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1 SUBROUTINE ZDRSCL( N, SA, SX, INCX ) |
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2 * |
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3 * -- LAPACK auxiliary routine (version 3.0) -- |
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2329
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4 * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., |
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5 * Courant Institute, Argonne National Lab, and Rice University |
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6 * September 30, 1994 |
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7 * |
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8 * .. Scalar Arguments .. |
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9 INTEGER INCX, N |
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10 DOUBLE PRECISION SA |
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11 * .. |
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12 * .. Array Arguments .. |
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13 COMPLEX*16 SX( * ) |
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14 * .. |
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15 * |
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16 * Purpose |
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17 * ======= |
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18 * |
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19 * ZDRSCL multiplies an n-element complex vector x by the real scalar |
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20 * 1/a. This is done without overflow or underflow as long as |
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21 * the final result x/a does not overflow or underflow. |
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22 * |
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23 * Arguments |
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24 * ========= |
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25 * |
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26 * N (input) INTEGER |
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27 * The number of components of the vector x. |
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28 * |
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29 * SA (input) DOUBLE PRECISION |
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30 * The scalar a which is used to divide each component of x. |
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31 * SA must be >= 0, or the subroutine will divide by zero. |
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32 * |
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33 * SX (input/output) COMPLEX*16 array, dimension |
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34 * (1+(N-1)*abs(INCX)) |
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35 * The n-element vector x. |
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36 * |
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37 * INCX (input) INTEGER |
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38 * The increment between successive values of the vector SX. |
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39 * > 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n |
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40 * |
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41 * ===================================================================== |
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42 * |
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43 * .. Parameters .. |
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44 DOUBLE PRECISION ZERO, ONE |
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45 PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 ) |
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46 * .. |
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47 * .. Local Scalars .. |
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48 LOGICAL DONE |
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49 DOUBLE PRECISION BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM |
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50 * .. |
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51 * .. External Functions .. |
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52 DOUBLE PRECISION DLAMCH |
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53 EXTERNAL DLAMCH |
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54 * .. |
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55 * .. External Subroutines .. |
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56 EXTERNAL DLABAD, ZDSCAL |
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57 * .. |
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58 * .. Intrinsic Functions .. |
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59 INTRINSIC ABS |
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60 * .. |
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61 * .. Executable Statements .. |
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62 * |
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63 * Quick return if possible |
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64 * |
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65 IF( N.LE.0 ) |
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66 $ RETURN |
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67 * |
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68 * Get machine parameters |
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69 * |
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70 SMLNUM = DLAMCH( 'S' ) |
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71 BIGNUM = ONE / SMLNUM |
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72 CALL DLABAD( SMLNUM, BIGNUM ) |
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73 * |
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74 * Initialize the denominator to SA and the numerator to 1. |
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75 * |
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76 CDEN = SA |
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77 CNUM = ONE |
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78 * |
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79 10 CONTINUE |
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80 CDEN1 = CDEN*SMLNUM |
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81 CNUM1 = CNUM / BIGNUM |
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82 IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN |
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83 * |
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84 * Pre-multiply X by SMLNUM if CDEN is large compared to CNUM. |
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85 * |
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86 MUL = SMLNUM |
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87 DONE = .FALSE. |
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88 CDEN = CDEN1 |
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89 ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN |
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90 * |
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91 * Pre-multiply X by BIGNUM if CDEN is small compared to CNUM. |
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92 * |
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93 MUL = BIGNUM |
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94 DONE = .FALSE. |
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95 CNUM = CNUM1 |
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96 ELSE |
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97 * |
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98 * Multiply X by CNUM / CDEN and return. |
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99 * |
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100 MUL = CNUM / CDEN |
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101 DONE = .TRUE. |
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102 END IF |
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103 * |
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104 * Scale the vector X by MUL |
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105 * |
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106 CALL ZDSCAL( N, MUL, SX, INCX ) |
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107 * |
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108 IF( .NOT.DONE ) |
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109 $ GO TO 10 |
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110 * |
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111 RETURN |
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112 * |
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113 * End of ZDRSCL |
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114 * |
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115 END |
