snrm2(3S)

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

SYNOPSIS
     Single precision

          Fortran:
               real SNRM2
               real enrm
               enrm = SNRM2 (n, x, incx)

          C/C++:
               #include <scsl_blas.h>
               float snrm2 (int n, float *x, int incx);

     Double precision

          Fortran:
               double precision DNRM2
               double precision enrm
               enrm = DNRM2 (n, xi, incx)

          C/C++:
               #include <scsl_blas.h>
               double dnrm2 (int n, double *x, int incx);

     Single precision complex

          Fortran:
               real SCNRM2
               real enrm
               enrm = SCNRM2 (n, x, incx)

          C/C++:
               #include <scsl_blas.h>
               float scnrm2 (int n, scsl_complex *x, int incx);

          C++ STL:
               #include <complex.h>
               #include <scsl_blas.h>
               float scnrm2 (int n, complex<float> *x, int incx);

     Double precision complex

          Fortran:
               double precision DZNRM2
               double precision enrm
               enrm = DZNRM2 (n, xi, incx)

          C/C++:
               #include <scsl_blas.h>
               double dznrm2 (int n, scsl_zomplex *x, int incx);
          C++ STL:
               #include <complex.h>
               #include <scsl_blas.h>
               double dznrm2 (int n, complex<double> *x, int incx);

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

     The C and C++ prototypes shown above are appropriate for the 4-byte
     integer version of SCSL. When using the 8-byte integer version, the
     variables of type int become long long and the <scsl_blas_i8.h> header
     file should be included.

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

          enrm <- ||x||   =
                       2

                 T            n      2
          sqrt (x x) = sqrt (Sum * x  )
                             i=1    i



     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
                 H            n  _
          sqrt (x x) = sqrt (Sum x x )
                             i=1  i i


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

     See the NOTES section of this man page for information about the
     interpretation of the data types described in the following arguments.

     These functions have the following arguments:

     enrm      Result.  (output)
               SNRM2: Single precision result.
               DNRM2: Double precision result.
               SCNRM2: Single precision complex result.
               DZNRM2:  Double precision complex 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: Single precision array.
               DNRM2: Double precision array.
               SCNRM2: Single precision complex array.
               DZNRM2:  Double precision 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)


   Data Types
     The following data types are described in this documentation:

          Term Used                     Data type

     Fortran:

          Array dimensioned n           x(n)

          Integer                       INTEGER (INTEGER*8 for -lscs_i8[_mp])

          Single precision              REAL

          Double precision              DOUBLE PRECISION

          Single precision complex      COMPLEX

          Double precision complex      DOUBLE COMPLEX

     C/C++:

          Array dimensioned n           x[n]

          Integer                       int (long long for -lscs_i8[_mp])

          Single precision              float

          Double precision              double

          Single precision complex      scsl_complex

          Double precision complex      scsl_zomplex

     C++ STL:

          Array dimensioned n           x[n]

          Integer                       int (long long for -lscs_i8[_mp])

          Single precision              float

          Double precision              double

          Single precision complex      complex<float>

          Double precision complex      complex<double>

SEE ALSO
     INTRO_SCSL(3S), INTRO_BLAS1(3S)

     INTRO_CBLAS(3S) for information about using the C interface to Fortran 77
     Basic Linear Algebra Subprograms (legacy BLAS) set forth by the Basic
     Linear Algebra Subprograms Technical Forum.