Previous: clasr Up: ../lapack-c.html Next: claswp

# classq

```
NAME
CLASSQ - return the values scl and ssq such that   ( scl**2
)*ssq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,

SYNOPSIS
SUBROUTINE CLASSQ( N, X, INCX, SCALE, SUMSQ )

INTEGER        INCX, N

REAL           SCALE, SUMSQ

COMPLEX        X( * )

PURPOSE
CLASSQ returns the values scl and ssq such that

where x( i ) = abs( X( 1 + ( i - 1 )*INCX ) ). The value of
sumsq is assumed to be at least unity and the value of ssq
will then satisfy

1.0 .le. ssq .le. ( sumsq + 2*n ).

scale is assumed to be non-negative and scl returns the
value

scl = max( scale, abs( real( x( i ) ) ), abs( aimag( x( i
) ) ) ),
i

scale and sumsq must be supplied in SCALE and SUMSQ respec-
tively.  SCALE and SUMSQ are overwritten by scl and ssq
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
The vector x as described above.  x( i )  = X( 1 + (
i - 1 )*INCX ), 1 <= i <= n.

INCX    (input) INTEGER
The increment between successive values of the vec-
tor X.  INCX > 0.

SCALE   (input/output) REAL
On entry, the value  scale  in the equation above.
On exit, SCALE is overwritten with the value  scl .

SUMSQ   (input/output) REAL
On entry, the value  sumsq  in the equation above.
On exit, SUMSQ is overwritten with the value  ssq .
```