DOUBLE PRECISION FUNCTION DNRM2F ( N, X, INCX )

*     .. Scalar Arguments ..

      INTEGER                           INCX, N

*     .. Array Arguments ..

      DOUBLE PRECISION                  X( * )

*     ..

*

*  DNRM2 returns the euclidean norm of a vector via the function

*  name, so that

*

*     DNRM2 := sqrt( x'*x )

*

*

*

*  -- This version written on 25-October-1982.

*     Modified on 14-October-1993 to inline the call to DLASSQ.

*     Sven Hammarling, Nag Ltd.

*

*

*     .. Parameters ..

      DOUBLE PRECISION      ONE         , ZERO

      PARAMETER           ( ONE = 1.0D+0, ZERO = 0.0D+0 )

*     .. Local Scalars ..

      INTEGER               IX

      DOUBLE PRECISION      ABSXI, NORM, SCALE, SSQ

*     .. Intrinsic Functions ..

      INTRINSIC             ABS, SQRT

*     ..

*     .. Executable Statements ..

      IF( N.LT.1 .OR. INCX.LT.1 )THEN

         NORM  = ZERO

      ELSE IF( N.EQ.1 )THEN

         NORM  = ABS( X( 1 ) )

      ELSE

         SCALE = ZERO

         SSQ   = ONE

*        The following loop is equivalent to this call to the LAPACK

*        auxiliary routine:

*        CALL DLASSQ( N, X, INCX, SCALE, SSQ )

*

         DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX

            IF( X( IX ).NE.ZERO )THEN

               ABSXI = ABS( X( IX ) )

               IF( SCALE.LT.ABSXI )THEN

                  SSQ   = ONE   + SSQ*( SCALE/ABSXI )**2

                  SCALE = ABSXI

               ELSE

                  SSQ   = SSQ   +     ( ABSXI/SCALE )**2

               END IF

            END IF

   10    CONTINUE

         NORM  = SCALE * SQRT( SSQ )

      END IF

*

      DNRM2F = NORM

      RETURN

*

*     End of DNRM2.

*

      END