CovarianceMatrix.H

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/* Copyright 2022-2026 The Regents of the University of California, through Lawrence
 *           Berkeley National Laboratory (subject to receipt of any required
 *           approvals from the U.S. Dept. of Energy). All rights reserved.
 *
 * This file is part of ImpactX.
 *
 * Authors: Chad Mitchell, Axel Huebl
 * License: BSD-3-Clause-LBNL
 */
#ifndef IMPACTX_DISTRIBUTION_COVARIANCE_MATRIX_H
#define IMPACTX_DISTRIBUTION_COVARIANCE_MATRIX_H
 
#include <AMReX_REAL.H>
#include <AMReX_SmallMatrix.H>
 
 
namespace impactx
{
    using Map6x6 = amrex::SmallMatrix<amrex::ParticleReal, 6, 6, amrex::Order::F, 1>;

    using CovarianceMatrix = Map6x6;

    inline Map6x6 symplectic_form ()
    {
        Map6x6 Omega = Map6x6::Zero();
        for (int i = 0; i < 3; ++i) {
            Omega(2*i+1, 2*i+2) =  1;
            Omega(2*i+2, 2*i+1) = -1;
        }
        return Omega;
    }
 

    struct Envelope
    {
        CovarianceMatrix m_env; 
        amrex::ParticleReal m_beam_intensity = 0.0; 
 
        Envelope () = default;
 
        Envelope (
            CovarianceMatrix const & env,
            amrex::ParticleReal const beam_intensity
        )
          : m_env(env), m_beam_intensity(beam_intensity)
        {
        }

        Envelope &
        set_beam_intensity (amrex::ParticleReal const intensity)
        {
            m_beam_intensity = intensity;
 
            return *this;
         }

        amrex::ParticleReal
        beam_intensity () const
        {
            return m_beam_intensity;
        }

        Envelope &
        set_covariance_matrix (CovarianceMatrix const & covariance_matrix)
        {
            m_env = covariance_matrix;
 
            return *this;
         }

        CovarianceMatrix
        covariance_matrix () const
        {
            return m_env;
        }
 
    };
 
 
} // namespace impactx::distribution
 
#endif // IMPACTX_DISTRIBUTION_COVARIANCE_MATRIX_H