Issue #10298 has been updated by Nobuyoshi N…
It doesn’t improve the performance as Array.float_sum, though.
Feature #10298: Array#float_sum (like math.fsum of Python)
- Author: Takeshi Nishimatsu
- Status: Feedback
- Priority: Low
- Assignee:
- Category: math
- Target version:
Here, I propose Array#float_sum in array.c (or math.c).
Array#float_sum returns an accurate total summation of Float
elements in an array using the Kahan summation algorithm
Kahan summation algorithm - Wikipedia .
This algorithm can significantly reduce the numerical
error in the total obtained by adding a sequence of
finite precision floating point numbers, compared to the
obvious approach. Python already have math.fsum
9.2. math — Mathematical functions — Python 2.7.18 documentation .
[0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1].float_sum #=> 1.0
[].float_sum #=> 0.0
Array.new( 10, 0.1).float_sum #=> 1.0
Array.new(100, 0.1).float_sum #=> 10.0
# cf.
Array.new( 10, 0.1).reduce(:+) #=> 0.9999999999999999
Array.new(100, 0.1).reduce(:+) #=> 9.99999999999998
The name of method can be fsum, sum_float, etc., though
I propose float_sum.
This Array#float_sum is inspired by Feature #9834
Float#{next_float,prev_float}.
—Files--------------------------------
array.float_sum.patch (1.32 KB)