1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
#include "cs.h"
/* apply the ith Householder vector to x */
int cs_happly (const cs *V, int i, double beta, double *x)
{
int p, *Vp, *Vi ;
double *Vx, tau = 0 ;
if (!CS_CSC (V) || !x) return (0) ; /* check inputs */
Vp = V->p ; Vi = V->i ; Vx = V->x ;
for (p = Vp [i] ; p < Vp [i+1] ; p++) /* tau = v'*x */
{
tau += Vx [p] * x [Vi [p]] ;
}
tau *= beta ; /* tau = beta*(v'*x) */
for (p = Vp [i] ; p < Vp [i+1] ; p++) /* x = x - v*tau */
{
x [Vi [p]] -= Vx [p] * tau ;
}
return (1) ;
}
|
