2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2013, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure, Markus Armbruster
6 * Empire is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 * See files README, COPYING and CREDITS in the root of the source
22 * tree for related information and legal notices. It is expected
23 * that future projects/authors will amend these files as needed.
29 * Known contributors to this file:
30 * Markus Armbruster, 2006-2012
38 #include "mt19937ar.h"
41 * Return non-zero with probability D.
46 return d > genrand_real2();
50 * Return non-zero with probability PCT%.
55 return roll(100) <= pct;
59 round_up_to_pow2(unsigned val)
72 * Return a random number in [0..N-1].
73 * N must be in [1..2^31-1].
78 unsigned pow2 = round_up_to_pow2(n);
82 r = genrand_int32() & (pow2 - 1);
88 * Return a random number in [1..N].
89 * N must be in [0..2^31-1].
98 * Round VAL to nearest integer (on the average).
99 * VAL's fractional part is chance to round up.
104 double flr = floor(val);
105 return (int)(flr + chance(val - flr));
109 * Seed the pseudo-random number generator with SEED.
110 * The sequence of pseudo-random numbers is repeatable by seeding it
111 * with the same value.
114 seed_prng(unsigned seed)