scott wrote:
>>> That was using 1 core of an Intel E8500 @ 3.16 GHz.
>>
>> OK. My hardware is considerably less powerful.
>>
>> Is that RK4 with a single step, or with adaptive step subdivision?
> 
> Just one complete integration step of plain RK4.  I didn't do any 
> checking to see if sub-steps are needed or not.

That's probably why my version is slower then.

It computes one step forward. It then recomputes that step as two 
half-steps. Finally, it computes the difference between the two answers. 
If the difference is too large, the first result is thrown away, and 
further subdivision is done to check the second result is OK. (There is 
a maxmimum number of subdivisions though - or rather, a minimum step size.)

I can try turning that off to see what speed I get - but I'm still 
running on different hardware to you, so it's probably not very meaningful.

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