Kahan summation: Difference between revisions
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(Example implementation in R, with comparison to the standard sum() implementation) |
m (added the a+b+c code) |
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> # make R display more digits in the result |
> # make R display more digits in the result |
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> options(digits=10) |
> options(digits=10) |
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> a <- 10000.0 |
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> b <- 3.14159 |
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> c <- 2.71828 |
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> a + b + c |
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[1] 10005.85987 |
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> # no problem there |
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> input <- c(10000.0, 3.14159, 2.71828) |
> input <- c(10000.0, 3.14159, 2.71828) |
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> kahansum(input) |
> kahansum(input) |
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[1] 10005.85987 |
[1] 10005.85987 |
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> # compare with the standard sum() function |
> # for completeness, let's compare with the standard sum() function |
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> sum(input) |
> sum(input) |
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[1] 10005.85987 |
[1] 10005.85987 |
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> # seems like R does the "right thing" |
> # seems like R does the "right thing" |
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> # bonus: |
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> # let's use the Dr. Dobbs example (http://www.drdobbs.com/floating-point-summation/184403224) |
> # let's use the Dr. Dobbs example (http://www.drdobbs.com/floating-point-summation/184403224) |
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> input <- c(1.0, 1.0e10, -1.0e10) |
> input <- c(1.0, 1.0e10, -1.0e10) |
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