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
40 * Return non-zero with probability D.
45 return d > (random() % 32768) / 32768.0;
49 * Return non-zero with probability PCT%.
54 return roll(100) <= pct;
58 round_up_to_pow2(unsigned val)
71 * Return a random number in [0..N-1].
72 * N must be in [1..2^31-1].
77 unsigned pow2 = round_up_to_pow2(n);
81 r = random() & (pow2 - 1);
87 * Return a random number in [1..N].
88 * N must be in [0..2^31-1].
97 * Round VAL to nearest integer (on the average).
98 * VAL's fractional part is chance to round up.
103 double flr = floor(val);
104 return (int)(flr + chance(val - flr));
108 * Seed the pseudo-random number generator with SEED.
109 * The sequence of pseudo-random numbers is repeatable by seeding it
110 * with the same value.
113 seed_prng(unsigned seed)