Issue 982 asks to improve the computation of the standard deviation with respect to precission. First note, that the "usual" statistics for the standard deviation (count, sum, sum of squares) is less precise than going over the sample twice: first to compute the mean and then to compute the sum of the squared differences. (The "usual" statistics has the problem small differences of large number in the "sum of squares minus sum squared" part.) However, what _can_ be improved is the way the summation is made: for our use, the values to be summed up usually differ only very little; hence summing them up in a balanced way can improve precision over linearly summing up. This is what is done in this patch series.
Klaus Aehlig (4): Add a utility function to divide lists Add a balanced version of sum Change standard deviation by balanced summing Improve sum statistics src/Ganeti/Utils.hs | 34 +++++++++++++++++++++++----------- src/Ganeti/Utils/Statistics.hs | 27 ++++++++++++--------------- 2 files changed, 35 insertions(+), 26 deletions(-) -- 2.6.0.rc2.230.g3dd15c0
