trsv.hpp

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//
// Copyright (c) 2017-2021, University of Tennessee. All rights reserved.
// 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_LEGACY_TRSV_HH
#define TLAPACK_LEGACY_TRSV_HH
 
#include "tlapack/blas/trsv.hpp"
#include "tlapack/legacy_api/base/types.hpp"
#include "tlapack/legacy_api/base/utils.hpp"
 
namespace tlapack {
namespace legacy {
 
    template <typename TA, typename TX>
    void trsv(Layout layout,
              Uplo uplo,
              Op trans,
              Diag diag,
              idx_t n,
              TA const* A,
              idx_t lda,
              TX* x,
              int_t incx)
    {
        using internal::create_matrix;
 
        // check arguments
        tlapack_check_false(layout != Layout::ColMajor &&
                            layout != Layout::RowMajor);
        tlapack_check_false(uplo != Uplo::Lower && uplo != Uplo::Upper);
        tlapack_check_false(trans != Op::NoTrans && trans != Op::Trans &&
                            trans != Op::ConjTrans);
        tlapack_check_false(diag != Diag::NonUnit && diag != Diag::Unit);
        tlapack_check_false(n < 0);
        tlapack_check_false(lda < n);
        tlapack_check_false(incx == 0);
 
        // quick return
        if (n == 0) return;
 
        // for row major, swap lower <=> upper and
        // A => A^T; A^T => A; A^H => A & doConj
        bool doConj = false;
        if (layout == Layout::RowMajor) {
            uplo = (uplo == Uplo::Lower ? Uplo::Upper : Uplo::Lower);
            if (trans == Op::NoTrans)
                trans = Op::Trans;
            else {
                if (trans == Op::ConjTrans) doConj = true;
                trans = Op::NoTrans;
            }
        }
 
        // Conjugate if A is row-major and initially trans is Op::ConjTrans
        if (doConj) {
            for (idx_t i = 0; i < n; ++i)
                x[i * abs(incx)] = conj(x[i * abs(incx)]);
        }
 
        // Matrix views
        const auto A_ = create_matrix<TA>((TA*)A, n, n, lda);
 
        tlapack_expr_with_vector(x_, TX, n, x, incx,
                                 trsv(uplo, trans, diag, A_, x_));
 
        // Conjugate if A is row-major and initially trans is Op::ConjTrans
        if (doConj) {
            for (idx_t i = 0; i < n; ++i)
                x[i * abs(incx)] = conj(x[i * abs(incx)]);
        }
    }
 
}  // namespace legacy
}  // namespace tlapack
 
#endif  //  #ifndef TLAPACK_LEGACY_TRSV_HH