Hi Franck,
thanks for your kind words.

Talking about the average +60 elo points per speed doubling, it is indeed known, but I think it is relevant for computer performance in the context of either doubling the hardware speed, or allowing twice the time to move (and symetrically -60 for reducing 2 times), and in a limited range of times you apply this forecast. By the way, it might be up to +80 for the first doubling, then ramping down to the average +60, and less, should you continue doubling speed or time.

I think it does not apply to severely throttling the program with a max number of nodes: The King moves instantly, or so. We are not in the area where The King would be on brakes by a few times less computing power, where the +/- 60 would apply.

And keep in mind we are trying to baseline an elo level at active chess - meaning opponents fully benefit from 30s thinking time per move (plus pondering on operator time to move, at least, for those able to). So we have no experience nor reference there.

Anyway, a linear interpolation (a line, to keep it simple) applied to a log function is exactly what I did to provide the first table I posted. And it shew +199 elo points per doubling. It was not so bad an approximation as far as the range was that of the easy levels, but would have provided definitely incorrect results at higher nodes/move (elo 3500@ 1million nodes, wtf )

Why do I write about 1M nodes/move? The unthrottled King computes in the area of 30.000 nodes/s, so needs 33seconds thinking time (as an order of magnitude) to reach this amount. We are in the area of active chess...

The latest formula I provided would forecast slightly more than 2400 elo, unthrottled at active chess. Not so bad a forecast, isn't it?

Kind regards,
Eric