On 10/02/2015 16:37, Alexander Jones wrote:
Interesting. I still feel that these algorithms should be given their proper
names in a math library, because I would feel quite troubled if `Math.sum(a, b,
c) !== a + b + c`. Maybe I'm alone in this view, though. What do other
languages do?
On Friday, 2 October 2015, Waldemar Horwat <[email protected]
<mailto:[email protected]>> wrote:
On 10/02/2015 13:30, Alexander Jones wrote:
I really don't think I'd want a basic `Math.sum(a, b, c)` meaning
anything other than `a + b + c`, i.e. `(a + b) + c`. We should all just come to
terms with the fact that floating point addition is not associative.
Or is there really some simple, O(n) algorithm to do a better (more
"careful") job?
Kahan summation is simple and O(n).
There exist efficient algorithms to get the exact sum as well. See, for
example, http://www.ti3.tuhh.de/paper/rump/RuOgOi07I.pdf
Waldemar
In the cases where the algorithms produce something other than the best
practical results, giving them descriptive names would be useful. However,
compound naming can then get out of hand if you also include functions such as
average, standard deviation, etc., which include computing the sum as a
subroutine.
Waldemar
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