1 | /* glprng02.c */ |
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2 | |
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3 | /*********************************************************************** |
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4 | * This code is part of GLPK (GNU Linear Programming Kit). |
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5 | * |
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6 | * Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, |
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7 | * 2009, 2010 Andrew Makhorin, Department for Applied Informatics, |
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8 | * Moscow Aviation Institute, Moscow, Russia. All rights reserved. |
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9 | * E-mail: <mao@gnu.org>. |
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10 | * |
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11 | * GLPK is free software: you can redistribute it and/or modify it |
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12 | * under the terms of the GNU General Public License as published by |
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13 | * the Free Software Foundation, either version 3 of the License, or |
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14 | * (at your option) any later version. |
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15 | * |
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16 | * GLPK is distributed in the hope that it will be useful, but WITHOUT |
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17 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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18 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public |
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19 | * License for more details. |
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20 | * |
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21 | * You should have received a copy of the GNU General Public License |
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22 | * along with GLPK. If not, see <http://www.gnu.org/licenses/>. |
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23 | ***********************************************************************/ |
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24 | |
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25 | #include "glpenv.h" |
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26 | #include "glprng.h" |
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27 | #define xfault xerror |
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28 | |
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29 | /*********************************************************************** |
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30 | * NAME |
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31 | * |
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32 | * rng_unif_01 - obtain pseudo-random number in the range [0, 1] |
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33 | * |
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34 | * SYNOPSIS |
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35 | * |
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36 | * #include "glprng.h" |
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37 | * double rng_unif_01(RNG *rand); |
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38 | * |
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39 | * RETURNS |
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40 | * |
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41 | * The routine rng_unif_01 returns a next pseudo-random number which is |
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42 | * uniformly distributed in the range [0, 1]. */ |
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43 | |
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44 | double rng_unif_01(RNG *rand) |
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45 | { double x; |
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46 | x = (double)rng_next_rand(rand) / 2147483647.0; |
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47 | xassert(0.0 <= x && x <= 1.0); |
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48 | return x; |
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49 | } |
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50 | |
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51 | /*********************************************************************** |
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52 | * NAME |
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53 | * |
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54 | * rng_uniform - obtain pseudo-random number in the range [a, b] |
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55 | * |
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56 | * SYNOPSIS |
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57 | * |
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58 | * #include "glprng.h" |
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59 | * double rng_uniform(RNG *rand, double a, double b); |
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60 | * |
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61 | * RETURNS |
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62 | * |
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63 | * The routine rng_uniform returns a next pseudo-random number which is |
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64 | * uniformly distributed in the range [a, b]. */ |
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65 | |
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66 | double rng_uniform(RNG *rand, double a, double b) |
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67 | { double x; |
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68 | if (a >= b) |
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69 | xfault("rng_uniform: a = %g, b = %g; invalid range\n", a, b); |
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70 | x = rng_unif_01(rand); |
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71 | x = a * (1.0 - x) + b * x; |
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72 | xassert(a <= x && x <= b); |
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73 | return x; |
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74 | } |
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75 | |
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76 | /* eof */ |
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