ergo
template_lapack_lapy2.h
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1 /* Ergo, version 3.4, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2014 Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek.
4  *
5  * This program is free software: you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation, either version 3 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
17  *
18  * Primary academic reference:
19  * Kohn−Sham Density Functional Theory Electronic Structure Calculations
20  * with Linearly Scaling Computational Time and Memory Usage,
21  * Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek,
22  * J. Chem. Theory Comput. 7, 340 (2011),
23  * <http://dx.doi.org/10.1021/ct100611z>
24  *
25  * For further information about Ergo, see <http://www.ergoscf.org>.
26  */
27 
28  /* This file belongs to the template_lapack part of the Ergo source
29  * code. The source files in the template_lapack directory are modified
30  * versions of files originally distributed as CLAPACK, see the
31  * Copyright/license notice in the file template_lapack/COPYING.
32  */
33 
34 
35 #ifndef TEMPLATE_LAPACK_LAPY2_HEADER
36 #define TEMPLATE_LAPACK_LAPY2_HEADER
37 
38 
39 template<class Treal>
40 Treal template_lapack_lapy2(Treal *x, Treal *y)
41 {
42 /* -- LAPACK auxiliary routine (version 3.0) --
43  Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
44  Courant Institute, Argonne National Lab, and Rice University
45  October 31, 1992
46 
47 
48  Purpose
49  =======
50 
51  DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
52  overflow.
53 
54  Arguments
55  =========
56 
57  X (input) DOUBLE PRECISION
58  Y (input) DOUBLE PRECISION
59  X and Y specify the values x and y.
60 
61  ===================================================================== */
62  /* System generated locals */
63  Treal ret_val, d__1;
64  /* Local variables */
65  Treal xabs, yabs, w, z__;
66 
67 
68 
69  xabs = absMACRO(*x);
70  yabs = absMACRO(*y);
71  w = maxMACRO(xabs,yabs);
72  z__ = minMACRO(xabs,yabs);
73  if (z__ == 0.) {
74  ret_val = w;
75  } else {
76 /* Computing 2nd power */
77  d__1 = z__ / w;
78  ret_val = w * template_blas_sqrt(d__1 * d__1 + 1.);
79  }
80  return ret_val;
81 
82 /* End of DLAPY2 */
83 
84 } /* dlapy2_ */
85 
86 #endif
#define absMACRO(x)
Definition: template_blas_common.h:45
Treal template_lapack_lapy2(Treal *x, Treal *y)
Definition: template_lapack_lapy2.h:40
#define maxMACRO(a, b)
Definition: template_blas_common.h:43
#define minMACRO(a, b)
Definition: template_blas_common.h:44
Treal template_blas_sqrt(Treal x)