OpenBLAS/reference/scnrm2f.f

      REAL             FUNCTION SCNRM2F( N, X, INCX )
*     .. Scalar Arguments ..
      INTEGER                           INCX, N
*     .. Array Arguments ..
      COMPLEX                           X( * )
*     ..
*
*  SCNRM2 returns the euclidean norm of a vector via the function
*  name, so that
*
*     SCNRM2 := sqrt( conjg( x' )*x )
*
*
*
*  -- This version written on 25-October-1982.
*     Modified on 14-October-1993 to inline the call to CLASSQ.
*     Sven Hammarling, Nag Ltd.
*
*
*     .. Parameters ..
      REAL                  ONE         , ZERO
      PARAMETER           ( ONE = 1.0E+0, ZERO = 0.0E+0 )
*     .. Local Scalars ..
      INTEGER               IX
      REAL                  NORM, SCALE, SSQ, TEMP
*     .. Intrinsic Functions ..
      INTRINSIC             ABS, AIMAG, REAL, 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 CLASSQ( N, X, INCX, SCALE, SSQ )
*
         DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX
            IF( REAL( X( IX ) ).NE.ZERO )THEN
               TEMP = ABS( REAL( 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( AIMAG( X( IX ) ).NE.ZERO )THEN
               TEMP = ABS( AIMAG( 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
*
      SCNRM2F = NORM
      RETURN
*
*     End of SCNRM2.
*
      END