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