corecel/math/TridiagonalSolver.hh

0001 //------------------------------- -*- C++ -*- -------------------------------//
0002 // Copyright Celeritas contributors: see top-level COPYRIGHT file for details
0003 // SPDX-License-Identifier: (Apache-2.0 OR MIT)
0004 //---------------------------------------------------------------------------//
0005 //! \file corecel/math/TridiagonalSolver.hh
0006 //---------------------------------------------------------------------------//
0007 #pragma once
0008
0009 #include <vector>
0010
0011 #include "corecel/Assert.hh"
0012 #include "corecel/Macros.hh"
0013 #include "corecel/Types.hh"
0014 #include "corecel/cont/Span.hh"
0015
0016 namespace celeritas
0017 {
0018 //---------------------------------------------------------------------------//
0019 /*!
0020  * Solve a tridiagonal system of equations using the Thomas algorithm.
0021  *
0022  * This is a simplified form of Gaussian elimination that can solve a
0023  * tridiagonal system \f$ \mathbf{T} \mathbf{x} = \mathbf{b} \f$ in O(n) time.
0024  */
0025 class TridiagonalSolver
0026 {
0027   public:
0028     //!@{
0029     //! \name Type aliases
0030     using Real3 = Array<real_type, 3>;
0031     using Coeffs = std::vector<Real3>;
0032     using SpanConstReal = Span<real_type const>;
0033     using SpanReal = Span<real_type>;
0034     //!@}
0035
0036   public:
0037     // Construct with coefficients
0038     explicit TridiagonalSolver(Coeffs&& tridiag);
0039
0040     // Solve the tridiagonal system
0041     void operator()(SpanConstReal rhs, SpanReal x) const;
0042
0043   private:
0044     Coeffs tridiag_;
0045 };
0046
0047 //---------------------------------------------------------------------------//
0048 }  // namespace celeritas