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* math-util.c - Small math utilities shared by other modules
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* Fyre - rendering and interactive exploration of chaotic functions
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* Copyright (C) 2004-2005 David Trowbridge and Micah Dowty
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* Copyright (C) 2004-2006 David Trowbridge and Micah Dowty
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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float uniform_variate() {
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/* It's much faster to use our own global g_rand, rather than
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* relying on the g_random_* family of functions. Those functions
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* are thread-safe, and the locking around that shared g_rand can
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* take a very significant amount of CPU. We don't need thread-safe
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* random variates yet.
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static GRand* global_random = NULL;
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global_random = g_rand_new_with_seed(time(NULL));
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double uniform_variate() {
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/* A uniform random variate between 0 and 1 */
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return g_random_double();
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float normal_variate() {
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/* A unit-normal random variate, implemented with the Box-Muller method */
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return sqrt(-2*log(g_random_double())) * cos(g_random_double() * (2*M_PI));
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return g_rand_double(global_random);
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void normal_variate_pair(double *a, double *b) {
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/* Produce a pair of values with a standard normal distribution,
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* using the Polar Box-Mueller method.
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x = uniform_variate();
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y = uniform_variate();
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/* Squared radius. The vector must be nonzero,
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* and it must lie within the unit circle.
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} while (r2 > 1 || r2 == 0);
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/* Perform the Box-Mueller transform on each component */
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m = sqrt(-2.0 * log(r2) / r2);
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int int_variate(int minimum, int maximum) {
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return g_rand_int_range(global_random, minimum, maximum);
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int find_upper_pow2(int x) {
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src/math-util.c
