lacpy.hpp

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//
// Copyright (c) 2025, University of Colorado Denver. All rights reserved.
//
// This file is part of <T>LAPACK.
// <T>LAPACK is free software: you can redistribute it and/or modify it under
// the terms of the BSD 3-Clause license. See the accompanying LICENSE file.
 
#ifndef TLAPACK_LACPY_HH
#define TLAPACK_LACPY_HH
 
#include "tlapack/base/types.hpp"
 
namespace tlapack {
 
template <TLAPACK_UPLO uplo_t,
          TLAPACK_MATRIX matrixA_t,
          TLAPACK_MATRIX matrixB_t>
void lacpy(uplo_t uplo, const matrixA_t& A, matrixB_t& B)
{
    // data traits
    using idx_t = size_type<matrixA_t>;
    using TB = type_t<matrixB_t>;
 
    // constants
    const idx_t m = nrows(A);
    const idx_t n = ncols(A);
 
    // check arguments
    tlapack_check_false(uplo != Uplo::Lower && uplo != Uplo::Upper &&
                        uplo != Uplo::General);
 
    if (uplo == Uplo::Upper) {
        // Set the strictly upper triangular or trapezoidal part of B
        for (idx_t j = 0; j < n; ++j) {
            const idx_t M = min(m, j + 1);
            for (idx_t i = 0; i < M; ++i)
                B(i, j) = (TB)A(i, j);
        }
    }
    else if (uplo == Uplo::Lower) {
        // Set the strictly lower triangular or trapezoidal part of B
        const idx_t N = min(m, n);
        for (idx_t j = 0; j < N; ++j)
            for (idx_t i = j; i < m; ++i)
                B(i, j) = (TB)A(i, j);
    }
    else {
        // Set the whole m-by-n matrix B
        for (idx_t j = 0; j < n; ++j)
            for (idx_t i = 0; i < m; ++i)
                B(i, j) = (TB)A(i, j);
    }
}
 
}  // namespace tlapack
 
#endif  // TLAPACK_LACPY_HH