On Fri, Mar 11, 2016 at 3:10 AM, Reimar Döffinger <reimar.doeffin...@gmx.de> wrote: > On 11.03.2016, at 05:16, Ganesh Ajjanagadde <gajja...@gmail.com> wrote: >> Code taken from the Julia project, licensed under MIT: >> https://github.com/JuliaLang/julia/blob/master/base/random.jl, in turn >> derived from: "The Ziggurat Method for generating random variables" - >> Marsaglia and Tsang. >> >> Paper and reference code: http://www.jstatsoft.org/v05/i08/. This is >> well known to be the fastest method empirically for generating normal random >> variables. Note that there are a large number of implementations with >> various tunings, this was one of the simpler ones and also has a friendly >> license. > > I absolutely can't see how this could be the fastest considering it uses the > rather slow av_lfg_get twice, unless you only mean the part of getting floats > in a certain distribution and not the actual randomness.
That is what I meant, all random generators use a uniform bitstream at their core regardless and then transform it somehow. For example, the linked arxiv paper (fastest I could fine) uses a SIMD optimized Mersenne twister variant. > I asked a long time ago for the decoder, but never got an answer why we use > lfg and not a much faster lcg. I guess there is no inherent reason. I recall Michael's general analysis: http://guru.multimedia.cx/category/pseudo-random-number-generators/. > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
