?nrm2
Compute the euclidean norm of a vector.
That is, 
. X is a vector that contains n elements. ||X|| is equivalent to 
.
Interface Definition
C interface:
float cblas_snrm2 (const BLASINT N, const float *X, const BLASINT incX);
double cblas_dnrm2 (const BLASINT N, const double *X, const BLASINT incX);
float cblas_scnrm2 (const BLASINT N, const float *X, const BLASINT incX);
double cblas_dznrm2 (const BLASINT N, const double *X, const BLASINT incX);
Fortran interface:
RES = SNRM2(N, X, INCX)
RES = DNRM2(N, X, INCX)
RES = SCNRM2(N, X, INCX)
RES = DZNRM2(N, X, INCX)
Parameters
Parameter |
Type |
Description |
Input/Output |
|---|---|---|---|
N |
Integer |
Number of elements in the X vector. |
Input |
X |
|
Vector X. The vector size is at least (1+(n-1)*abs(incX)). |
Input/Output |
incX |
Integer |
Increment for the elements of vector X. |
Input |
Return Value
Vector norm. Float or double-precision floating-point type.
Dependency
#include "kblas.h"
Examples
C interface:
int n = 5, incx = 1;
float res;
/**
* X: 0.340188, -0.105617, 0.283099, 0.298440, 0.411647
*/
float x[5] = {0.340188, -0.105617, 0.283099, 0.298440, 0.411647};
res = cblas_snrm2(n, x, incx);
/**
* Output: 0.682310
*/
Fortran interface:
INTEGER :: N=5
INTEGER :: INCX=1
REAL(4) :: RES
REAL(4) :: X(5)
DATA X/0.340188, -0.105617, 0.283099, 0.298440, 0.411647/
EXTERNAL SNRM2
RES=SNRM2(N, X, INCX)
* Output : 0.682310