/* blas/source_nrm2_r.h

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman

 * 

 * 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, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

{

  BASE scale = 0.0;

  BASE ssq = 1.0;

  INDEX i;

  INDEX ix = 0;

  if (N <= 0 || incX <= 0) {

    return 0;

  } else if (N == 1) {

    return fabs(X[0]);

  }

  for (i = 0; i < N; i++) {

    const BASE x = X[ix];

    if (x != 0.0) {

      const BASE ax = fabs(x);

      if (scale < ax) {

        ssq = 1.0 + ssq * (scale / ax) * (scale / ax);

        scale = ax;

      } else {

        ssq += (ax / scale) * (ax / scale);

      }

    }

    ix += incX;

  }

  return scale * sqrt(ssq);

}