random.cc revision 7575:0002812cefe5 
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
38using namespace std;
39
40Random::Random()
41{
42    // default random seed taken from original source
43    init(5489);
44}
45
46Random::Random(uint32_t s)
47{
48    init(s);
49}
50
51Random::Random(uint32_t init_key[], int key_length)
52{
53    init(init_key, key_length);
54}
55
56Random::~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.
65uint32_t
66Random::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
81uint64_t
82Random::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
98void
99Random::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
107void
108Random::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
120Random random_mt;
121