How much elo is pondering worth?

[bob]

Quad core. Two of the cores were not being used during the ponder on test.

The ponder off test was conducted using cutechess with concurrency = 3. So three matches were running at a time.

That's a big gain, unless we are talking very fast time controls. I typically see 50-70 for doubling the speed or time per move. Pondering can't consistently give even a 50% speedup, because of the way the two programs get into a ponder-hit-ponder-hit cycle, and SOMEBODY has to think for 3 minutes or whatever.

Realistically, the last time I measured this, the time savings averaged about 30% over a 30K match on my cluster. That's probably close to 20 Elo or a bit more, at least for my code.

The ponder off games were played for the CCRL 40/4 (40 moves in 4 minutes on the CCRL reference computer) database. For my computer, the roughly equivalent time control is 40 moves in 155 seconds.

A few weeks later, there was some discussion at TCEC about whether using all cores with ponder off produced higher quality games than using half the cores with ponder on. I decided to see how much better Gaviota performed on one core while pondering as compared to one core and ponder off. I compared the ponder on games against the ponder off games, using the same opponents and the same positions.

On my computer (based on several experiments), the strength increase when doubling the speed at 40/155 seconds is somewhere around 70 to 90 Elo. This roughly agrees with what other people have found.

66 Elo does seem a bit high. However, only 750 games were played, so the true gain for Gaviota on my computer at that time control could be more like 45 Elo.

There is another piece of data that supports my result. Frank Quisinsky (google SWCR chess) created a ponder on rating list a couple of years ago, using a time control and processor that was roughly equivalent to 40/15 CEGT (so longer than my games). He did an experiment with Crafty 23.3 64bit, playing games with ponder off in addition to the ponder on games. I am not sure if he used exactly the same conditions (same opponents and same openings), but he measured a gain of 46 Elo.

That's not far from what I would guess. But it is also sensitive to the opponents. Weak opponents will produce lower prediction rates and make the gain smaller. Strong opponents will increase the prediction rate.