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- // Copyright 2015-2018 Hans Dembinski
- //
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE_1_0.txt
- // or copy at http://www.boost.org/LICENSE_1_0.txt)
- //[ guide_custom_storage
- #include <algorithm> // std::for_each
- #include <array>
- #include <boost/histogram.hpp>
- #include <boost/histogram/algorithm/sum.hpp>
- #include <functional> // std::ref
- #include <unordered_map>
- #include <vector>
- int main() {
- using namespace boost::histogram;
- const auto axis = axis::regular<>(10, 0.0, 1.0);
- auto data = {0.1, 0.3, 0.2, 0.7};
- // Create static histogram with vector<int> as counter storage, you can use
- // other arithmetic types as counters, e.g. double.
- auto h1 = make_histogram_with(std::vector<int>(), axis);
- std::for_each(data.begin(), data.end(), std::ref(h1));
- assert(algorithm::sum(h1) == 4);
- // Create static histogram with array<int, N> as counter storage which is
- // allocated completely on the stack (this is very fast). N may be larger than
- // the actual number of bins used; an exception is raised if N is too small to
- // hold all bins.
- auto h2 = make_histogram_with(std::array<int, 12>(), axis);
- std::for_each(data.begin(), data.end(), std::ref(h2));
- assert(algorithm::sum(h2) == 4);
- // Create static histogram with unordered_map as counter storage; this
- // generates a sparse histogram where only memory is allocated for bins that
- // are non-zero. This sounds like a good idea for high-dimensional histograms,
- // but maps come with a memory and run-time overhead. The default_storage
- // usually performs better in high dimensions.
- auto h3 = make_histogram_with(std::unordered_map<std::size_t, int>(), axis);
- std::for_each(data.begin(), data.end(), std::ref(h3));
- assert(algorithm::sum(h3) == 4);
- }
- //]
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