[Maxima] strange decay of performance of Maxima
O.Kullmann at swansea.ac.uk
Wed Feb 18 13:04:29 CST 2009
I'm experiencing strange bad performance, which perhaps
relates to bad memory management (using Maxima 5.17.1 and
I have a function f(n) (say; I don't think that the precise
details matter here), which computes a list of length
proportional to n.
The main function is F(n), which just computes the concatenation
of f(1), ..., f(n) (there are some complications, but I don't think
In order to speed-up the computation, f(n) is actually f[n],
so it memoises (the point here is that F(n) needs to be investigated,
and then typically a new computation F(n') is launched, where n' is
somewhat smaller or somewhat bigger).
Now here are the running times:
Evaluation took 116846.9500 seconds (185530.3700 elapsed)
Evaluation took 22433.8660 seconds (22988.8430 elapsed)
Evaluation took 34525.6380 seconds (34642.6760 elapsed)
Evaluation took 52942.4810 seconds (53078.5270 elapsed)
Evaluation took 58397.8730 seconds (59343.3410 elapsed)
Evaluation took 73483.6930 seconds (73506.2950 elapsed)
Already the computation at 129 looks a bit lame, but so well, until
line 130 it seems basically alright. But the computation at 131 should
have taken definitely much less than the computation at 130, and the
computation at line 132 should have taken not more than the computation
at 131. So something's going wrong here.
Memory usage is about 1GB.
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