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dnrm2 examples
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DNRM2 is a BLAS level one which computes the Euclidean norm of a vector.

Given the vector [ 3.0, -4.0, 5.0, -7.0, 9.0 ]

dnrm2(3,a,1)
   = sqrt(3.0^2 + -4.0^2 + 5.0^2) 
   = sqrt(50.0)
   = 7.0710678118654755

dnrm2(5,a,1) 
   = sqrt(3.0^2 + -4.0^2 + 5.0^2 + -7.0^2 + 9.0^2) 
   = sqrt(180.0)
   = 13.416407864998739

dnrm2(3,a,2)
   = sqrt(3.0^2 + 5.0^2 + 9.0^2) 
   = sqrt(115.0)
   = 10.72380529476361

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Man Page Details
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NAME
       DNRM2 - BLAS level one, computes the Euclidean norm of a vector

SYNOPSIS
       DOUBLE PRECISION FUNCTION DNRM2 ( n, x, incx )

           INTEGER                       n, incx

           DOUBLE PRECISION              x


DESCRIPTION
       DNRM2  computes the Euclidean (L2) norm of a double precision real vec-
       tor, as follows:

               DNRM2 <-- ||x||
                              2

       where x is a double precision real vector.

ARGUMENTS
       n       INTEGER. (input)
               Number of elements in the operand vector.

       x       DOUBLE PRECISION. (input)
               Array of dimension (n-1) * |incx| + 1.
               Array x contains the operand vector.

       incx    INTEGER. (input)
               Increment between elements of x.
               If incx = 0, the results will be unpredictable.

RETURN VALUES
       DNRM2   DOUBLE PRECISION. Result (Euclidean norm). (output)
               If n <= 0, DNRM2 is set to 0d0.

NOTES
       When working backward (incx < 0), each routine starts at the end of the
       vector and moves backward, as follows:

            x(1-incx * (n-1)), x(1-incx * (n-2)), ..., x(1)

