src/base/random.cc

   1 /*
   2  * Copyright (c) 2003-2005 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Nathan Binkert
  29  *          Ali Saidi
  30  */
  31
  32 #include "base/fenv.hh"
  33 #include "base/intmath.hh"
  34 #include "base/misc.hh"
  35 #include "base/random.hh"
  36 #include "sim/serialize.hh"
  37
  38 using namespace std;
  39
  40 Random::Random()
  41 {
  42     // default random seed taken from original source
  43     init(5489);
  44 }
  45
  46 Random::Random(uint32_t s)
  47 {
  48     init(s);
  49 }
  50
  51 Random::Random(uint32_t init_key[], int key_length)
  52 {
  53     init(init_key, key_length);
  54 }
  55
  56 Random::~Random()
  57 {
  58 }
  59
  60 // To preserve the uniform random distribution between min and max,
  61 // and allow all numbers to be represented, we generate a uniform
  62 // random number to the nearest power of two greater than max.  If
  63 // this number doesn't fall between 0 and max, we try again.  Anything
  64 // else would skew the distribution.
  65 uint32_t
  66 Random::genrand(uint32_t max)
  67 {
  68     if (max == 0)
  69         return 0;
  70     int log = ceilLog2(max) + 1;
  71     int shift = (sizeof(uint32_t) * 8 - log);
  72     uint32_t random;
  73
  74     do {
  75         random = genrand() >> shift;
  76     } while (random > max);
  77
  78     return random;
  79 }
  80
  81 uint64_t
  82 Random::genrand(uint64_t max)
  83 {
  84     if (max == 0)
  85         return 0;
  86     int log = ceilLog2(max) + 1;
  87     int shift = (sizeof(uint64_t) * 8 - log);
  88     uint64_t random;
  89
  90     do {
  91         random = (uint64_t)genrand() << 32 | (uint64_t)genrand();
  92         random = random >> shift;
  93     } while (random > max);
  94
  95     return random;
  96 }
  97
  98 void
  99 Random::serialize(const string &base, ostream &os)
 100 {
 101     int length = N;
 102     paramOut(os, base + ".mti", mti);
 103     paramOut(os, base + ".length", length);
 104     arrayParamOut(os, base + ".data", mt, length);
 105 }
 106
 107 void
 108 Random::unserialize(const string &base, Checkpoint *cp, const string &section)
 109 {
 110     int length;
 111
 112     paramIn(cp, section, base + ".mti", mti);
 113     paramIn(cp, section, base + ".length", length);
 114     if (length != N)
 115         panic("cant unserialize random number data. length != %d\n", length);
 116
 117     arrayParamIn(cp, section, base + ".data", mt, length);
 118 }
 119
 120 Random random_mt;