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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_BLAS_NRM2_HEADER
#define TEMPLATE_BLAS_NRM2_HEADER
template<class Treal>
Treal template_blas_nrm2(const integer *n, const Treal *x, const integer *incx)
{
/* The following loop is equivalent to this call to the LAPACK
auxiliary routine:
CALL DLASSQ( N, X, INCX, SCALE, SSQ ) */
/* System generated locals */
integer i__1, i__2;
Treal ret_val, d__1;
/* Local variables */
Treal norm, scale, absxi;
integer ix;
Treal ssq;
/* DNRM2 returns the euclidean norm of a vector via the function
name, so that
DNRM2 := sqrt( x'*x )
-- This version written on 25-October-1982.
Modified on 14-October-1993 to inline the call to DLASSQ.
Sven Hammarling, Nag Ltd.
Parameter adjustments */
--x;
/* Function Body */
if (*n < 1 || *incx < 1) {
norm = 0.;
} else if (*n == 1) {
norm = absMACRO(x[1]);
} else {
scale = 0.;
ssq = 1.;
i__1 = (*n - 1) * *incx + 1;
i__2 = *incx;
for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
if (x[ix] != 0.) {
absxi = (d__1 = x[ix], absMACRO(d__1));
if (scale < absxi) {
/* Computing 2nd power */
d__1 = scale / absxi;
ssq = ssq * (d__1 * d__1) + 1.;
scale = absxi;
} else {
/* Computing 2nd power */
d__1 = absxi / scale;
ssq += d__1 * d__1;
}
}
/* L10: */
}
norm = scale * template_blas_sqrt(ssq);
}
ret_val = norm;
return ret_val;
/* End of DNRM2. */
} /* dnrm2_ */
#endif
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