On Tue, Jun 07, 2016 at 17:06:16 +0300, Sergey Fedorov wrote: > On 07/06/16 02:40, Emilio G. Cota wrote: > > On Fri, Jun 03, 2016 at 20:46:07 +0300, Sergey Fedorov wrote: > >> Maybe something like > >> https://en.wikipedia.org/wiki/Kahan_summation_algorithm could help? > > That algorithm is overkill for what we're doing. Pairwise summation > > should suffice: > > > > diff --git a/util/qdist.c b/util/qdist.c > > index 3343640..909bd2b 100644 > > --- a/util/qdist.c > > +++ b/util/qdist.c > > @@ -367,20 +367,34 @@ unsigned long qdist_sample_count(const struct qdist > > *dist) > > return count; > > } > > > > +static double qdist_pairwise_avg(const struct qdist *dist, size_t index, > > + size_t n, unsigned long count) > > +{ > > + if (n <= 2) { > > We would like to amortize the overhead of the recursion by making the > cut-off sufficiently large.
Yes, this was just for showing what it looked like. We can use 128 here like JuliaLang does: https://github.com/JuliaLang/julia/blob/d98f2c0dcd/base/arraymath.jl#L366 (snip) > Otherwise looks good. Thanks! Emilio
