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2329
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1 SUBROUTINE DLASRT( ID, N, D, INFO ) |
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2 * |
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3 * -- LAPACK 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 CHARACTER ID |
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10 INTEGER INFO, N |
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11 * .. |
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12 * .. Array Arguments .. |
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13 DOUBLE PRECISION D( * ) |
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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 * Sort the numbers in D in increasing order (if ID = 'I') or |
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20 * in decreasing order (if ID = 'D' ). |
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21 * |
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22 * Use Quick Sort, reverting to Insertion sort on arrays of |
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23 * size <= 20. Dimension of STACK limits N to about 2**32. |
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24 * |
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25 * Arguments |
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26 * ========= |
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27 * |
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28 * ID (input) CHARACTER*1 |
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29 * = 'I': sort D in increasing order; |
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30 * = 'D': sort D in decreasing order. |
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31 * |
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32 * N (input) INTEGER |
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33 * The length of the array D. |
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34 * |
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35 * D (input/output) DOUBLE PRECISION array, dimension (N) |
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36 * On entry, the array to be sorted. |
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37 * On exit, D has been sorted into increasing order |
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38 * (D(1) <= ... <= D(N) ) or into decreasing order |
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39 * (D(1) >= ... >= D(N) ), depending on ID. |
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40 * |
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41 * INFO (output) INTEGER |
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42 * = 0: successful exit |
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43 * < 0: if INFO = -i, the i-th argument had an illegal value |
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44 * |
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45 * ===================================================================== |
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46 * |
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47 * .. Parameters .. |
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48 INTEGER SELECT |
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49 PARAMETER ( SELECT = 20 ) |
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50 * .. |
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51 * .. Local Scalars .. |
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52 INTEGER DIR, ENDD, I, J, START, STKPNT |
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53 DOUBLE PRECISION D1, D2, D3, DMNMX, TMP |
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54 * .. |
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55 * .. Local Arrays .. |
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56 INTEGER STACK( 2, 32 ) |
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57 * .. |
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58 * .. External Functions .. |
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59 LOGICAL LSAME |
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60 EXTERNAL LSAME |
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61 * .. |
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62 * .. External Subroutines .. |
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63 EXTERNAL XERBLA |
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64 * .. |
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65 * .. Executable Statements .. |
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66 * |
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67 * Test the input paramters. |
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68 * |
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69 INFO = 0 |
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70 DIR = -1 |
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71 IF( LSAME( ID, 'D' ) ) THEN |
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72 DIR = 0 |
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73 ELSE IF( LSAME( ID, 'I' ) ) THEN |
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74 DIR = 1 |
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75 END IF |
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76 IF( DIR.EQ.-1 ) THEN |
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77 INFO = -1 |
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78 ELSE IF( N.LT.0 ) THEN |
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79 INFO = -2 |
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80 END IF |
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81 IF( INFO.NE.0 ) THEN |
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82 CALL XERBLA( 'DLASRT', -INFO ) |
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83 RETURN |
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84 END IF |
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85 * |
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86 * Quick return if possible |
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87 * |
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88 IF( N.LE.1 ) |
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89 $ RETURN |
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90 * |
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91 STKPNT = 1 |
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92 STACK( 1, 1 ) = 1 |
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93 STACK( 2, 1 ) = N |
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94 10 CONTINUE |
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95 START = STACK( 1, STKPNT ) |
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96 ENDD = STACK( 2, STKPNT ) |
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97 STKPNT = STKPNT - 1 |
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98 IF( ENDD-START.LE.SELECT .AND. ENDD-START.GT.0 ) THEN |
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99 * |
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100 * Do Insertion sort on D( START:ENDD ) |
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101 * |
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102 IF( DIR.EQ.0 ) THEN |
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103 * |
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104 * Sort into decreasing order |
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105 * |
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106 DO 30 I = START + 1, ENDD |
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107 DO 20 J = I, START + 1, -1 |
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108 IF( D( J ).GT.D( J-1 ) ) THEN |
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109 DMNMX = D( J ) |
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110 D( J ) = D( J-1 ) |
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111 D( J-1 ) = DMNMX |
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112 ELSE |
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113 GO TO 30 |
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114 END IF |
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115 20 CONTINUE |
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116 30 CONTINUE |
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117 * |
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118 ELSE |
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119 * |
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120 * Sort into increasing order |
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121 * |
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122 DO 50 I = START + 1, ENDD |
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123 DO 40 J = I, START + 1, -1 |
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124 IF( D( J ).LT.D( J-1 ) ) THEN |
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125 DMNMX = D( J ) |
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126 D( J ) = D( J-1 ) |
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127 D( J-1 ) = DMNMX |
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128 ELSE |
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129 GO TO 50 |
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130 END IF |
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131 40 CONTINUE |
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132 50 CONTINUE |
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133 * |
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134 END IF |
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135 * |
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136 ELSE IF( ENDD-START.GT.SELECT ) THEN |
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137 * |
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138 * Partition D( START:ENDD ) and stack parts, largest one first |
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139 * |
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140 * Choose partition entry as median of 3 |
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141 * |
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142 D1 = D( START ) |
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143 D2 = D( ENDD ) |
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144 I = ( START+ENDD ) / 2 |
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145 D3 = D( I ) |
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146 IF( D1.LT.D2 ) THEN |
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147 IF( D3.LT.D1 ) THEN |
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148 DMNMX = D1 |
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149 ELSE IF( D3.LT.D2 ) THEN |
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150 DMNMX = D3 |
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151 ELSE |
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152 DMNMX = D2 |
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153 END IF |
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154 ELSE |
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155 IF( D3.LT.D2 ) THEN |
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156 DMNMX = D2 |
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157 ELSE IF( D3.LT.D1 ) THEN |
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158 DMNMX = D3 |
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159 ELSE |
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160 DMNMX = D1 |
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161 END IF |
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162 END IF |
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163 * |
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164 IF( DIR.EQ.0 ) THEN |
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165 * |
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166 * Sort into decreasing order |
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167 * |
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168 I = START - 1 |
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169 J = ENDD + 1 |
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170 60 CONTINUE |
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171 70 CONTINUE |
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172 J = J - 1 |
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173 IF( D( J ).LT.DMNMX ) |
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174 $ GO TO 70 |
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175 80 CONTINUE |
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176 I = I + 1 |
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177 IF( D( I ).GT.DMNMX ) |
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178 $ GO TO 80 |
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179 IF( I.LT.J ) THEN |
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180 TMP = D( I ) |
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181 D( I ) = D( J ) |
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182 D( J ) = TMP |
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183 GO TO 60 |
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184 END IF |
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185 IF( J-START.GT.ENDD-J-1 ) THEN |
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186 STKPNT = STKPNT + 1 |
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187 STACK( 1, STKPNT ) = START |
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188 STACK( 2, STKPNT ) = J |
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189 STKPNT = STKPNT + 1 |
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190 STACK( 1, STKPNT ) = J + 1 |
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191 STACK( 2, STKPNT ) = ENDD |
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192 ELSE |
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193 STKPNT = STKPNT + 1 |
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194 STACK( 1, STKPNT ) = J + 1 |
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195 STACK( 2, STKPNT ) = ENDD |
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196 STKPNT = STKPNT + 1 |
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197 STACK( 1, STKPNT ) = START |
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198 STACK( 2, STKPNT ) = J |
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199 END IF |
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200 ELSE |
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201 * |
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202 * Sort into increasing order |
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203 * |
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204 I = START - 1 |
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205 J = ENDD + 1 |
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206 90 CONTINUE |
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207 100 CONTINUE |
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208 J = J - 1 |
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209 IF( D( J ).GT.DMNMX ) |
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210 $ GO TO 100 |
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211 110 CONTINUE |
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212 I = I + 1 |
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213 IF( D( I ).LT.DMNMX ) |
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214 $ GO TO 110 |
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215 IF( I.LT.J ) THEN |
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216 TMP = D( I ) |
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217 D( I ) = D( J ) |
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218 D( J ) = TMP |
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219 GO TO 90 |
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220 END IF |
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221 IF( J-START.GT.ENDD-J-1 ) THEN |
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222 STKPNT = STKPNT + 1 |
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223 STACK( 1, STKPNT ) = START |
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224 STACK( 2, STKPNT ) = J |
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225 STKPNT = STKPNT + 1 |
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226 STACK( 1, STKPNT ) = J + 1 |
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227 STACK( 2, STKPNT ) = ENDD |
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228 ELSE |
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229 STKPNT = STKPNT + 1 |
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230 STACK( 1, STKPNT ) = J + 1 |
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231 STACK( 2, STKPNT ) = ENDD |
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232 STKPNT = STKPNT + 1 |
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233 STACK( 1, STKPNT ) = START |
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234 STACK( 2, STKPNT ) = J |
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235 END IF |
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236 END IF |
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237 END IF |
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238 IF( STKPNT.GT.0 ) |
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239 $ GO TO 10 |
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240 RETURN |
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241 * |
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242 * End of DLASRT |
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243 * |
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244 END |
