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Annotation of rpl/lapack/lapack/zdrscl.f, revision 1.18

1.11      bertrand    1: *> \brief \b ZDRSCL multiplies a vector by the reciprocal of a real scalar.
1.8       bertrand    2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
1.15      bertrand    5: * Online html documentation available at
                      6: *            http://www.netlib.org/lapack/explore-html/
1.8       bertrand    7: *
                      8: *> \htmlonly
1.15      bertrand    9: *> Download ZDRSCL + dependencies
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zdrscl.f">
                     11: *> [TGZ]</a>
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zdrscl.f">
                     13: *> [ZIP]</a>
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zdrscl.f">
1.8       bertrand   15: *> [TXT]</a>
1.15      bertrand   16: *> \endhtmlonly
1.8       bertrand   17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       SUBROUTINE ZDRSCL( N, SA, SX, INCX )
1.15      bertrand   22: *
1.8       bertrand   23: *       .. Scalar Arguments ..
                     24: *       INTEGER            INCX, N
                     25: *       DOUBLE PRECISION   SA
                     26: *       ..
                     27: *       .. Array Arguments ..
                     28: *       COMPLEX*16         SX( * )
                     29: *       ..
1.15      bertrand   30: *
1.8       bertrand   31: *
                     32: *> \par Purpose:
                     33: *  =============
                     34: *>
                     35: *> \verbatim
                     36: *>
                     37: *> ZDRSCL multiplies an n-element complex vector x by the real scalar
                     38: *> 1/a.  This is done without overflow or underflow as long as
                     39: *> the final result x/a does not overflow or underflow.
                     40: *> \endverbatim
                     41: *
                     42: *  Arguments:
                     43: *  ==========
                     44: *
                     45: *> \param[in] N
                     46: *> \verbatim
                     47: *>          N is INTEGER
                     48: *>          The number of components of the vector x.
                     49: *> \endverbatim
                     50: *>
                     51: *> \param[in] SA
                     52: *> \verbatim
                     53: *>          SA is DOUBLE PRECISION
                     54: *>          The scalar a which is used to divide each component of x.
                     55: *>          SA must be >= 0, or the subroutine will divide by zero.
                     56: *> \endverbatim
                     57: *>
                     58: *> \param[in,out] SX
                     59: *> \verbatim
                     60: *>          SX is COMPLEX*16 array, dimension
                     61: *>                         (1+(N-1)*abs(INCX))
                     62: *>          The n-element vector x.
                     63: *> \endverbatim
                     64: *>
                     65: *> \param[in] INCX
                     66: *> \verbatim
                     67: *>          INCX is INTEGER
                     68: *>          The increment between successive values of the vector SX.
                     69: *>          > 0:  SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i),     1< i<= n
                     70: *> \endverbatim
                     71: *
                     72: *  Authors:
                     73: *  ========
                     74: *
1.15      bertrand   75: *> \author Univ. of Tennessee
                     76: *> \author Univ. of California Berkeley
                     77: *> \author Univ. of Colorado Denver
                     78: *> \author NAG Ltd.
1.8       bertrand   79: *
                     80: *> \ingroup complex16OTHERauxiliary
                     81: *
                     82: *  =====================================================================
1.1       bertrand   83:       SUBROUTINE ZDRSCL( N, SA, SX, INCX )
                     84: *
1.18    ! bertrand   85: *  -- LAPACK auxiliary routine --
1.1       bertrand   86: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                     87: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                     88: *
                     89: *     .. Scalar Arguments ..
                     90:       INTEGER            INCX, N
                     91:       DOUBLE PRECISION   SA
                     92: *     ..
                     93: *     .. Array Arguments ..
                     94:       COMPLEX*16         SX( * )
                     95: *     ..
                     96: *
                     97: * =====================================================================
                     98: *
                     99: *     .. Parameters ..
                    100:       DOUBLE PRECISION   ZERO, ONE
                    101:       PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
                    102: *     ..
                    103: *     .. Local Scalars ..
                    104:       LOGICAL            DONE
                    105:       DOUBLE PRECISION   BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM
                    106: *     ..
                    107: *     .. External Functions ..
                    108:       DOUBLE PRECISION   DLAMCH
                    109:       EXTERNAL           DLAMCH
                    110: *     ..
                    111: *     .. External Subroutines ..
                    112:       EXTERNAL           DLABAD, ZDSCAL
                    113: *     ..
                    114: *     .. Intrinsic Functions ..
                    115:       INTRINSIC          ABS
                    116: *     ..
                    117: *     .. Executable Statements ..
                    118: *
                    119: *     Quick return if possible
                    120: *
                    121:       IF( N.LE.0 )
                    122:      $   RETURN
                    123: *
                    124: *     Get machine parameters
                    125: *
                    126:       SMLNUM = DLAMCH( 'S' )
                    127:       BIGNUM = ONE / SMLNUM
                    128:       CALL DLABAD( SMLNUM, BIGNUM )
                    129: *
                    130: *     Initialize the denominator to SA and the numerator to 1.
                    131: *
                    132:       CDEN = SA
                    133:       CNUM = ONE
                    134: *
                    135:    10 CONTINUE
                    136:       CDEN1 = CDEN*SMLNUM
                    137:       CNUM1 = CNUM / BIGNUM
                    138:       IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN
                    139: *
                    140: *        Pre-multiply X by SMLNUM if CDEN is large compared to CNUM.
                    141: *
                    142:          MUL = SMLNUM
                    143:          DONE = .FALSE.
                    144:          CDEN = CDEN1
                    145:       ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN
                    146: *
                    147: *        Pre-multiply X by BIGNUM if CDEN is small compared to CNUM.
                    148: *
                    149:          MUL = BIGNUM
                    150:          DONE = .FALSE.
                    151:          CNUM = CNUM1
                    152:       ELSE
                    153: *
                    154: *        Multiply X by CNUM / CDEN and return.
                    155: *
                    156:          MUL = CNUM / CDEN
                    157:          DONE = .TRUE.
                    158:       END IF
                    159: *
                    160: *     Scale the vector X by MUL
                    161: *
                    162:       CALL ZDSCAL( N, MUL, SX, INCX )
                    163: *
                    164:       IF( .NOT.DONE )
                    165:      $   GO TO 10
                    166: *
                    167:       RETURN
                    168: *
                    169: *     End of ZDRSCL
                    170: *
                    171:       END