> I don't know what you are working on but if you use fractions for what you are > doing it would be interesting to hear about how you use them and your results. > Because fractions are kept as an integer numerator and an integer denominator, > they probably take up more memory than floats but less than ScaledDecimals. > And > because both the numerator and denominator can be large integers, fractions > can > be very precise. But because they are implemented in both software and > hardware, then can be slow. However, many numerical functions seem to have > fractions or divisions built into them. If fractions are used and the > divisions > not preformed until they absolutely have to be, then use of fractions could be > faster than expected and may be faster than ScaledDecimals or floats. I have > no > proof of this but if you do anything in this area, I would love to hear about > it.
I think all this is premature optimization for me :) as I'm only building an early prototype (I'm doing a start of Dempster Shafer Theory [1] implementation (actually Transferable Belief Model)... and it's won't reach a big size for a while. It allows to have an imprecise, incomplete even uncertain value for a proposition (sort of multi-valued attribute with confidence...). I use it to get expert opinion on values, it's a known technique for different captor data fusion, but in my case, it doesn't demand too much performance as the combination is not that important (compared to sensor data fusion) ;) Talking about that, that make me remember I needed a method subsets (for Set) and didn't found one. So I implementented one which will be cool to discuss here maybe (instead of something iterative, I've hacked something with binary masks, so it's 2 methods - 2 methods that took me two days but that's the fun of Smalltalk ! :) Cédrick [1] http://en.wikipedia.org/wiki/Dempster-Shafer_theory
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