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

1.1     ! bertrand    1:       SUBROUTINE ZDRSCL( N, SA, SX, INCX )
        !             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   SA
        !            11: *     ..
        !            12: *     .. Array Arguments ..
        !            13:       COMPLEX*16         SX( * )
        !            14: *     ..
        !            15: *
        !            16: *  Purpose
        !            17: *  =======
        !            18: *
        !            19: *  ZDRSCL multiplies an n-element complex vector x by the real scalar
        !            20: *  1/a.  This is done without overflow or underflow as long as
        !            21: *  the final result x/a does not overflow or underflow.
        !            22: *
        !            23: *  Arguments
        !            24: *  =========
        !            25: *
        !            26: *  N       (input) INTEGER
        !            27: *          The number of components of the vector x.
        !            28: *
        !            29: *  SA      (input) DOUBLE PRECISION
        !            30: *          The scalar a which is used to divide each component of x.
        !            31: *          SA must be >= 0, or the subroutine will divide by zero.
        !            32: *
        !            33: *  SX      (input/output) COMPLEX*16 array, dimension
        !            34: *                         (1+(N-1)*abs(INCX))
        !            35: *          The n-element vector x.
        !            36: *
        !            37: *  INCX    (input) INTEGER
        !            38: *          The increment between successive values of the vector SX.
        !            39: *          > 0:  SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i),     1< i<= n
        !            40: *
        !            41: * =====================================================================
        !            42: *
        !            43: *     .. Parameters ..
        !            44:       DOUBLE PRECISION   ZERO, ONE
        !            45:       PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
        !            46: *     ..
        !            47: *     .. Local Scalars ..
        !            48:       LOGICAL            DONE
        !            49:       DOUBLE PRECISION   BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM
        !            50: *     ..
        !            51: *     .. External Functions ..
        !            52:       DOUBLE PRECISION   DLAMCH
        !            53:       EXTERNAL           DLAMCH
        !            54: *     ..
        !            55: *     .. External Subroutines ..
        !            56:       EXTERNAL           DLABAD, ZDSCAL
        !            57: *     ..
        !            58: *     .. Intrinsic Functions ..
        !            59:       INTRINSIC          ABS
        !            60: *     ..
        !            61: *     .. Executable Statements ..
        !            62: *
        !            63: *     Quick return if possible
        !            64: *
        !            65:       IF( N.LE.0 )
        !            66:      $   RETURN
        !            67: *
        !            68: *     Get machine parameters
        !            69: *
        !            70:       SMLNUM = DLAMCH( 'S' )
        !            71:       BIGNUM = ONE / SMLNUM
        !            72:       CALL DLABAD( SMLNUM, BIGNUM )
        !            73: *
        !            74: *     Initialize the denominator to SA and the numerator to 1.
        !            75: *
        !            76:       CDEN = SA
        !            77:       CNUM = ONE
        !            78: *
        !            79:    10 CONTINUE
        !            80:       CDEN1 = CDEN*SMLNUM
        !            81:       CNUM1 = CNUM / BIGNUM
        !            82:       IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN
        !            83: *
        !            84: *        Pre-multiply X by SMLNUM if CDEN is large compared to CNUM.
        !            85: *
        !            86:          MUL = SMLNUM
        !            87:          DONE = .FALSE.
        !            88:          CDEN = CDEN1
        !            89:       ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN
        !            90: *
        !            91: *        Pre-multiply X by BIGNUM if CDEN is small compared to CNUM.
        !            92: *
        !            93:          MUL = BIGNUM
        !            94:          DONE = .FALSE.
        !            95:          CNUM = CNUM1
        !            96:       ELSE
        !            97: *
        !            98: *        Multiply X by CNUM / CDEN and return.
        !            99: *
        !           100:          MUL = CNUM / CDEN
        !           101:          DONE = .TRUE.
        !           102:       END IF
        !           103: *
        !           104: *     Scale the vector X by MUL
        !           105: *
        !           106:       CALL ZDSCAL( N, MUL, SX, INCX )
        !           107: *
        !           108:       IF( .NOT.DONE )
        !           109:      $   GO TO 10
        !           110: *
        !           111:       RETURN
        !           112: *
        !           113: *     End of ZDRSCL
        !           114: *
        !           115:       END