## modules/up/src/Core/gnu/MLCG.cc

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## FUNCTIONS

This source file includes following functions.

1. MLCG
2. reset
3. asLong

       1 // This may look like C code, but it is really -*- C++ -*-
       2 /*
       3 Copyright (C) 1989 Free Software Foundation
       4
       5 This file is part of the GNU C++ Library.  This library is free
       6 software; you can redistribute it and/or modify it under the terms of
       7 the GNU Library General Public License as published by the Free
       8 Software Foundation; either version 2 of the License, or (at your
       9 option) any later version.  This library is distributed in the hope
      10 that it will be useful, but WITHOUT ANY WARRANTY; without even the
      11 implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
      12 PURPOSE.  See the GNU Library General Public License for more details.
      13 You should have received a copy of the GNU Library General Public
      14 License along with this library; if not, write to the Free Software
      15 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
      16 */
      17 #ifdef __GNUG__
      18 #pragma implementation
      19 #endif
      20 #include "gnu/MLCG.h"
      21 //
      22 //      SEED_TABLE_SIZE must be a power of 2
      23 //
      24
      25
      26 #define SEED_TABLE_SIZE 32
      27
      28 static _G_int32_t seedTable[SEED_TABLE_SIZE] = {
      29 0xbdcc47e5, 0x54aea45d, 0xec0df859, 0xda84637b,
      30 0xc8c6cb4f, 0x35574b01, 0x28260b7d, 0x0d07fdbf,
      31 0x9faaeeb0, 0x613dd169, 0x5ce2d818, 0x85b9e706,
      32 0xab2469db, 0xda02b0dc, 0x45c60d6e, 0xffe49d10,
      33 0x7224fea3, 0xf9684fc9, 0xfc7ee074, 0x326ce92a,
      34 0x366d13b5, 0x17aaa731, 0xeb83a675, 0x7781cb32,
      35 0x4ec7c92d, 0x7f187521, 0x2cf346b4, 0xad13310f,
      36 0xb89cff2b, 0x12164de1, 0xa865168d, 0x32b56cdf
      37 };
      38
      39 MLCG::MLCG(_G_int32_t seed1, _G_int32_t seed2)
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      40 {
      41     initialSeedOne = seed1;
      42     initialSeedTwo = seed2;
      43     reset();
      44 }
      45
      46 void
      47 MLCG::reset()
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      48 {
      49     _G_int32_t seed1 = initialSeedOne;
      50     _G_int32_t seed2 = initialSeedTwo;
      51
      52     //
      53     //  Most people pick stupid seed numbers that do not have enough
      54     //  bits. In this case, if they pick a small seed number, we
      55     //  map that to a specific seed.
      56     //
      57     if (seed1 < 0) {
      58         seed1 = (seed1 + 2147483561);
      59         seed1 = (seed1 < 0) ? -seed1 : seed1;
      60     }
      61
      62     if (seed2 < 0) {
      63         seed2 = (seed2 + 2147483561);
      64         seed2 = (seed2 < 0) ? -seed2 : seed2;
      65     }
      66
      67     if (seed1 > -1 && seed1 < SEED_TABLE_SIZE) {
      68         seedOne = seedTable[seed1];
      69     } else {
      70         seedOne = seed1 ^ seedTable[seed1 & (SEED_TABLE_SIZE-1)];
      71     }
      72
      73     if (seed2 > -1 && seed2 < SEED_TABLE_SIZE) {
      74         seedTwo = seedTable[seed2];
      75     } else {
      76         seedTwo = seed2 ^ seedTable[ seed2 & (SEED_TABLE_SIZE-1) ];
      77     }
      78     seedOne = (seedOne % 2147483561) + 1;
      79     seedTwo = (seedTwo % 2147483397) + 1;
      80 }
      81
      82 _G_uint32_t MLCG::asLong()
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      83 {
      84     _G_int32_t k = seedOne % 53668;
      85
      86     seedOne = 40014 * (seedOne-k * 53668) - k * 12211;
      87     if (seedOne < 0) {
      88         seedOne += 2147483563;
      89     }
      90
      91     k = seedTwo % 52774;
      92     seedTwo = 40692 * (seedTwo - k * 52774) - k * 3791;
      93     if (seedTwo < 0) {
      94         seedTwo += 2147483399;
      95     }
      96
      97     _G_int32_t z = seedOne - seedTwo;
      98     if (z < 1) {
      99         z += 2147483562;
     100     }
     101     return( (unsigned long) z);
     102 }
     103

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