unm2r.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_UNM2R_HH
#define TLAPACK_UNM2R_HH
 
#include "tlapack/base/utils.hpp"
#include "tlapack/lapack/unmq_level2.hpp"
 
namespace tlapack {
 
template <class T,
          TLAPACK_SMATRIX matrixA_t,
          TLAPACK_SMATRIX matrixC_t,
          TLAPACK_VECTOR tau_t,
          TLAPACK_SIDE side_t,
          TLAPACK_OP trans_t>
constexpr WorkInfo unm2r_worksize(side_t side,
                                  trans_t trans,
                                  const matrixA_t& A,
                                  const tau_t& tau,
                                  const matrixC_t& C)
{
    using idx_t = size_type<matrixA_t>;
    using range = pair<idx_t, idx_t>;
 
    // constants
    const idx_t m = nrows(C);
    const idx_t n = ncols(C);
    const idx_t nA = (side == Side::Left) ? m : n;
 
    auto&& v = slice(A, range{0, nA}, 0);
    return larf_worksize<T>(side, FORWARD, COLUMNWISE_STORAGE, v, tau[0], C);
}
 
template <TLAPACK_SMATRIX matrixA_t,
          TLAPACK_SMATRIX matrixC_t,
          TLAPACK_VECTOR tau_t,
          TLAPACK_SIDE side_t,
          TLAPACK_OP trans_t>
int unm2r(side_t side,
          trans_t trans,
          const matrixA_t& A,
          const tau_t& tau,
          matrixC_t& C)
{
    using idx_t = size_type<matrixA_t>;
    using work_t = matrix_type<matrixA_t, matrixC_t>;
    using T = type_t<work_t>;
 
    // Functor
    Create<work_t> new_matrix;
 
    // constants
    const idx_t m = nrows(C);
    const idx_t n = ncols(C);
    const idx_t k = size(tau);
 
    // quick return
    if ((m == 0) || (n == 0) || (k == 0)) return 0;
 
    // Allocates workspace
    WorkInfo workinfo = unm2r_worksize<T>(side, trans, A, tau, C);
    std::vector<T> work_;
    auto work = new_matrix(work_, workinfo.m, workinfo.n);
 
    return unmq_level2_work(side, trans, FORWARD, COLUMNWISE_STORAGE, A, tau, C,
                            work);
}
 
}  // namespace tlapack
 
#endif  // TLAPACK_UNM2R_HH