dlassq(3S)

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

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

         INTEGER        INCX, N

         DOUBLE         PRECISION SCALE, SUMSQ

         DOUBLE         PRECISION 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
     DLASSQ 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) DOUBLE PRECISION 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) DOUBLE PRECISION
             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) DOUBLE PRECISION
             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.

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

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