Tapered Eval in Fruit

[gflohr]

I am trying to understand the implementation of Tapered Eval in Fruit: https://www.chessprogramming.org/Tapere ... on_example

PawnPhase is 0 there, and therefore all multiplications with PawnPhase are useless, and actually TotalPhase is just 24 and not 256 like the code suggests, hence the phase is between 0 and 24.

I have also checked the sources of Fruit and it looks like the copy of it in the wiki is correct.

Did I miss something here?

[Desperado]

I am trying to understand the implementation of Tapered Eval in Fruit: https://www.chessprogramming.org/Tapere ... on_example

PawnPhase is 0 there, and therefore all multiplications with PawnPhase are useless, and actually TotalPhase is just 24 and not 256 like the code suggests, hence the phase is between 0 and 24.

I have also checked the sources of Fruit and it looks like the copy of it in the wiki is correct.

Did I miss something here?

I guess this will provide you the answer.
Especially this part

[op12no2]

The last line of the code you linked to scales phase to [0,256] assuming integer arithmetic. I would guess because phase changes slower than eval is called, so you can use shifts in eval not division for the tapering.

[gflohr]

I guess this will provide you the answer.
Especially this part

Thanks! That's what I missed to find.

[gflohr]

The last line of the code you linked to scales phase to [0,256] assuming integer arithmetic. I would guess because phase changes slower than eval is called, so you can use shifts in eval not division for the tapering.

But doesn't that essentially ignore the number of pawns on the board?

[op12no2]

But doesn't that essentially ignore the number of pawns on the board?

Yes, using that scheme they don't contribute to phase. But you can try other values and see what happens...

[gflohr]

But doesn't that essentially ignore the number of pawns on the board?

Yes, using that scheme they don't contribute to phase. But you can try other values and see what happens...

Okay, but why? Aren't 16 pawns on the board very middle-game and zero very end-game?

[op12no2]

Okay, but why? Aren't 16 pawns on the board very middle-game and zero very end-game?

I don't think there is a good answer other than it seems to work; amongst probably endless other schemes (some including pawns) that also work. The weights can also be tuned, so pick something that seems sensible to you and then tune later perhaps.

[gflohr]

Okay, but why? Aren't 16 pawns on the board very middle-game and zero very end-game?

I don't think there is a good answer other than it seems to work; amongst probably endless other schemes (some including pawns) that also work. The weights can also be tuned, so pick something that seems sensible to you and then tune later perhaps.

I will try to update the wiki. And kudos for Lozza, btw.

[op12no2]

I will try to update the wiki. And kudos for Lozza, btw.

Cheers Guido, Lozza is a fun background project...