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/* Ergo, version 3.8.2, a program for linear scaling electronic structure
* calculations.
* Copyright (C) 2023 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
* and Anastasia Kruchinina.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Primary academic reference:
* Ergo: An open-source program for linear-scaling electronic structure
* calculations,
* Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
* Kruchinina,
* SoftwareX 7, 107 (2018),
* <http://dx.doi.org/10.1016/j.softx.2018.03.005>
*
* For further information about Ergo, see <http://www.ergoscf.org>.
*/
/* This file belongs to the template_lapack part of the Ergo source
* code. The source files in the template_lapack directory are modified
* versions of files originally distributed as CLAPACK, see the
* Copyright/license notice in the file template_lapack/COPYING.
*/
#ifndef TEMPLATE_LAPACK_ORG2L_HEADER
#define TEMPLATE_LAPACK_ORG2L_HEADER
template<class Treal>
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)
{
/* -- LAPACK routine (version 3.0) --
Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
Courant Institute, Argonne National Lab, and Rice University
February 29, 1992
Purpose
=======
DORG2L generates an m by n real matrix Q with orthonormal columns,
which is defined as the last n columns of a product of k elementary
reflectors of order m
Q = H(k) . . . H(2) H(1)
as returned by DGEQLF.
Arguments
=========
M (input) INTEGER
The number of rows of the matrix Q. M >= 0.
N (input) INTEGER
The number of columns of the matrix Q. M >= N >= 0.
K (input) INTEGER
The number of elementary reflectors whose product defines the
matrix Q. N >= K >= 0.
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the (n-k+i)-th column must contain the vector which
defines the elementary reflector H(i), for i = 1,2,...,k, as
returned by DGEQLF in the last k columns of its array
argument A.
On exit, the m by n matrix Q.
LDA (input) INTEGER
The first dimension of the array A. LDA >= max(1,M).
TAU (input) DOUBLE PRECISION array, dimension (K)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by DGEQLF.
WORK (workspace) DOUBLE PRECISION array, dimension (N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument has an illegal value
=====================================================================
Test the input arguments
Parameter adjustments */
/* Table of constant values */
integer c__1 = 1;
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
Treal d__1;
/* Local variables */
integer i__, j, l;
integer ii;
#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
a_dim1 = *lda;
a_offset = 1 + a_dim1 * 1;
a -= a_offset;
--tau;
--work;
/* Function Body */
*info = 0;
if (*m < 0) {
*info = -1;
} else if (*n < 0 || *n > *m) {
*info = -2;
} else if (*k < 0 || *k > *n) {
*info = -3;
} else if (*lda < maxMACRO(1,*m)) {
*info = -5;
}
if (*info != 0) {
i__1 = -(*info);
template_blas_erbla("ORG2L ", &i__1);
return 0;
}
/* Quick return if possible */
if (*n <= 0) {
return 0;
}
/* Initialise columns 1:n-k to columns of the unit matrix */
i__1 = *n - *k;
for (j = 1; j <= i__1; ++j) {
i__2 = *m;
for (l = 1; l <= i__2; ++l) {
a_ref(l, j) = 0.;
/* L10: */
}
a_ref(*m - *n + j, j) = 1.;
/* L20: */
}
i__1 = *k;
for (i__ = 1; i__ <= i__1; ++i__) {
ii = *n - *k + i__;
/* Apply H(i) to A(1:m-k+i,1:n-k+i) from the left */
a_ref(*m - *n + ii, ii) = 1.;
i__2 = *m - *n + ii;
i__3 = ii - 1;
template_lapack_larf("Left", &i__2, &i__3, &a_ref(1, ii), &c__1, &tau[i__], &a[
a_offset], lda, &work[1]);
i__2 = *m - *n + ii - 1;
d__1 = -tau[i__];
template_blas_scal(&i__2, &d__1, &a_ref(1, ii), &c__1);
a_ref(*m - *n + ii, ii) = 1. - tau[i__];
/* Set A(m-k+i+1:m,n-k+i) to zero */
i__2 = *m;
for (l = *m - *n + ii + 1; l <= i__2; ++l) {
a_ref(l, ii) = 0.;
/* L30: */
}
/* L40: */
}
return 0;
/* End of DORG2L */
} /* dorg2l_ */
#undef a_ref
#endif
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