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template_lapack_ladiv.h
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1/* Ergo, version 3.8.2, a program for linear scaling electronic structure
2 * calculations.
3 * Copyright (C) 2023 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
4 * and Anastasia Kruchinina.
5 *
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 *
19 * Primary academic reference:
20 * Ergo: An open-source program for linear-scaling electronic structure
21 * calculations,
22 * Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
23 * Kruchinina,
24 * SoftwareX 7, 107 (2018),
25 * <http://dx.doi.org/10.1016/j.softx.2018.03.005>
26 *
27 * For further information about Ergo, see <http://www.ergoscf.org>.
28 */
29
30 /* This file belongs to the template_lapack part of the Ergo source
31 * code. The source files in the template_lapack directory are modified
32 * versions of files originally distributed as CLAPACK, see the
33 * Copyright/license notice in the file template_lapack/COPYING.
34 */
35
36
37#ifndef TEMPLATE_LAPACK_LADIV_HEADER
38#define TEMPLATE_LAPACK_LADIV_HEADER
39
40
41template<class Treal>
42int template_lapack_ladiv(const Treal *a, const Treal *b, const Treal *c__,
43 const Treal *d__, Treal *p, Treal *q)
44{
45/* -- LAPACK auxiliary routine (version 3.0) --
46 Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
47 Courant Institute, Argonne National Lab, and Rice University
48 October 31, 1992
49
50
51 Purpose
52 =======
53
54 DLADIV performs complex division in real arithmetic
55
56 a + i*b
57 p + i*q = ---------
58 c + i*d
59
60 The algorithm is due to Robert L. Smith and can be found
61 in D. Knuth, The art of Computer Programming, Vol.2, p.195
62
63 Arguments
64 =========
65
66 A (input) DOUBLE PRECISION
67 B (input) DOUBLE PRECISION
68 C (input) DOUBLE PRECISION
69 D (input) DOUBLE PRECISION
70 The scalars a, b, c, and d in the above expression.
71
72 P (output) DOUBLE PRECISION
73 Q (output) DOUBLE PRECISION
74 The scalars p and q in the above expression.
75
76 ===================================================================== */
77 Treal e, f;
78
79
80
81 if (absMACRO(*d__) < absMACRO(*c__)) {
82 e = *d__ / *c__;
83 f = *c__ + *d__ * e;
84 *p = (*a + *b * e) / f;
85 *q = (*b - *a * e) / f;
86 } else {
87 e = *c__ / *d__;
88 f = *d__ + *c__ * e;
89 *p = (*b + *a * e) / f;
90 *q = (-(*a) + *b * e) / f;
91 }
92
93 return 0;
94
95/* End of DLADIV */
96
97} /* dladiv_ */
98
99#endif
#define absMACRO(x)
Definition template_blas_common.h:47
int template_lapack_ladiv(const Treal *a, const Treal *b, const Treal *c__, const Treal *d__, Treal *p, Treal *q)
Definition template_lapack_ladiv.h:42