Hi, On Thu, Dec 17, 2020 at 4:50 PM Dominique Devienne via Boost-users < boost-users@lists.boost.org> wrote:
> I'm already using the accumulator below to keep track of request > processing times of a server. > > using ProcAcc = acc::accumulator_set< > double, acc::stats< > acc::tag::min, > acc::tag::max, > acc::tag::mean, > acc::tag::median, > acc::tag::sum > > > >; > > But now I'm interested in also extracting the P90 and P99 values, > to get insight in how much of an outlier the max could be. > > AFAIK, the median is the P50, but it's not readily obvious to me what tag > to use for the P90 or P(N) in general. Could someone help please? Thanks, > --DD > > PS: Does accumulator allow to keep the top(N) values as well? How? > The Boost.Accumulators documentation provides examples on how to compute quantiles: https://www.boost.org/doc/libs/1_75_0/doc/html/accumulators/user_s_guide.html#accumulators.user_s_guide.the_statistical_accumulators_library.p_square_quantile https://www.boost.org/doc/libs/1_75_0/doc/html/accumulators/user_s_guide.html#accumulators.user_s_guide.the_statistical_accumulators_library.extended_p_square https://www.boost.org/doc/libs/1_75_0/doc/html/accumulators/user_s_guide.html#accumulators.user_s_guide.the_statistical_accumulators_library.extended_p_square_quantile In particular, to compute both P90 and P99, together with min, max, mean, ..., just add the "extended_p_square" tag (or the "extended_p_square_quantile" tag) and specify probabilities 0.90 and 0.99 in the constructor: typedef accumulator_set<double, stats<tag::extended_p_square, tag::min, tag::max, tag::mean, tag::median, tag::sum > > acc_t; double probs[] = {0.90, 0.99); acc_t acc(extended_p_square_probabilities = probs); ... acc(value1); acc(value2); ... std::cout << "-- SUMMARY STATS:\n"; std::cout << "Min: " << min(acc) << "\n"; std::cout << "Max: " << max(acc) << "\n"; std::cout << "Mean: " << mean(acc) << "\n"; std::cout << "Median: " << median(acc) << "\n"; std::cout << "Sum: " << sum(acc) << "\n"; std::cout << "P90: " << extended_p_square(acc)[0] << "\n"; std::cout << "P99: " << extended_p_square(acc)[1] << "\n"; Hope this helps. Regards, Marco
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