---
name: "classq"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/classq/3lapack"
---

# classq(3lapack)

returns the values scl and ssq such that ( scl\*\*2 )\*ssq = x( 1 )\*\*2 +...+ x( n )\*\*2 + ( scale\*\*2 )\*sumsq,

## NAME

CLASSQ - returns 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 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) COMPLEX array, dimension (N)

  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 .