zlassq(3S)

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

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

         INTEGER        INCX, N

         DOUBLE         PRECISION SCALE, SUMSQ

         COMPLEX*16     X( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

PURPOSE
     ZLASSQ returns the values scl and ssq such that ( scl**2 )*ssq = x( 1
     )**2 +...+ x( n )**2 + ( scale**2 )*sumsq, 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*16 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) DOUBLE PRECISION
             On entry, the value  scale  in the equation above.  On exit,
             SCALE is overwritten with the value  scl .

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

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

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