Previous: dlasr Up: ../lapack-d.html Next: dlasv2

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( * ) PURPOSE DLASSQ returns the values scl and smsq such that 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 respec- tively. 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 The vector for which a scaled sum of squares is com- puted. x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n. INCX (input) INTEGER The increment between successive values of the vec- tor 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 scal- ing 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.