Go to the documentation of this file.00001 #include "cs.h"
00002
00003
00004 double cs_house (double *x, double *beta, int n)
00005 {
00006 double s, sigma = 0 ;
00007 int i ;
00008 if (!x || !beta) return (-1) ;
00009 for (i = 1 ; i < n ; i++) sigma += x [i] * x [i] ;
00010 if (sigma == 0)
00011 {
00012 s = fabs (x [0]) ;
00013 (*beta) = (x [0] <= 0) ? 2 : 0 ;
00014 x [0] = 1 ;
00015 }
00016 else
00017 {
00018 s = sqrt (x [0] * x [0] + sigma) ;
00019 x [0] = (x [0] <= 0) ? (x [0] - s) : (-sigma / (x [0] + s)) ;
00020 (*beta) = -1. / (s * x [0]) ;
00021 }
00022 return (s) ;
00023 }