Am Freitag, 6. Mai 2005 16:58 schrieb Greg Buchholz: > Daniel Fischer wrote: > > The problem is that a prime crept in in Josef's code, > > so to calculate the positions and velocities, the updated versions of the > > planets are used, it should be > > Ah, yes, thanks for the correction. > > > Besides, offset_momentum does not use the parameter n at all and I think > > that all the indexing in the computation of the potential energy is > > rather inefficient. > > I wasn't too worried about the energy function, since it only gets > called twice, whereas the "advance" get called potentially millions of
Of course, and for only five bodies... > times (and must be the source of the space leak). You can see one > profile I ran (for n=1000 instead of 1000000) at... I did profiling for n = 20000 and n = 100000, if I read the profiles correctly, Josef's code reduces memory usage by a factor of 2 resp. 3, which ain't bad. Maybe one could reduce space usage further by not creating the list of iterations but instead make it a tail recursive function? I'll try. > > http://sleepingsquirrel.org/nbody/nbody.prof > > Thanks, > > Greg Buchholz One question: the energy of the system should be constant - that little physics I know. What I don't know is whether the change in energy in this simulation is within usual, reasonable bounds or not. If not, is it due to a too long time interval or should one use a more sophisticated algorithm? Cheers, Daniel _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
