hemm.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_HEMM_HH
#define TLAPACK_LEGACY_HEMM_HH
 
#include "tlapack/blas/hemm.hpp"
#include "tlapack/legacy_api/base/types.hpp"
#include "tlapack/legacy_api/base/utils.hpp"
 
namespace tlapack {
namespace legacy {
 
    template <typename TA, typename TB, typename TC>
    void hemm(Layout layout,
              Side side,
              Uplo uplo,
              idx_t m,
              idx_t n,
              scalar_type<TA, TB, TC> alpha,
              TA const* A,
              idx_t lda,
              TB const* B,
              idx_t ldb,
              scalar_type<TA, TB, TC> beta,
              TC* C,
              idx_t ldc)
    {
        using internal::create_matrix;
        using scalar_t = scalar_type<TA, TB, TC>;
 
        // check arguments
        tlapack_check_false(layout != Layout::ColMajor &&
                            layout != Layout::RowMajor);
        tlapack_check_false(side != Side::Left && side != Side::Right);
        tlapack_check_false(uplo != Uplo::Lower && uplo != Uplo::Upper &&
                            uplo != Uplo::General);
        tlapack_check_false(m < 0);
        tlapack_check_false(n < 0);
        tlapack_check_false(lda < ((side == Side::Left) ? m : n));
        tlapack_check_false(ldb < ((layout == Layout::RowMajor) ? n : m));
        tlapack_check_false(ldc < ((layout == Layout::RowMajor) ? n : m));
 
        // quick return
        if (m == 0 || n == 0 ||
            ((alpha == scalar_t(0)) && (beta == scalar_t(1))))
            return;
 
        // adapt if row major
        if (layout == Layout::RowMajor) {
            side = (side == Side::Left) ? Side::Right : Side::Left;
            if (uplo == Uplo::Lower)
                uplo = Uplo::Upper;
            else if (uplo == Uplo::Upper)
                uplo = Uplo::Lower;
            std::swap(m, n);
        }
 
        // Matrix views
        const auto A_ = (side == Side::Left)
                            ? create_matrix<TA>((TA*)A, m, m, lda)
                            : create_matrix<TA>((TA*)A, n, n, lda);
        const auto B_ = create_matrix<TB>((TB*)B, m, n, ldb);
        auto C_ = create_matrix<TC>(C, m, n, ldc);
 
        if (alpha == scalar_t(0)) {
            if (beta == scalar_t(0)) {
                for (idx_t j = 0; j < n; ++j)
                    for (idx_t i = 0; i < m; ++i)
                        C_(i, j) = TC(0);
            }
            else {
                for (idx_t j = 0; j < n; ++j)
                    for (idx_t i = 0; i < m; ++i)
                        C_(i, j) *= beta;
            }
        }
        else {
            if (beta == scalar_t(0))
                hemm(side, uplo, alpha, A_, B_, C_);
            else
                hemm(side, uplo, alpha, A_, B_, beta, C_);
        }
    }
 
}  // namespace legacy
}  // namespace tlapack
 
#endif  //  #ifndef TLAPACK_LEGACY_HEMM_HH