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Add a helper class to find the grid value corresponding to a sampled …
…CDF value
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| //----------------------------------*-C++-*----------------------------------// | ||
| // Copyright 2024 UT-Battelle, LLC, and other Celeritas developers. | ||
| // See the top-level COPYRIGHT file for details. | ||
| // SPDX-License-Identifier: (Apache-2.0 OR MIT) | ||
| //---------------------------------------------------------------------------// | ||
| //! \file celeritas/grid/InverseCdfFinder.hh | ||
| //---------------------------------------------------------------------------// | ||
| #pragma once | ||
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| #include "corecel/Assert.hh" | ||
| #include "corecel/Macros.hh" | ||
| #include "corecel/cont/Range.hh" | ||
| #include "corecel/grid/Interpolator.hh" | ||
| #include "corecel/math/Algorithms.hh" | ||
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| namespace celeritas | ||
| { | ||
| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Given a sampled CDF value, find the corresponding grid value. | ||
| * | ||
| * \tparam G Grid, e.g. \c UniformGrid or \c NonUniformGrid | ||
| * \tparam C Calculate the CDF at a given grid index | ||
| * | ||
| * Both the input grid and the CDF must be monotonically increasing. The | ||
| * sampled CDF value must be in range. | ||
| */ | ||
| template<class G, class C> | ||
| class InverseCdfFinder | ||
| { | ||
| public: | ||
| // Construct from grid and CDF calculator | ||
| inline CELER_FUNCTION InverseCdfFinder(G const& grid, C&& calc_cdf); | ||
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| // Find and interpolate the grid value corresponding to the given CDF | ||
| inline CELER_FUNCTION real_type operator()(real_type cdf) const; | ||
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| private: | ||
| G const& grid_; | ||
| C calc_cdf_; | ||
| }; | ||
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| //---------------------------------------------------------------------------// | ||
| // INLINE DEFINITIONS | ||
| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Construct from grid and CDF calculator. | ||
| */ | ||
| template<class G, class C> | ||
| CELER_FUNCTION | ||
| InverseCdfFinder<G, C>::InverseCdfFinder(G const& grid, C&& calc_cdf) | ||
| : grid_(grid), calc_cdf_(celeritas::forward<C>(calc_cdf)) | ||
| { | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Find and interpolate the grid value corresponding to the given CDF. | ||
| */ | ||
| template<class G, class C> | ||
| CELER_FUNCTION real_type InverseCdfFinder<G, C>::operator()(real_type cdf) const | ||
| { | ||
| CELER_EXPECT(cdf >= 0 && cdf < 1); | ||
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| // Find the grid index of the sampled CDF value | ||
| Range indices(grid_.size()); | ||
| auto iter = celeritas::lower_bound( | ||
| indices.begin(), indices.end(), cdf, [this](size_type i, real_type c) { | ||
| return calc_cdf_(i) < c; | ||
| }); | ||
| CELER_ASSERT(iter != indices.end()); | ||
| if (calc_cdf_(*iter) != cdf) | ||
| { | ||
| --iter; | ||
| } | ||
| size_type i = iter - indices.begin(); | ||
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| // Calculate the grid value corresponding to the sampled CDF value | ||
| return LinearInterpolator<real_type>{ | ||
| {calc_cdf_(i), grid_[i]}, {calc_cdf_(i + 1), grid_[i + 1]}}(cdf); | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| } // namespace celeritas |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,56 @@ | ||
| //----------------------------------*-C++-*----------------------------------// | ||
| // Copyright 2024 UT-Battelle, LLC, and other Celeritas developers. | ||
| // See the top-level COPYRIGHT file for details. | ||
| // SPDX-License-Identifier: (Apache-2.0 OR MIT) | ||
| //---------------------------------------------------------------------------// | ||
| //! \file celeritas/grid/InverseCdfFinder.test.cc | ||
| //---------------------------------------------------------------------------// | ||
| #include "celeritas/grid/InverseCdfFinder.hh" | ||
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| #include "corecel/data/Collection.hh" | ||
| #include "corecel/data/CollectionBuilder.hh" | ||
| #include "corecel/grid/NonuniformGrid.hh" | ||
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| #include "celeritas_test.hh" | ||
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| namespace celeritas | ||
| { | ||
| namespace test | ||
| { | ||
| //---------------------------------------------------------------------------// | ||
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| class InverseCdfFinderTest : public Test | ||
| { | ||
| protected: | ||
| using GridT = NonuniformGrid<real_type>; | ||
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| void SetUp() override | ||
| { | ||
| CollectionBuilder build(&data); | ||
| values = build.insert_back({0.0, 0.2, 0.5, 1.5, 6.0, 10.0}); | ||
| ref = data; | ||
| } | ||
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| ItemRange<real_type> values; | ||
| Collection<real_type, Ownership::value, MemSpace::host> data; | ||
| Collection<real_type, Ownership::const_reference, MemSpace::host> ref; | ||
| }; | ||
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| TEST_F(InverseCdfFinderTest, all) | ||
| { | ||
| GridT grid(values, ref); | ||
| std::vector<real_type> cdf{0.0, 0.1, 0.2, 0.8, 0.9, 1.0}; | ||
| InverseCdfFinder find(grid, [&cdf](size_type i) { return cdf[i]; }); | ||
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| EXPECT_SOFT_EQ(0, find(0)); | ||
| EXPECT_SOFT_EQ(0.1, find(0.05)); | ||
| EXPECT_SOFT_EQ(0.2, find(0.1)); | ||
| EXPECT_SOFT_EQ(1, find(0.5)); | ||
| EXPECT_SOFT_EQ(6.0, find(0.9)); | ||
| EXPECT_SOFT_EQ(8.0, find(0.95)); | ||
| EXPECT_SOFT_EQ(9.99996, find(0.999999)); | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| } // namespace test | ||
| } // namespace celeritas |