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flok

see

Post by flok » Tue Nov 28, 2017 1:11 pm

Hi,

Given:
[D]K7/8/k2n1n2/8/2q1P3/8/3N1N2/8 b - -[/D]

and:
pawn = 100
queen = 975
knight = 325

The left black queen is attacking the white pawn. What should be the SEE value?
First it is -975 for the attacking queen, then +100 for the pawn, -325 for the black knight, +325 for the white knight, -325 again and +325 again so I think it is -875. Am I right?

AlvaroBegue
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Re: see

Post by AlvaroBegue » Tue Nov 28, 2017 1:30 pm

No, that's not it at all. It's -550. I can break it down if you can't figure it out. But don't start with the material value of the queen, because the pawn is the first thing to go.

tomitank
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Re: see

Post by tomitank » Tue Nov 28, 2017 1:32 pm

flok wrote:Hi,

and:
pawn = 100
queen = 975
knight = 325

The left black queen is attacking the white pawn. What should be the SEE value?
First it is -975 for the attacking queen, then +100 for the pawn, -325 for the black knight, +325 for the white knight, -325 again and +325 again so I think it is -875. Am I right?
Hi!
pawn - queen + WKnight - BKnight + WKnight

100 - 975 + 325 - 325 + 325 = 550

flok

Re: see

Post by flok » Tue Nov 28, 2017 1:38 pm

tomitank wrote:100 - 975 + 325 - 325 + 325 = 550
AlvaroBegue wrote:No, that's not it at all. It's -550. I can break it down if you can't figure it out. But don't start with the material value of the queen, because the pawn is the first thing to go.
Please do because I can't figure it out.
First of all: why an odd number of additions? there are 6 pieces?

tomitank
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Re: see

Post by tomitank » Tue Nov 28, 2017 1:43 pm

flok wrote:
tomitank wrote:100 - 975 + 325 - 325 + 325 = 550
AlvaroBegue wrote:No, that's not it at all. It's -550. I can break it down if you can't figure it out. But don't start with the material value of the queen, because the pawn is the first thing to go.
Please do because I can't figure it out.
First of all: why an odd number of additions? there are 6 pieces?
The last attacker piece is a Black Knight.

AlvaroBegue
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Location: New York

Re: see

Post by AlvaroBegue » Tue Nov 28, 2017 1:49 pm

flok wrote:
tomitank wrote:100 - 975 + 325 - 325 + 325 = 550
AlvaroBegue wrote:No, that's not it at all. It's -550. I can break it down if you can't figure it out. But don't start with the material value of the queen, because the pawn is the first thing to go.
Please do because I can't figure it out.
First of all: why an odd number of additions? there are 6 pieces?
But there are only 5 captures.

Let's imagine the sequence of moves if everyone captures everything till the end (although they don't have to: Either player could stop and take the "stand pat" score, like in quiescence search).

qxP, Nxq, nxN, Nxn, nxN

Let's write down the sequence of captured piece values, with sign:
+100, -975, +325, -325, +325

Now compute the partial sums (material balance at each step):
+100, -875, -550, -875, -550

Now start at the penultimate place in the list (the second -875) and think of whether the player to move would prefer the material balance at that time (the number we are looking at) or the result of the recapture (the next element in the list).

+100, -875, -550, >>-875<<, -550

In this case it was black's turn, and black would rather see -550 than -875, because in the convention of signs we are using in this post, higher means better for black. So we replace the -875 with -550 and we move back.

+100, -875, >>-550<<, -550, -550

White is indifferent as to whether to pick the -550 from not standing pat or the -550 from recapturing.

+100, >>-875<<, -550, -550, -550

It's black's turn, so black would rather take the -550 from recapturing.

>>+100<<, -550, -550, -550, -550

It's white's turn, so -550 is better than +100.

-550, -550, -550, -550, -550

The result of SEE is the first number, so -550.

elcabesa
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Re: see

Post by elcabesa » Tue Nov 28, 2017 3:26 pm

I haven't understood if you correctly understood the see.
The see is relative to a move.
In this position queen capturing the pawn has a see of -550.
Left Knight capturing pawn has a see of 100
Right knight capturing pawn had a see of 100.

I have calculated the see by mind.. and they can be wrong. But the important thing is that a move has a see.
A see without the first move doesn't exist

AlvaroBegue
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Re: see

Post by AlvaroBegue » Tue Nov 28, 2017 3:58 pm

elcabesa wrote:I haven't understood if you correctly understood the see.
The see is relative to a move.
In this position queen capturing the pawn has a see of -550.
Left Knight capturing pawn has a see of 100
Right knight capturing pawn had a see of 100.

I have calculated the see by mind.. and they can be wrong. But the important thing is that a move has a see.
A see without the first move doesn't exist
Well, he said this: "The left black queen is attacking the white pawn. What should be the SEE value?"

I assume in this whole thread we have been talking about the SEE value of the black queen capturing the white pawn.

elcabesa
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Re: see

Post by elcabesa » Tue Nov 28, 2017 4:35 pm

Me too.
But since I don't know what are the knowledge of folkert and the post doesn't specify it very well, I have specified it.

flok

Re: see

Post by flok » Tue Nov 28, 2017 7:34 pm

I think I understand it :-)
It's just that I find it difficult to get it right.
But the current version does all 3 cases right! (queen/knight/knight as attacker giving -550, 100 and 100)

Thank you all.


(more testcases welcome but don't feel obliged :-)

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