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/* Ergo, version 3.8, a program for linear scaling electronic structure
* calculations.
* Copyright (C) 2019 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_TRTI2_HEADER
#define TEMPLATE_LAPACK_TRTI2_HEADER
template<class Treal>
int template_lapack_trti2(const char *uplo, const char *diag, const integer *n, Treal *
a, const integer *lda, 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
=======
DTRTI2 computes the inverse of a real upper or lower triangular
matrix.
This is the Level 2 BLAS version of the algorithm.
Arguments
=========
UPLO (input) CHARACTER*1
Specifies whether the matrix A is upper or lower triangular.
= 'U': Upper triangular
= 'L': Lower triangular
DIAG (input) CHARACTER*1
Specifies whether or not the matrix A is unit triangular.
= 'N': Non-unit triangular
= 'U': Unit triangular
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the triangular matrix A. If UPLO = 'U', the
leading n by n upper triangular part of the array A contains
the upper triangular matrix, and the strictly lower
triangular part of A is not referenced. If UPLO = 'L', the
leading n by n lower triangular part of the array A contains
the lower triangular matrix, and the strictly upper
triangular part of A is not referenced. If DIAG = 'U', the
diagonal elements of A are also not referenced and are
assumed to be 1.
On exit, the (triangular) inverse of the original matrix, in
the same storage format.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -k, the k-th argument had an illegal value
=====================================================================
Test the input parameters.
Parameter adjustments */
/* Table of constant values */
integer c__1 = 1;
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
/* Local variables */
integer j;
logical upper;
logical nounit;
Treal ajj;
#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;
/* Function Body */
*info = 0;
upper = template_blas_lsame(uplo, "U");
nounit = template_blas_lsame(diag, "N");
if (! upper && ! template_blas_lsame(uplo, "L")) {
*info = -1;
} else if (! nounit && ! template_blas_lsame(diag, "U")) {
*info = -2;
} else if (*n < 0) {
*info = -3;
} else if (*lda < maxMACRO(1,*n)) {
*info = -5;
}
if (*info != 0) {
i__1 = -(*info);
template_blas_erbla("TRTI2 ", &i__1);
return 0;
}
if (upper) {
/* Compute inverse of upper triangular matrix. */
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (nounit) {
a_ref(j, j) = 1. / a_ref(j, j);
ajj = -a_ref(j, j);
} else {
ajj = -1.;
}
/* Compute elements 1:j-1 of j-th column. */
i__2 = j - 1;
template_blas_trmv("Upper", "No transpose", diag, &i__2, &a[a_offset], lda, &
a_ref(1, j), &c__1);
i__2 = j - 1;
template_blas_scal(&i__2, &ajj, &a_ref(1, j), &c__1);
/* L10: */
}
} else {
/* Compute inverse of lower triangular matrix. */
for (j = *n; j >= 1; --j) {
if (nounit) {
a_ref(j, j) = 1. / a_ref(j, j);
ajj = -a_ref(j, j);
} else {
ajj = -1.;
}
if (j < *n) {
/* Compute elements j+1:n of j-th column. */
i__1 = *n - j;
template_blas_trmv("Lower", "No transpose", diag, &i__1, &a_ref(j + 1, j
+ 1), lda, &a_ref(j + 1, j), &c__1);
i__1 = *n - j;
template_blas_scal(&i__1, &ajj, &a_ref(j + 1, j), &c__1);
}
/* L20: */
}
}
return 0;
/* End of DTRTI2 */
} /* dtrti2_ */
#undef a_ref
#endif
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