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template_lapack_org2l.h
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1 /* Ergo, version 3.7, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2018 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_ORG2L_HEADER
38 #define TEMPLATE_LAPACK_ORG2L_HEADER
39 
40 
41 template<class Treal>
42 int template_lapack_org2l(const integer *m, const integer *n, const integer *k, Treal *
43  a, const integer *lda, const Treal *tau, Treal *work, integer *info)
44 {
45 /* -- LAPACK routine (version 3.0) --
46  Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
47  Courant Institute, Argonne National Lab, and Rice University
48  February 29, 1992
49 
50 
51  Purpose
52  =======
53 
54  DORG2L generates an m by n real matrix Q with orthonormal columns,
55  which is defined as the last n columns of a product of k elementary
56  reflectors of order m
57 
58  Q = H(k) . . . H(2) H(1)
59 
60  as returned by DGEQLF.
61 
62  Arguments
63  =========
64 
65  M (input) INTEGER
66  The number of rows of the matrix Q. M >= 0.
67 
68  N (input) INTEGER
69  The number of columns of the matrix Q. M >= N >= 0.
70 
71  K (input) INTEGER
72  The number of elementary reflectors whose product defines the
73  matrix Q. N >= K >= 0.
74 
75  A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
76  On entry, the (n-k+i)-th column must contain the vector which
77  defines the elementary reflector H(i), for i = 1,2,...,k, as
78  returned by DGEQLF in the last k columns of its array
79  argument A.
80  On exit, the m by n matrix Q.
81 
82  LDA (input) INTEGER
83  The first dimension of the array A. LDA >= max(1,M).
84 
85  TAU (input) DOUBLE PRECISION array, dimension (K)
86  TAU(i) must contain the scalar factor of the elementary
87  reflector H(i), as returned by DGEQLF.
88 
89  WORK (workspace) DOUBLE PRECISION array, dimension (N)
90 
91  INFO (output) INTEGER
92  = 0: successful exit
93  < 0: if INFO = -i, the i-th argument has an illegal value
94 
95  =====================================================================
96 
97 
98  Test the input arguments
99 
100  Parameter adjustments */
101  /* Table of constant values */
102  integer c__1 = 1;
103 
104  /* System generated locals */
105  integer a_dim1, a_offset, i__1, i__2, i__3;
106  Treal d__1;
107  /* Local variables */
108  integer i__, j, l;
109  integer ii;
110 #define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
111 
112 
113  a_dim1 = *lda;
114  a_offset = 1 + a_dim1 * 1;
115  a -= a_offset;
116  --tau;
117  --work;
118 
119  /* Function Body */
120  *info = 0;
121  if (*m < 0) {
122  *info = -1;
123  } else if (*n < 0 || *n > *m) {
124  *info = -2;
125  } else if (*k < 0 || *k > *n) {
126  *info = -3;
127  } else if (*lda < maxMACRO(1,*m)) {
128  *info = -5;
129  }
130  if (*info != 0) {
131  i__1 = -(*info);
132  template_blas_erbla("ORG2L ", &i__1);
133  return 0;
134  }
135 
136 /* Quick return if possible */
137 
138  if (*n <= 0) {
139  return 0;
140  }
141 
142 /* Initialise columns 1:n-k to columns of the unit matrix */
143 
144  i__1 = *n - *k;
145  for (j = 1; j <= i__1; ++j) {
146  i__2 = *m;
147  for (l = 1; l <= i__2; ++l) {
148  a_ref(l, j) = 0.;
149 /* L10: */
150  }
151  a_ref(*m - *n + j, j) = 1.;
152 /* L20: */
153  }
154 
155  i__1 = *k;
156  for (i__ = 1; i__ <= i__1; ++i__) {
157  ii = *n - *k + i__;
158 
159 /* Apply H(i) to A(1:m-k+i,1:n-k+i) from the left */
160 
161  a_ref(*m - *n + ii, ii) = 1.;
162  i__2 = *m - *n + ii;
163  i__3 = ii - 1;
164  template_lapack_larf("Left", &i__2, &i__3, &a_ref(1, ii), &c__1, &tau[i__], &a[
165  a_offset], lda, &work[1]);
166  i__2 = *m - *n + ii - 1;
167  d__1 = -tau[i__];
168  template_blas_scal(&i__2, &d__1, &a_ref(1, ii), &c__1);
169  a_ref(*m - *n + ii, ii) = 1. - tau[i__];
170 
171 /* Set A(m-k+i+1:m,n-k+i) to zero */
172 
173  i__2 = *m;
174  for (l = *m - *n + ii + 1; l <= i__2; ++l) {
175  a_ref(l, ii) = 0.;
176 /* L30: */
177  }
178 /* L40: */
179  }
180  return 0;
181 
182 /* End of DORG2L */
183 
184 } /* dorg2l_ */
185 
186 #undef a_ref
187 
188 
189 #endif
int template_blas_scal(const integer *n, const Treal *da, Treal *dx, const integer *incx)
Definition: template_blas_scal.h:43
int integer
Definition: template_blas_common.h:40
#define maxMACRO(a, b)
Definition: template_blas_common.h:45
#define a_ref(a_1, a_2)
int template_blas_erbla(const char *srname, integer *info)
Definition: template_blas_common.cc:146
int template_lapack_larf(const char *side, const integer *m, const integer *n, const Treal *v, const integer *incv, const Treal *tau, Treal *c__, const integer *ldc, Treal *work)
Definition: template_lapack_larf.h:42
int template_lapack_org2l(const integer *m, const integer *n, const integer *k, Treal *a, const integer *lda, const Treal *tau, Treal *work, integer *info)
Definition: template_lapack_org2l.h:42