chaos and the LGP-30

Bill Degnan billdegnan at
Mon Jul 27 06:44:15 CDT 2020

On Sun, Jul 26, 2020, 8:44 PM Jecel Assumpcao Jr via cctalk <
cctalk at> wrote:

> Jay Jaeger wrote on Sun, 26 Jul 2020 19:24:24 -0500
> > So, either he mis-entered something, or possibly the result of a
> > different state of a random number generator somewhere?
> He dumped the full state of the simulation to paper with six digits
> after the decimal point even though the internal calculations used eight
> digits (I don't remember the actual precisions involved). So when he
> restarted the simulation from the middle he introduced errors of less
> than 1 per million and fully expected the results to be the same for the
> days he had already simulated so he could continue a little further. But
> he was shocked that the simulation went in a different direction and the
> results were totally different after only a few days.
> This is an absurd sensitivity to initial conditions that had never been
> noticed in any system before. He compared it to whether a butterfly
> flapped its wings or not in the middle of the Amazon making a difference
> on there being a nice day or a huge storm on the other side of the world
> a week later. This is the infamous "butterfly effect".
> All this came after eliminating all kinds of possible errors, of course.
> The first thing we thought back then when something like this happened
> was not "I found a new theory" but "the hardware is probably flaky or
> there is a compiler bug".
> - Jecel

Does the code listing exist on the web?


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