WDL value head support

[Ttl]

WDL head support for all backends. Includes just the backend support and doesn't do anything yet with the draw information.

Needs updated protobuf: LeelaChessZero/lczero-common#6

Training code for replacing the old value head with WDL in existing old type network: https://github.com/Ttl/lczero-training/tree/wdl_surgery

11248 with WDL value head: http://hforsten.com/leelaz/11248-wdl.pb.gz (Obsolete due to protobuf changes)

Score of lc0_11248_wdl vs lc0_11248: 15 - 5 - 45 [0.577]
Elo difference: 53.88 +/- 46.33, LOS: 98.73 %, DrawRatio: 69.2 %

TC: 10+0.5s on GTX 1050 Ti

[Ttl]

Strength increase in testing is probably from the additional training on TB rescored test10 data instead of WDL head. I wouldn't expect it to be any stronger. All convolutional layers and policy head were set to non-trainable, so the only difference in this network is the fully connected layers of the value head.

Tests fail because protobuf needs to be updated.

[Ttl]

Added the tree search part. Previous commit also includes parameter for adjusting the score of the draw, but I removed since it didn't gain any Elo in testing. Verbose-move-stats was modified to report WDL scores for testing purposes.

Also I added WDL head to a test30 net that is much better at evaluating draws than test10 net. It can be downloaded at: http://hforsten.com/leelaz/256x20-32585-wdl-4000.pb.gz (Obsolete due to protobuf changes)

[Tilps]

Verbose stats still needs to print U. (And Q+U is convenient.)

[TFiFiE]

This implements #79, right? Like I said there, it would then also be possible to shorten the average training game length by allowing draws by agreement.

[Tilps]

Yes, but we can do that as a follow up PR.

[TFiFiE]

Previous commit also includes parameter for adjusting the score of the draw, but I removed since it didn't gain any Elo in testing.

But wouldn't the usefulness of that come from the ability to do stuff like force the engine to play for a draw or for a win or with some other contempt-like factor?

[Tilps]

Previous commit also includes parameter for adjusting the score of the draw, but I removed since it didn't gain any Elo in testing.

But wouldn't the usefulness of that come from the ability to do stuff like force the engine to play for a draw or for a win or with some other contempt-like factor?

More work can be done on this aspect after the PR is submitted.

[Ttl]

Needs modifications for protobuf changes in: LeelaChessZero/lczero-common#8

[TFiFiE]

Maybe change https://github.com/orgs/LeelaChessZero/projects/1#card-10518034 to point to this instead?

[Ttl]

Merged with master and implemented the protobuf changes.

Test network with WDL value head and convolutional policy head: http://hforsten.com/leelaz/128x10-az-pol-map-wdl-200000.pb.gz

[borg323]

Just tested that 32 bit builds work.

[lp200]

iirc, currently move_count is disabled
when it enable, will not it help to judge the draw more accurately?