105 lines
3.6 KiB
C++
105 lines
3.6 KiB
C++
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// Copyright 2015-2018 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_PROJECT_HPP
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#define BOOST_HISTOGRAM_ALGORITHM_PROJECT_HPP
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#include <algorithm>
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#include <boost/histogram/axis/variant.hpp>
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#include <boost/histogram/detail/detect.hpp>
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#include <boost/histogram/detail/make_default.hpp>
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#include <boost/histogram/detail/static_if.hpp>
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#include <boost/histogram/histogram.hpp>
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#include <boost/histogram/indexed.hpp>
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#include <boost/histogram/unsafe_access.hpp>
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#include <boost/mp11/list.hpp>
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#include <boost/mp11/set.hpp>
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#include <boost/mp11/utility.hpp>
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#include <boost/throw_exception.hpp>
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#include <stdexcept>
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#include <type_traits>
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#include <vector>
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namespace boost {
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namespace histogram {
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namespace algorithm {
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/**
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Returns a lower-dimensional histogram, summing over removed axes.
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Arguments are the source histogram and compile-time numbers, the remaining indices of
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the axes. Returns a new histogram which only contains the subset of axes. The source
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histogram is summed over the removed axes.
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*/
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template <class A, class S, unsigned N, typename... Ns>
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auto project(const histogram<A, S>& h, std::integral_constant<unsigned, N>, Ns...) {
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using LN = mp11::mp_list<std::integral_constant<unsigned, N>, Ns...>;
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static_assert(mp11::mp_is_set<LN>::value, "indices must be unique");
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const auto& old_axes = unsafe_access::axes(h);
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auto axes = detail::static_if<detail::is_tuple<A>>(
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[&](const auto& old_axes) {
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return std::make_tuple(std::get<N>(old_axes), std::get<Ns::value>(old_axes)...);
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},
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[&](const auto& old_axes) {
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return std::decay_t<decltype(old_axes)>({old_axes[N], old_axes[Ns::value]...});
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},
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old_axes);
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const auto& old_storage = unsafe_access::storage(h);
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using A2 = decltype(axes);
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auto result = histogram<A2, S>(std::move(axes), detail::make_default(old_storage));
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auto idx = detail::make_stack_buffer<int>(unsafe_access::axes(result));
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for (auto&& x : indexed(h, coverage::all)) {
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auto i = idx.begin();
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mp11::mp_for_each<LN>([&i, &x](auto J) { *i++ = x.index(J); });
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result.at(idx) += *x;
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}
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return result;
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}
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/**
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Returns a lower-dimensional histogram, summing over removed axes.
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This version accepts a source histogram and an iterable range containing the remaining
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indices.
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*/
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template <class A, class S, class Iterable, class = detail::requires_iterable<Iterable>>
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auto project(const histogram<A, S>& h, const Iterable& c) {
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using namespace boost::mp11;
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const auto& old_axes = unsafe_access::axes(h);
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// axes is always std::vector<...>, even if A is tuple
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auto axes = detail::make_empty_dynamic_axes(old_axes);
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axes.reserve(c.size());
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auto seen = detail::make_stack_buffer(old_axes, false);
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for (auto d : c) {
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if (static_cast<unsigned>(d) >= h.rank())
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BOOST_THROW_EXCEPTION(std::invalid_argument("invalid axis index"));
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if (seen[d]) BOOST_THROW_EXCEPTION(std::invalid_argument("indices are not unique"));
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seen[d] = true;
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axes.emplace_back(detail::axis_get(old_axes, d));
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}
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const auto& old_storage = unsafe_access::storage(h);
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auto result =
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histogram<decltype(axes), S>(std::move(axes), detail::make_default(old_storage));
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auto idx = detail::make_stack_buffer<int>(unsafe_access::axes(result));
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for (auto&& x : indexed(h, coverage::all)) {
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auto i = idx.begin();
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for (auto d : c) *i++ = x.index(d);
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result.at(idx) += *x;
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}
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return result;
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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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