OpenBLAS/reference/dznrm2f.f

      DOUBLE PRECISION FUNCTION DZNRM2F( N, X, INCX )
*     .. Scalar Arguments ..
      INTEGER                           INCX, N
*     .. Array Arguments ..
      COMPLEX*16                        X( * )
*     ..
*
*  DZNRM2 returns the euclidean norm of a vector via the function
*  name, so that
*
*     DZNRM2 := sqrt( conjg( x' )*x )
*
*
*
*  -- This version written on 25-October-1982.
*     Modified on 14-October-1993 to inline the call to ZLASSQ.
*     Sven Hammarling, Nag Ltd.
*
*
*     .. Parameters ..
      DOUBLE PRECISION      ONE         , ZERO
      PARAMETER           ( ONE = 1.0D+0, ZERO = 0.0D+0 )
*     .. Local Scalars ..
      INTEGER               IX
      DOUBLE PRECISION      NORM, SCALE, SSQ, TEMP
*     .. Intrinsic Functions ..
      INTRINSIC             ABS, DIMAG, DBLE, SQRT
*     ..
*     .. Executable Statements ..
      IF( N.LT.1 .OR. INCX.LT.1 )THEN
         NORM  = ZERO
      ELSE
         SCALE = ZERO
         SSQ   = ONE
*        The following loop is equivalent to this call to the LAPACK
*        auxiliary routine:
*        CALL ZLASSQ( N, X, INCX, SCALE, SSQ )
*
         DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX
            IF( DBLE( X( IX ) ).NE.ZERO )THEN
               TEMP = ABS( DBLE( X( IX ) ) )
               IF( SCALE.LT.TEMP )THEN
                  SSQ   = ONE   + SSQ*( SCALE/TEMP )**2
                  SCALE = TEMP
               ELSE
                  SSQ   = SSQ   +     ( TEMP/SCALE )**2
               END IF
            END IF
            IF( DIMAG( X( IX ) ).NE.ZERO )THEN
               TEMP = ABS( DIMAG( X( IX ) ) )
               IF( SCALE.LT.TEMP )THEN
                  SSQ   = ONE   + SSQ*( SCALE/TEMP )**2
                  SCALE = TEMP
               ELSE
                  SSQ   = SSQ   +     ( TEMP/SCALE )**2
               END IF
            END IF
   10    CONTINUE
         NORM  = SCALE * SQRT( SSQ )
      END IF
*
      DZNRM2F = NORM
      RETURN
*
*     End of DZNRM2.
*
      END