

Log-probabilities, semirings and floating point numbers - Watermelon
http://blog.smola.org/post/987977550/log-probabilities-semirings-and-floating-point-numbers

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jgrahamc
As the author says this is pretty common in machine learning circles. I used
the same trick in POPFile for text classification because you end up dealing
with tiny probabilities, but manageable negative log probabilities. And
clearly division is just subtraction, just as multiplication becomes addition.

What amused me at the time was that this is how people used to do
multiplication with a slide rule or log table. Funny how old ideas come back.

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hga
Heh, I'm just old enough to have learned the log table method in high school
Algebra II; that was right after scientific calculators hit $90 in 2010
dollars (<http://en.wikipedia.org/wiki/TI-30> at $25 then) but of course the
books hadn't caught up yet. And the trick is indeed very useful.

