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Annotation of rpl/lapack/lapack/zlassq.f, revision 1.1

1.1     ! bertrand    1:       SUBROUTINE ZLASSQ( N, X, INCX, SCALE, SUMSQ )
        !             2: *
        !             3: *  -- LAPACK auxiliary routine (version 3.2) --
        !             4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
        !             5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
        !             6: *     November 2006
        !             7: *
        !             8: *     .. Scalar Arguments ..
        !             9:       INTEGER            INCX, N
        !            10:       DOUBLE PRECISION   SCALE, SUMSQ
        !            11: *     ..
        !            12: *     .. Array Arguments ..
        !            13:       COMPLEX*16         X( * )
        !            14: *     ..
        !            15: *
        !            16: *  Purpose
        !            17: *  =======
        !            18: *
        !            19: *  ZLASSQ returns the values scl and ssq such that
        !            20: *
        !            21: *     ( scl**2 )*ssq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,
        !            22: *
        !            23: *  where x( i ) = abs( X( 1 + ( i - 1 )*INCX ) ). The value of sumsq is
        !            24: *  assumed to be at least unity and the value of ssq will then satisfy
        !            25: *
        !            26: *     1.0 .le. ssq .le. ( sumsq + 2*n ).
        !            27: *
        !            28: *  scale is assumed to be non-negative and scl returns the value
        !            29: *
        !            30: *     scl = max( scale, abs( real( x( i ) ) ), abs( aimag( x( i ) ) ) ),
        !            31: *            i
        !            32: *
        !            33: *  scale and sumsq must be supplied in SCALE and SUMSQ respectively.
        !            34: *  SCALE and SUMSQ are overwritten by scl and ssq respectively.
        !            35: *
        !            36: *  The routine makes only one pass through the vector X.
        !            37: *
        !            38: *  Arguments
        !            39: *  =========
        !            40: *
        !            41: *  N       (input) INTEGER
        !            42: *          The number of elements to be used from the vector X.
        !            43: *
        !            44: *  X       (input) COMPLEX*16 array, dimension (N)
        !            45: *          The vector x as described above.
        !            46: *             x( i )  = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
        !            47: *
        !            48: *  INCX    (input) INTEGER
        !            49: *          The increment between successive values of the vector X.
        !            50: *          INCX > 0.
        !            51: *
        !            52: *  SCALE   (input/output) DOUBLE PRECISION
        !            53: *          On entry, the value  scale  in the equation above.
        !            54: *          On exit, SCALE is overwritten with the value  scl .
        !            55: *
        !            56: *  SUMSQ   (input/output) DOUBLE PRECISION
        !            57: *          On entry, the value  sumsq  in the equation above.
        !            58: *          On exit, SUMSQ is overwritten with the value  ssq .
        !            59: *
        !            60: * =====================================================================
        !            61: *
        !            62: *     .. Parameters ..
        !            63:       DOUBLE PRECISION   ZERO
        !            64:       PARAMETER          ( ZERO = 0.0D+0 )
        !            65: *     ..
        !            66: *     .. Local Scalars ..
        !            67:       INTEGER            IX
        !            68:       DOUBLE PRECISION   TEMP1
        !            69: *     ..
        !            70: *     .. Intrinsic Functions ..
        !            71:       INTRINSIC          ABS, DBLE, DIMAG
        !            72: *     ..
        !            73: *     .. Executable Statements ..
        !            74: *
        !            75:       IF( N.GT.0 ) THEN
        !            76:          DO 10 IX = 1, 1 + ( N-1 )*INCX, INCX
        !            77:             IF( DBLE( X( IX ) ).NE.ZERO ) THEN
        !            78:                TEMP1 = ABS( DBLE( X( IX ) ) )
        !            79:                IF( SCALE.LT.TEMP1 ) THEN
        !            80:                   SUMSQ = 1 + SUMSQ*( SCALE / TEMP1 )**2
        !            81:                   SCALE = TEMP1
        !            82:                ELSE
        !            83:                   SUMSQ = SUMSQ + ( TEMP1 / SCALE )**2
        !            84:                END IF
        !            85:             END IF
        !            86:             IF( DIMAG( X( IX ) ).NE.ZERO ) THEN
        !            87:                TEMP1 = ABS( DIMAG( X( IX ) ) )
        !            88:                IF( SCALE.LT.TEMP1 ) THEN
        !            89:                   SUMSQ = 1 + SUMSQ*( SCALE / TEMP1 )**2
        !            90:                   SCALE = TEMP1
        !            91:                ELSE
        !            92:                   SUMSQ = SUMSQ + ( TEMP1 / SCALE )**2
        !            93:                END IF
        !            94:             END IF
        !            95:    10    CONTINUE
        !            96:       END IF
        !            97: *
        !            98:       RETURN
        !            99: *
        !           100: *     End of ZLASSQ
        !           101: *
        !           102:       END