Visible to Intel only — GUID: GUID-7E687245-60A6-49EE-B989-4A37C8C20599
Visible to Intel only — GUID: GUID-7E687245-60A6-49EE-B989-4A37C8C20599
?lassq
Updates a sum of squares represented in scaled form.
Syntax
call slassq( n, x, incx, scale, sumsq )
call dlassq( n, x, incx, scale, sumsq )
call classq( n, x, incx, scale, sumsq )
call zlassq( n, x, incx, scale, sumsq )
Include Files
- mkl.fi
Description
The real routines slassq/dlassq return the values scl and smsq such that
scl2 * smsq = x(1)2 +...+ x(n)2 + scale2 *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))).
Values scale and sumsq must be supplied in scale and sumsq, and scl and smsq are overwritten on scale and sumsq, respectively.
The complex routines classq/zlassq return the values scl and ssq such that
scl2 * ssq = x(1)2 +...+ x(n)2 + scale2 *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 ≤ ssq ≤ sumsq + 2n
scale is assumed to be non-negative and scl returns the value
scl = max( scale, abs(real(x(i))), abs(aimag(x(i)))).
Values scale and sumsq must be supplied in scale and sumsq, and scl and ssq are overwritten on scale and sumsq, respectively.
All routines ?lassq make only one pass through the vector x.
Input Parameters
- n
-
INTEGER. The number of elements to be used from the vector x.
- x
-
REAL for slassq
DOUBLE PRECISION for dlassq
COMPLEX for classq
DOUBLE COMPLEX for zlassq.
The vector for which a scaled sum of squares is computed: x(i) = x(1+(i-1)*incx), 1 ≤ i ≤ n.
- incx
-
INTEGER. The increment between successive values of the vector x. incx > 0.
- scale
-
REAL for slassq/classq
DOUBLE PRECISION for dlassq/zlassq.
On entry, the value scale in the equation above.
- sumsq
-
REAL for slassq/classq
DOUBLE PRECISION for dlassq/zlassq.
On entry, the value sumsq in the equation above.
Output Parameters
- scale
-
On exit, scale is overwritten with scl, the scaling factor for the sum of squares.
- sumsq
-
For real flavors:
On exit, sumsq is overwritten with the value smsq in the equation above.
For complex flavors:
On exit, sumsq is overwritten with the value ssq in the equation above.