- SUBROUTINE SLASSQ(
- N, X, INCX, SCALE, SUMSQ )
- INTEGER INCX, N
- REAL SCALE, SUMSQ
- REAL X( * )
PURPOSESLASSQ 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 respectively. The routine makes only one pass through the vector x.
- N (input) INTEGER
- The number of elements to be used from the vector X.
- X (input) REAL 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) REAL
- 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) REAL
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.