Provided by: liblapack-doc_3.12.1-2_all 
NAME
nrm2 - nrm2: || x ||_2
SYNOPSIS
Functions
real(wp) function dnrm2 (n, x, incx)
DNRM2
real(wp) function dznrm2 (n, x, incx)
DZNRM2
real(wp) function scnrm2 (n, x, incx)
SCNRM2
real(wp) function snrm2 (n, x, incx)
SNRM2
Detailed Description
Function Documentation
real(wp) function dnrm2 (integer n, real(wp), dimension(*) x, integer incx)
DNRM2
Purpose:
DNRM2 returns the euclidean norm of a vector via the function
name, so that
DNRM2 := sqrt( x'*x )
Parameters
N
N is INTEGER
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.
Author
Edward Anderson, Lockheed Martin
Date
August 2016
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
real(wp) function dznrm2 (integer n, complex(wp), dimension(*) x, integer incx)
DZNRM2
Purpose:
DZNRM2 returns the euclidean norm of a vector via the function
name, so that
DZNRM2 := sqrt( x**H*x )
Parameters
N
N is INTEGER
number of elements in input vector(s)
X
X is COMPLEX*16 array, dimension (N)
complex vector with N elements
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.
Author
Edward Anderson, Lockheed Martin
Date
August 2016
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
real(wp) function scnrm2 (integer n, complex(wp), dimension(*) x, integer incx)
SCNRM2
Purpose:
SCNRM2 returns the euclidean norm of a vector via the function
name, so that
SCNRM2 := sqrt( x**H*x )
Parameters
N
N is INTEGER
number of elements in input vector(s)
X
X is COMPLEX array, dimension (N)
complex vector with N elements
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.
Author
Edward Anderson, Lockheed Martin
Date
August 2016
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
real(wp) function snrm2 (integer n, real(wp), dimension(*) x, integer incx)
SNRM2
Purpose:
SNRM2 returns the euclidean norm of a vector via the function
name, so that
SNRM2 := sqrt( x'*x ).
Parameters
N
N is INTEGER
number of elements in input vector(s)
X
X is REAL 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.
Author
Edward Anderson, Lockheed Martin
Date
August 2016
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
Author
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Version 3.12.0 Tue Jan 28 2025 00:54:31 nrm2(3)