. At least in this case, most of the work is likely in native code in both cases.

Yes, most of the Python work is really done by C code.
Also, the model makes heavy use of sets which are native to Python whereas for D I have to simulate them using AAs.