Without seeing the source there is nothing we can do. Usually performant d-code looks quite diffrent from java code. For example to avoid the gc :)
Well it is actually ODE solver from Numerical recipes (originally in C++) that I am trying to do in D. Code translation seems very straightforward. Maybe there's someone around who has done that already? There's not much object creation going on there, mostly loops over arrays, so I assume GC is not an issue.
