random.cc revision 8658:f1a69b7246f7 
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 <limits>
33#include "base/fenv.hh"
34#include "base/intmath.hh"
35#include "base/misc.hh"
36#include "base/random.hh"
37#include "sim/serialize.hh"
38
39using namespace std;
40
41Random::Random()
42{
43    // default random seed taken from original source
44    init(5489);
45}
46
47Random::Random(uint32_t s)
48{
49    init(s);
50}
51
52Random::Random(uint32_t init_key[], int key_length)
53{
54    init(init_key, key_length);
55}
56
57Random::~Random()
58{
59}
60
61// To preserve the uniform random distribution between min and max,
62// and allow all numbers to be represented, we generate a uniform
63// random number to the nearest power of two greater than max.  If
64// this number doesn't fall between 0 and max, we try again.  Anything
65// else would skew the distribution.
66uint32_t
67Random::genrand(uint32_t max)
68{
69    if (max == 0)
70        return 0;
71    if (max == std::numeric_limits<uint32_t>::max())
72        return genrand();
73
74    int log = ceilLog2(max + 1);
75    int shift = (sizeof(uint32_t) * 8 - log);
76    uint32_t random;
77
78    do {
79        random = genrand() >> shift;
80    } while (random > max);
81
82    return random;
83}
84
85uint64_t
86Random::genrand(uint64_t max)
87{
88    if (max == 0)
89        return 0;
90    if (max == std::numeric_limits<uint64_t>::max())
91        return genrand();
92
93    int log = ceilLog2(max + 1);
94    int shift = (sizeof(uint64_t) * 8 - log);
95    uint64_t random;
96
97    do {
98        random = (uint64_t)genrand() << 32 | (uint64_t)genrand();
99        random = random >> shift;
100    } while (random > max);
101
102    return random;
103}
104
105void
106Random::serialize(const string &base, ostream &os)
107{
108    int length = N;
109    paramOut(os, base + ".mti", mti);
110    paramOut(os, base + ".length", length);
111    arrayParamOut(os, base + ".data", mt, length);
112}
113
114void
115Random::unserialize(const string &base, Checkpoint *cp, const string &section)
116{
117    int length;
118
119    paramIn(cp, section, base + ".mti", mti);
120    paramIn(cp, section, base + ".length", length);
121    if (length != N)
122        panic("cant unserialize random number data. length != %d\n", length);
123
124    arrayParamIn(cp, section, base + ".data", mt, length);
125}
126
127Random random_mt;
128