?lassq

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

Download PDF

ID 766686

Date 12/16/2022

Version

Public

A newer version of this document is available. Customers should click here to go to the newest version.

Visible to Intel only — GUID: GUID-7E687245-60A6-49EE-B989-4A37C8C20599

View Details

?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.

Parent topic: LAPACK Auxiliary Routines

Select Your Language

Using Intel.com Search

Quick Links

Recent Searches

Advanced Search

Only search in

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

?lassq