// Copyright 2018 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
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#define BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
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#include <boost/histogram/accumulators/sum.hpp>
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#include <boost/histogram/fwd.hpp>
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#include <boost/histogram/indexed.hpp>
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#include <boost/mp11/utility.hpp>
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#include <type_traits>
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namespace boost {
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namespace histogram {
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namespace algorithm {
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/** Compute the sum over all histogram cells (underflow/overflow included by default).
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The implementation favors accuracy and protection against overflow over speed. If the
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value type of the histogram is an integral or floating point type,
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accumulators::sum<double> is used to compute the sum, else the original value type is
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used. Compilation fails, if the value type does not support operator+=. The return type
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is double if the value type of the histogram is integral or floating point, and the
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original value type otherwise.
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If you need a different trade-off, you can write your own loop or use `std::accumulate`:
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```
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// iterate over all bins
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auto sum_all = std::accumulate(hist.begin(), hist.end(), 0.0);
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// skip underflow/overflow bins
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double sum = 0;
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for (auto&& x : indexed(hist))
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sum += *x; // dereference accessor
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// or:
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// auto ind = boost::histogram::indexed(hist);
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// auto sum = std::accumulate(ind.begin(), ind.end(), 0.0);
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```
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@returns accumulator type or double
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@param hist Const reference to the histogram.
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@param cov Iterate over all or only inner bins (optional, default: all).
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*/
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template <class A, class S>
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auto sum(const histogram<A, S>& hist, const coverage cov = coverage::all) {
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using T = typename histogram<A, S>::value_type;
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using sum_type = mp11::mp_if<std::is_arithmetic<T>, accumulators::sum<double>, T>;
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sum_type sum;
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if (cov == coverage::all)
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for (auto&& x : hist) sum += x;
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else
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// sum += x also works if sum_type::operator+=(const sum_type&) exists
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for (auto&& x : indexed(hist)) sum += *x;
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using R = mp11::mp_if<std::is_arithmetic<T>, double, T>;
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return static_cast<R>(sum);
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}
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} // namespace algorithm
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} // namespace histogram
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} // namespace boost
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#endif
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