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 )

void classq(long int n, complex x, long int incx,
float ∗sscale, float ∗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 respectively. 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 vector 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 .

Sun, Inc.  —  Last change: 20 Sep 1996