orangeinp/detail/SurfaceGridHash.hh

0001 //----------------------------------*-C++-*----------------------------------//
0002 // Copyright 2024 UT-Battelle, LLC, and other Celeritas developers.
0003 // See the top-level COPYRIGHT file for details.
0004 // SPDX-License-Identifier: (Apache-2.0 OR MIT)
0005 //---------------------------------------------------------------------------//
0006 //! \file orange/orangeinp/detail/SurfaceGridHash.hh
0007 //---------------------------------------------------------------------------//
0008 #pragma once
0009
0010 #include <cstdlib>
0011 #include <utility>
0012
0013 #include "corecel/Types.hh"
0014 #include "corecel/cont/Array.hh"
0015 #include "orange/OrangeTypes.hh"
0016
0017 namespace celeritas
0018 {
0019 namespace orangeinp
0020 {
0021 namespace detail
0022 {
0023 //---------------------------------------------------------------------------//
0024 /*!
0025  * Hash "similar" surfaces for faster lookups.
0026  *
0027  * This is meant to generate one or more "key" values for a hash of surfaces.
0028  *
0029  * This creates a hash map of local surfaces based on a characteristic
0030  * dimension (i.e. the radius of a sphere), which is used to accelerate surface
0031  * deduplication. For a given surface in bin N, possible duplicates may be
0032  * found in bins N-1, N, N+1.
0033  *
0034  * - Nearby surfaces should always have nearby "hash points", within some
0035  *   comparison tolerance.
0036  * - The comparison tolerance must be less than the grid width, probably \em
0037  *   much less.
0038  * - Different surfaces can have an identical hash point but have
0039  *   different surface types.
0040  * - The bin values will *always* be unique given a surface type.
0041  *
0042  * \sa LocalSurfaceInserter
0043  */
0044 class SurfaceGridHash
0045 {
0046   public:
0047     //!@{
0048     //! \name Type aliases
0049     using key_type = std::size_t;
0050     using result_type = Array<key_type, 2>;
0051     //!@}
0052
0053   public:
0054     // Construct with maximum tolerance and characteristic scale of grid
0055     SurfaceGridHash(real_type grid_scale, real_type tol);
0056
0057     // Construct keys for the grid
0058     result_type operator()(SurfaceType type, real_type hash_point) const;
0059
0060     //! Sentinel value for a hash point being redundant
0061     static constexpr key_type redundant() { return static_cast<key_type>(-1); }
0062
0063   private:
0064     real_type eps_;
0065     real_type grid_offset_;
0066     real_type inv_grid_width_;
0067
0068     // Calculate the bin of a new data point
0069     key_type calc_bin(SurfaceType type, real_type hash_point) const;
0070 };
0071
0072 //---------------------------------------------------------------------------//
0073 }  // namespace detail
0074 }  // namespace orangeinp
0075 }  // namespace celeritas