nrm2(3) Library Functions Manual nrm2(3)

nrm2 - nrm2: || x ||_2


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

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

Definition at line 88 of file dnrm2.f90.

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

Definition at line 89 of file dznrm2.f90.

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

Definition at line 89 of file scnrm2.f90.

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

Definition at line 88 of file snrm2.f90.

Generated automatically by Doxygen for LAPACK from the source code.

Version 3.12.0 LAPACK