On Sun, Jul 26, 2020, 8:44 PM Jecel Assumpcao Jr via cctalk < cctalk@classiccmp.org> 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? Bill >
