Slow performance compared to C++, ideas?

[estew]

Two quick notes:

a) Profile first the optimise.


b) This probably wouldn't make 4x difference but in the C++ code 
you're passing most objects around by ref. In the D version 
you're passing structs by value.

They are only small but there's a tight loop of recursion to 
consider...

That said, I don't know the details of D optimisation all that 
well and it may be a non-issue in release builds.

Stewart