getri_uili.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_getri_uili_HH
#define TLAPACK_getri_uili_HH
 
#include "tlapack/base/utils.hpp"
#include "tlapack/blas/gemm.hpp"
#include "tlapack/lapack/trtri_recursive.hpp"
#include "tlapack/lapack/ul_mult.hpp"
 
namespace tlapack {
 
template <TLAPACK_MATRIX matrix_t>
int getri_uili(matrix_t& A)
{
    // check arguments
    tlapack_check(nrows(A) == ncols(A));
 
    // Invert the upper part of A; U
    int info = trtri_recursive(UPPER_TRIANGLE, NON_UNIT_DIAG, A);
    if (info != 0) return info;
 
    // Invert the lower part of A; L which has 1 on the diagonal
    trtri_recursive(LOWER_TRIANGLE, UNIT_DIAG, A);
 
    // multiply U^{-1} and L^{-1} in place using ul_mult
    ul_mult(A);
 
    return 0;
 
}  // getri_uili
 
}  // namespace tlapack
 
#endif  // TLAPACK_getri_uili_HH