Jacobi.hpp

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/*******************************************************************************
 * Copyright (C) 2017-2024 Theodore Chang
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
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 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
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#ifndef JACOBI_HPP
#define JACOBI_HPP
 
#include "Preconditioner.hpp"
 
template<sp_d data_t> class Jacobi final : public Preconditioner<data_t> {
    const Col<data_t> diag_reciprocal;
 
public:
    template<typename Container> explicit Jacobi(const Container& in_mat)
        : Preconditioner<data_t>()
        , diag_reciprocal(1. / Col<data_t>(in_mat.diag())) {}
 
    [[nodiscard]] Col<data_t> apply(const Col<data_t>&) override;
};
 
template<sp_d data_t> Col<data_t> Jacobi<data_t>::apply(const Col<data_t>& in) {
    Col<data_t> out = in;
 
    for(auto I = 0llu; I < in.n_elem; I += diag_reciprocal.n_elem) out.subvec(I, arma::size(diag_reciprocal)) %= diag_reciprocal;
 
    return out;
}
 
#endif