nrm2(3F)

NAME
     SNRM2, DNRM2, SCNRM2, DZNRM2 - Computes the Euclidean norm of a vector

SYNOPSIS
     Real

        enrm = SNRM2 (n, x, incx)

     Double precision

        enrm = DNRM2 (n, xi, incx)

     Complex

        enrm = SCNRM2 (n, x, incx)

     Double complex

        enrm = DZNRM2 (n, xi, incx)

DESCRIPTION
     SNRM2/DNRM2 computes the Euclidean (l2) norm of a real vector, as
     follows:

          enrm <- ||x||2 =

                              n
          sqrt (xTx) = sqrt (Sum * xi2)
                             i=1


     where x is a real vector, and xT denotes the transpose of x.

     SCNRM2/DZNRM2 computes the Euclidean (l2) norm of a complex vector, as
     follows:

          enrm <- ||x||2 =

                              n  _
          sqrt (xHx) = sqrt (Sum xixi)
                             i=1

     where x is a complex vector, and xH denotes the conjugate transpose of
     x.

     These functions have the following arguments:

     enrm      Result.  (output)
               SNRM2: Real result.
               DNRM2: Double precision result.
               SCNRM2: Real result.
               DZNRM2:  Double precision result.
               Result (Euclidean norm).  If n <= 0, enrm is set to 0.

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

     x         Array of dimension (n-1) * |incx| + 1.  (input)
               SNRM2: Real array.
               DNRM2: Double precision array.
               SCNRM2: Complex array.
               DZNRM2:  Double complex array.
               Array x contains the operand vector.

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

NOTES
     These routines are Level 1 Basic Linear Algebra Subprograms (Level 1
     BLAS).

     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)