From 31faa1f22626b8745ed4a1541497832b6f595df2 Mon Sep 17 00:00:00 2001 From: Yuri Roubinsky Date: Thu, 29 Oct 2020 15:40:53 +0300 Subject: Fix biased output of randi_range --- core/math/random_number_generator.h | 16 +++++++++++----- core/math/random_pcg.h | 4 ++++ 2 files changed, 15 insertions(+), 5 deletions(-) (limited to 'core/math') diff --git a/core/math/random_number_generator.h b/core/math/random_number_generator.h index 416e52ea87..2e7941b345 100644 --- a/core/math/random_number_generator.h +++ b/core/math/random_number_generator.h @@ -58,12 +58,18 @@ public: _FORCE_INLINE_ real_t randfn(real_t mean = 0.0, real_t deviation = 1.0) { return randbase.randfn(mean, deviation); } _FORCE_INLINE_ int randi_range(int from, int to) { - unsigned int ret = randbase.rand(); - if (to < from) { - return ret % (from - to + 1) + to; - } else { - return ret % (to - from + 1) + from; + int range; + int min; + if (to > from) { + range = to - from + 1; + min = from; + } else if (to < from) { + range = from - to + 1; + min = to; + } else { // from == to + return from; } + return randbase.rand(range) + min; } RandomNumberGenerator() {} diff --git a/core/math/random_pcg.h b/core/math/random_pcg.h index 09b13ab74d..dfdae53eed 100644 --- a/core/math/random_pcg.h +++ b/core/math/random_pcg.h @@ -81,6 +81,10 @@ public: current_seed = pcg.state; return pcg32_random_r(&pcg); } + _FORCE_INLINE_ uint32_t rand(uint32_t bounds) { + current_seed = pcg.state; + return pcg32_boundedrand_r(&pcg, bounds); + } // Obtaining floating point numbers in [0, 1] range with "good enough" uniformity. // These functions sample the output of rand() as the fraction part of an infinite binary number, -- cgit v1.2.3