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Implement exact summation (fsum)? #152

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Fil opened this issue Jun 15, 2020 · 1 comment · Fixed by #154
Closed
4 tasks done

Implement exact summation (fsum)? #152

Fil opened this issue Jun 15, 2020 · 1 comment · Fixed by #154
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Fil commented Jun 15, 2020 •
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Discussed with Kahan summation (#33, #149), fsum is a bit slower but provably "exact" and would be the preferred "exact summation" algorithm for d3-array.

I've implemented it in https://observablehq.com/d/723090bd2ef54f5f ; it does not return a sum but an object that can be used to continue the sum by adding more terms.

  • speed test (about 2x slower than d3.sum which is not that bad)
  • a valueof accessor
  • check if this implementation is useful in d3-geo.
  • document
@Fil Fil self-assigned this Jun 15, 2020
This was referenced Jun 15, 2020
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Fil commented Jun 17, 2020

Good news: replacing d3-geo/adder with fsum can help solve https://observablehq.com/@fil/small-circle-test by enhancing the precision of the sums.

Fil added a commit that referenced this issue Jun 23, 2020
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d3.fsum
313e4d6 
exact summation of IEEE 754 numbers
fixes #152 (see also #33)
@Fil Fil mentioned this issue Jun 23, 2020
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@Fil Fil closed this as completed in #154 Jul 30, 2020
Fil added a commit that referenced this issue Jul 30, 2020
@Fil @mbostock
d3.fsum (#154)
73ca8a7 
* d3.fsum / d3.Adder
exact summation of IEEE 754 numbers
fixes #152 (see also #33)

Co-authored-by: Mike Bostock <mbostock@gmail.com>
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d3.fsum d3/d3-array
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