base/random.cc

   1 /*
   2  * Copyright (c) 2003 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
  29 #include <cstdlib>
  30 #include <cmath>
  31
  32 #include "sim/param.hh"
  33 #include "base/random.hh"
  34
  35 using namespace std;
  36
  37 class RandomContext : public ParamContext
  38 {
  39   public:
  40     RandomContext(const string &_iniSection)
  41         : ::ParamContext(_iniSection) {}
  42     ~RandomContext();
  43
  44     void checkParams();
  45 };
  46
  47 RandomContext paramContext("random");
  48
  49 Param<unsigned>
  50 seed(&paramContext, "seed", "seed to random number generator", 1);
  51
  52 void
  53 RandomContext::checkParams()
  54 {
  55     ::srandom(seed);
  56 }
  57
  58 long
  59 getLong()
  60 {
  61     return random();
  62 }
  63
  64 // idea for generating a double from erand48
  65 double
  66 getDouble()
  67 {
  68     union {
  69         uint32_t _long[2];
  70         uint16_t _short[4];
  71     };
  72
  73     _long[0] = random();
  74     _long[1] = random();
  75
  76     return ldexp((double) _short[0], -48) +
  77         ldexp((double) _short[1], -32) +
  78         ldexp((double) _short[2], -16);
  79 }