Abdelrahman Said
169 lines
4.8 KiB
C
169 lines
4.8 KiB
C
/* -- translated by f2c (version 20240504).
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You must link the resulting object file with libf2c:
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on Microsoft Windows system, link with libf2c.lib;
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm
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or, if you install libf2c.a in a standard place, with -lf2c -lm
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-- in that order, at the end of the command line, as in
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cc *.o -lf2c -lm
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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http://www.netlib.org/f2c/libf2c.zip
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*/
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#include "f2c.h"
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/* > \brief \b DLASSQ updates a sum of squares represented in scaled form.
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=========== DOCUMENTATION ===========
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Online html documentation available at
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http://www.netlib.org/lapack/explore-html/
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> \htmlonly
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> Download DLASSQ + dependencies
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlassq.
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f">
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> [TGZ]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlassq.
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f">
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> [ZIP]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlassq.
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f">
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> [TXT]</a>
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> \endhtmlonly
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Definition:
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===========
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SUBROUTINE DLASSQ( N, X, INCX, SCALE, SUMSQ )
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INTEGER INCX, N
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DOUBLE PRECISION SCALE, SUMSQ
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DOUBLE PRECISION X( * )
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> \par Purpose:
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=============
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>
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> \verbatim
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>
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> DLASSQ returns the values scl and smsq such that
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>
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> ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,
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>
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> where x( i ) = X( 1 + ( i - 1 )*INCX ). The value of sumsq is
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> assumed to be non-negative and scl returns the value
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>
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> scl = max( scale, abs( x( i ) ) ).
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>
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> scale and sumsq must be supplied in SCALE and SUMSQ and
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> scl and smsq are overwritten on SCALE and SUMSQ respectively.
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>
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> The routine makes only one pass through the vector x.
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> \endverbatim
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Arguments:
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==========
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> \param[in] N
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> \verbatim
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> N is INTEGER
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> The number of elements to be used from the vector X.
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> \endverbatim
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>
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> \param[in] X
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> \verbatim
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> X is DOUBLE PRECISION array, dimension (N)
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> The vector for which a scaled sum of squares is computed.
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> x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
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> \endverbatim
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>
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> \param[in] INCX
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> \verbatim
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> INCX is INTEGER
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> The increment between successive values of the vector X.
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> INCX > 0.
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> \endverbatim
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>
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> \param[in,out] SCALE
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> \verbatim
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> SCALE is DOUBLE PRECISION
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> On entry, the value scale in the equation above.
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> On exit, SCALE is overwritten with scl , the scaling factor
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> for the sum of squares.
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> \endverbatim
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>
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> \param[in,out] SUMSQ
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> \verbatim
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> SUMSQ is DOUBLE PRECISION
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> On entry, the value sumsq in the equation above.
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> On exit, SUMSQ is overwritten with smsq , the basic sum of
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> squares from which scl has been factored out.
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> \endverbatim
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Authors:
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========
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> \author Univ. of Tennessee
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> \author Univ. of California Berkeley
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> \author Univ. of Colorado Denver
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> \author NAG Ltd.
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> \date September 2012
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> \ingroup auxOTHERauxiliary
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=====================================================================
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Subroutine */ int igraphdlassq_(integer *n, doublereal *x, integer *incx,
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doublereal *scale, doublereal *sumsq)
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{
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/* System generated locals */
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integer i__1, i__2;
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doublereal d__1;
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/* Local variables */
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integer ix;
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doublereal absxi;
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extern logical igraphdisnan_(doublereal *);
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/* -- LAPACK auxiliary routine (version 3.4.2) --
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-- LAPACK is a software package provided by Univ. of Tennessee, --
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-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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September 2012
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=====================================================================
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Parameter adjustments */
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--x;
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/* Function Body */
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if (*n > 0) {
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i__1 = (*n - 1) * *incx + 1;
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i__2 = *incx;
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for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
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absxi = (d__1 = x[ix], abs(d__1));
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if (absxi > 0. || igraphdisnan_(&absxi)) {
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if (*scale < absxi) {
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/* Computing 2nd power */
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d__1 = *scale / absxi;
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*sumsq = *sumsq * (d__1 * d__1) + 1;
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*scale = absxi;
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} else {
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/* Computing 2nd power */
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d__1 = absxi / *scale;
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*sumsq += d__1 * d__1;
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}
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}
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/* L10: */
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}
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}
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return 0;
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/* End of DLASSQ */
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} /* igraphdlassq_ */
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