From 4c9004671af455a03acb4e2750b12d62b2b3c917 Mon Sep 17 00:00:00 2001 From: Ferenc Arn Date: Sat, 14 Jan 2017 23:34:51 -0600 Subject: Replace the existing PRNG (Xorshift31) with (minimal) PCG (XSH-RR variant with 32-bit output, 64-bit state). PCG is better than many alternatives by many metrics (see www.pcg-random.org) including statistical quality with good speed. --- core/math/pcg.cpp | 15 +++++++++++++++ 1 file changed, 15 insertions(+) create mode 100644 core/math/pcg.cpp (limited to 'core/math/pcg.cpp') diff --git a/core/math/pcg.cpp b/core/math/pcg.cpp new file mode 100644 index 0000000000..eac3b36d36 --- /dev/null +++ b/core/math/pcg.cpp @@ -0,0 +1,15 @@ +// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org +// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website) + +#include "pcg.h" + +uint32_t pcg32_random_r(pcg32_random_t* rng) +{ + uint64_t oldstate = rng->state; + // Advance internal state + rng->state = oldstate * 6364136223846793005ULL + (rng->inc|1); + // Calculate output function (XSH RR), uses old state for max ILP + uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u; + uint32_t rot = oldstate >> 59u; + return (xorshifted >> rot) | (xorshifted << ((-rot) & 31)); +} -- cgit v1.2.3