Errata

  • the word ‘humanity’ can mean 1) the entirety of mankind or 2) empathy.
    A good  disambiguation would have been to consistently use a capital ‘H’ for 1)
  • inline book titles are named inconsistently (bold, italic, single quotes)
  • p.3 “‘The Mule’ revives and appropriates the old empire”
    More accurately, he exploits the power vacuum created by the Empire’s disintegration
  • p.5 The physics explanation for decreased size = increased speed is wrong (and is still a widespread misconception long after classical electromagnetism was worked out). Electrical energy is propagated not simply through wires, but through fields in the space around the wires, at or near c, the speed of light in a vacuum. Inductance, capacitance, and electromagnetic radiation are all at play. Decreased transistor size results in less heat and resistance, leading to improved efficiency – thus faster gate switching. The quantitative comparison remains largely correct however, which was the main point.
  • p.6 “Each core in a GPU is a central processing unit (CPU) in its own right”
    That’s overstating it, at least for 2011. GPUs are optimized for Single Instruction, Multiple Data (SIMD) processing which is highly ‘synchronous’. More general programming requires Multiple Instruction, Multiple Data (MIMD) processing which is more ‘asynchronous’. There is work under way on how to run more general programs on GPU hardware, called MIMD on GPU or ‘MOG’. In any case, in this article, GPU is really just used as a euphemism for ‘dirt cheap mountain of transistors’
  • p.7 “to infer a revised probability”
    Correction: “to produce a revised probablility”
  • p.11 The formula given is the Julia set. The Mandelbrot set is drawn by iterating   zn+1 = zn2 + c      where z0 = 0,  |zn| < some ‘bailout’ factor
  • p.11 “Fractals offer a glimpse into the construction mechanisms of nature”
    Here I have made one of the mistakes that I am usually on the look-out for, namely the anthropomorphization of nature. Nature is a realm of computation and evolution. Math is one of the tools that allows a vastly simplified model of that realm to be stored in a 3-pound hominid brain. Daisies and snails know nothing of math. At least I was wise enough to add the “offer a glimpse” qualifier instead of implying that nature intentionally uses fractals.
  • p.17 “may be possible to accurately model a form of psychohistory”
    Correction: “may be possible to computationally model a form of psychohistory”
  • p.18 “Asimov, I. (1952). Foundation and Empire. New York: Gome Press”
    Correction: Gnome Press

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