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/* ---------------------------------------------------------------------
*
* -- Automatically Tuned Linear Algebra Software (ATLAS)
* (C) Copyright 2000 All Rights Reserved
*
* -- ATLAS routine -- Version 3.9.24 -- December 25, 2000
*
* Author : Antoine P. Petitet
* Originally developed at the University of Tennessee,
* Innovative Computing Laboratory, Knoxville TN, 37996-1301, USA.
*
* ---------------------------------------------------------------------
*
* -- Copyright notice and Licensing terms:
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions, and the following disclaimer in
* the documentation and/or other materials provided with the distri-
* bution.
* 3. The name of the University, the ATLAS group, or the names of its
* contributors may not be used to endorse or promote products deri-
* ved from this software without specific written permission.
*
* -- Disclaimer:
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEO-
* RY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (IN-
* CLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ---------------------------------------------------------------------
*/
/*
* Include files
*/
#include "atlas_refmisc.h"
#include "atlas_reflevel1.h"
float ATL_srefnrm2
(
const int N,
const float * X,
const int INCX
)
{
/*
* Purpose
* =======
*
* ATL_srefnrm2 returns the 2-norm of an n-vector x.
*
* Arguments
* =========
*
* N (input) const int
* On entry, N specifies the length of the vector x. N must be
* at least zero. Unchanged on exit.
*
* X (input) const float *
* On entry, X points to the first entry to be accessed of an
* incremented array of size equal to or greater than
* ( 1 + ( n - 1 ) * abs( INCX ) ) * sizeof( float ),
* that contains the vector x. Unchanged on exit.
*
* INCX (input) const int
* On entry, INCX specifies the increment for the elements of X.
* INCX must not be zero. Unchanged on exit.
*
* ---------------------------------------------------------------------
*/
/*
* .. Local Variables ..
*/
register float absxi, scale = ATL_sZERO,
ssq = ATL_sONE, temp, x0, x1, x2, x3, x4,
x5, x6, x7;
float * StX = (float *)(X) + N * INCX;
register int i;
int n = (int)(N), nu;
const int incX2 = 2 * INCX, incX3 = 3 * INCX,
incX4 = 4 * INCX, incX5 = 5 * INCX,
incX6 = 6 * INCX, incX7 = 7 * INCX,
incX8 = 8 * INCX;
/* ..
* .. Executable Statements ..
*
*/
if( ( N < 1 ) || ( INCX < 1 ) ) return( ATL_sZERO );
else if( N == 1 ) return( Msabs( *X ) );
while( (X != StX) && ( *X == ATL_sZERO ) ) { X += INCX; n--; }
if( X == StX ) return( ATL_sZERO );
if( ( nu = ( n >> 3 ) << 3 ) != 0 )
{
StX = (float *)X + nu * INCX;
do
{
x0 = (*X); x4 = X[incX4]; x1 = X[INCX ]; x5 = X[incX5];
x2 = X[incX2]; x6 = X[incX6]; x3 = X[incX3]; x7 = X[incX7];
absxi = Msabs( x0 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x4 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x1 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x5 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x2 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x6 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x3 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
absxi = Msabs( x7 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
X += incX8;
} while( X != StX );
}
for( i = n - nu; i != 0; i-- )
{
x0 = (*X);
absxi = Msabs( x0 );
if( scale < absxi )
{
temp = scale / absxi; scale = absxi;
ssq = ATL_sONE + ssq * ( temp * temp );
}
else { temp = absxi / scale; ssq += temp * temp; }
X += INCX;
}
return( scale * (float)(sqrt( (double)(ssq) )) );
/*
* End of ATL_srefnrm2
*/
}
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