C Library Functions - dnrm2 (3)

NAME

dnrm2(3f) - [BLAS:SINGLE_BLAS_LEVEL1] returns the euclidean norm of a vector via the function name

Synopsis
Definition
Options
Authors
Further Details
See Also

SYNOPSIS

double precision function dnrm2(n,x,incx)

      .. Scalar Arguments ..
      integer,intent(in) :: incx, n
      ..
      .. Array Arguments ..
      real(wp),intent(in) :: x(*)
       ..

DEFINITION

DNRM2 returns the euclidean norm of a vector via the function name, so that
    DNRM2 := sqrt( x’*x )

OPTIONS

N

number of elements in input vector(s)

X

X is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )

INCX

INCX is INTEGER, storage spacing between elements of X

           If INCX > 0, X(1+(i-1)*INCX) = x(i) for 1 <= i <= n
           If INCX < 0, X(1-(n-i)*INCX) = x(i) for 1 <= i <= n
           If INCX = 0, x isn’t a vector so there is no need to call
           this subroutine. If you call it anyway, it will count x(1)
           in the vector norm N times.

AUTHORS

o Edward Anderson, Lockheed Martin

date:August 2016

\par Contributors:

Weslley Pereira, University of Colorado Denver, USA

FURTHER DETAILS

Anderson E. (2017) Algorithm 978: Safe Scaling in the Level 1 BLAS ACM Trans Math Softw 44:1--28 https://doi.org/10.1145/3061665
Blue, James L. (1978) A Portable Fortran Program to Find the Euclidean Norm of a Vector ACM Trans Math Softw 4:15--23 https://doi.org/10.1145/355769.355771