Use Kahan summation for sum accumulator #628
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Signed-off-by: Ahmed Hassan <[email protected]>
yeya24
approved these changes
Sep 24, 2025
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Every time an arithmetic operation is done on two float64 variables the result is calculated at high precision then rounded to the nearest possible float representation. This error accumulates when summing a large set of series, and can become significant.
In Prometheus, we use Kahan summation to compensate for this error when aggregating SUM operation. We do not do the same currently in Thanos.
Kahan Summation https://en.wikipedia.org/wiki/Kahan_summation_algorithm