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zlassq.f(3) LAPACK zlassq.f(3)

zlassq.f -


subroutine zlassq (N, X, INCX, SCALE, SUMSQ)
 
ZLASSQ updates a sum of squares represented in scaled form.

ZLASSQ updates a sum of squares represented in scaled form.
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.
Parameters:
N
          N is INTEGER
          The number of elements to be used from the vector X.
X
          X is COMPLEX*16 array, dimension (N)
          The vector x as described above.
             x( i )  = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
INCX
          INCX is INTEGER
          The increment between successive values of the vector X.
          INCX > 0.
SCALE
          SCALE is DOUBLE PRECISION
          On entry, the value  scale  in the equation above.
          On exit, SCALE is overwritten with the value  scl .
SUMSQ
          SUMSQ is DOUBLE PRECISION
          On entry, the value  sumsq  in the equation above.
          On exit, SUMSQ is overwritten with the value  ssq .
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Definition at line 107 of file zlassq.f.

Generated automatically by Doxygen for LAPACK from the source code.
Sat Nov 16 2013 Version 3.4.2

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