104 lines
2.7 KiB
C
104 lines
2.7 KiB
C
|
#include "clapack.h"
|
||
|
|
|
||
|
|
/* Subroutine */ int slassq_(integer *n, real *x, integer *incx, real *scale,
|
||
|
|
real *sumsq)
|
||
|
|
{
|
||
|
|
/* System generated locals */
|
||
|
|
integer i__1, i__2;
|
||
|
|
real r__1;
|
||
|
|
|
||
|
|
/* Local variables */
|
||
|
|
integer ix;
|
||
|
|
real absxi;
|
||
|
|
|
||
|
|
|
||
|
|
/* -- LAPACK auxiliary routine (version 3.1) -- */
|
||
|
|
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
|
||
|
|
/* November 2006 */
|
||
|
|
|
||
|
|
/* .. Scalar Arguments .. */
|
||
|
|
/* .. */
|
||
|
|
/* .. Array Arguments .. */
|
||
|
|
/* .. */
|
||
|
|
|
||
|
|
/* Purpose */
|
||
|
|
/* ======= */
|
||
|
|
|
||
|
|
/* SLASSQ returns the values scl and smsq such that */
|
||
|
|
|
||
|
|
/* ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq, */
|
||
|
|
|
||
|
|
/* where x( i ) = X( 1 + ( i - 1 )*INCX ). The value of sumsq is */
|
||
|
|
/* assumed to be non-negative and scl returns the value */
|
||
|
|
|
||
|
|
/* scl = max( scale, abs( x( i ) ) ). */
|
||
|
|
|
||
|
|
/* scale and sumsq must be supplied in SCALE and SUMSQ and */
|
||
|
|
/* scl and smsq are overwritten on SCALE and SUMSQ respectively. */
|
||
|
|
|
||
|
|
/* The routine makes only one pass through the vector x. */
|
||
|
|
|
||
|
|
/* Arguments */
|
||
|
|
/* ========= */
|
||
|
|
|
||
|
|
/* N (input) INTEGER */
|
||
|
|
/* The number of elements to be used from the vector X. */
|
||
|
|
|
||
|
|
/* X (input) REAL array, dimension (N) */
|
||
|
|
/* The vector for which a scaled sum of squares is computed. */
|
||
|
|
/* x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n. */
|
||
|
|
|
||
|
|
/* INCX (input) INTEGER */
|
||
|
|
/* The increment between successive values of the vector X. */
|
||
|
|
/* INCX > 0. */
|
||
|
|
|
||
|
|
/* SCALE (input/output) REAL */
|
||
|
|
/* On entry, the value scale in the equation above. */
|
||
|
|
/* On exit, SCALE is overwritten with scl , the scaling factor */
|
||
|
|
/* for the sum of squares. */
|
||
|
|
|
||
|
|
/* SUMSQ (input/output) REAL */
|
||
|
|
/* On entry, the value sumsq in the equation above. */
|
||
|
|
/* On exit, SUMSQ is overwritten with smsq , the basic sum of */
|
||
|
|
/* squares from which scl has been factored out. */
|
||
|
|
|
||
|
|
/* ===================================================================== */
|
||
|
|
|
||
|
|
/* .. Parameters .. */
|
||
|
|
/* .. */
|
||
|
|
/* .. Local Scalars .. */
|
||
|
|
/* .. */
|
||
|
|
/* .. Intrinsic Functions .. */
|
||
|
|
/* .. */
|
||
|
|
/* .. Executable Statements .. */
|
||
|
|
|
||
|
|
/* Parameter adjustments */
|
||
|
|
--x;
|
||
|
|
|
||
|
|
/* Function Body */
|
||
|
|
if (*n > 0) {
|
||
|
|
i__1 = (*n - 1) * *incx + 1;
|
||
|
|
i__2 = *incx;
|
||
|
|
for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
|
||
|
|
if (x[ix] != 0.f) {
|
||
|
|
absxi = (r__1 = x[ix], dabs(r__1));
|
||
|
|
if (*scale < absxi) {
|
||
|
|
/* Computing 2nd power */
|
||
|
|
r__1 = *scale / absxi;
|
||
|
|
*sumsq = *sumsq * (r__1 * r__1) + 1;
|
||
|
|
*scale = absxi;
|
||
|
|
} else {
|
||
|
|
/* Computing 2nd power */
|
||
|
|
r__1 = absxi / *scale;
|
||
|
|
*sumsq += r__1 * r__1;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
/* L10: */
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
/* End of SLASSQ */
|
||
|
|
|
||
|
|
} /* slassq_ */
|