General performance tips

[albert-j via Digitalmars-d-learn]

> 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.