ComputeResiduum.cpp

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "ComputeResiduum.h"
 
#include "MathLib/LinAlg/LinAlg.h"
 
namespace ProcessLib
{
GlobalVector computeResiduum(double const dt, GlobalVector const& x,
                             GlobalVector const& x_prev, GlobalMatrix const& M,
                             GlobalMatrix const& K, GlobalVector const& b)
{
    using namespace MathLib::LinAlg;
    GlobalVector residuum;
    GlobalVector x_dot;
    copy(x, x_dot);                        // tmp = x
    axpy(x_dot, -1., x_prev);              // tmp = x - x_prev
    scale(x_dot, 1. / dt);                 // tmp = (x - x_prev)/dt
    matMult(M, x_dot, residuum);           // r = M*x_dot
    matMultAdd(K, x, residuum, residuum);  // r = M*x_dot + K*x
    axpy(residuum, -1., b);                // r = M*x_dot + K*x - b
    scale(residuum, -1.);                  // r = -r
    return residuum;
}
}  // namespace ProcessLib