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nrm2(3) LAPACK nrm2(3)

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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