Page 2 of 2

Re: Alternating Scores

Posted: Wed Feb 09, 2011 6:08 pm
by Evert
evandam wrote:Ok I looked at the eval a little closer. To simplify, I took out everything except the material evaluation. Turns out I have the piece values set at 1 3 3.1 7 10 (for P N B R Q). I also simplified this to 1 3 3 7 10. So again from.
Shouldn't matter.
5rk1/pp4p1/2n1p2p/2Npq3/2p5/6P1/P3P1BP/R4Q1K w - - 0 1

1 +7.00 Qxf8+
2 -3.00 Qxf8+ Kxf8
3 +1.00 Bf3 a5 Nxe6
4 -3.00 Nxb7 Rxf1+ Rxf1 Qxe2
5 +7.00 Qxf8+ Kxf8 Nd7+ Ke7 Nxe5

Initially both sides have 27. Qxf8+ and it is 27-20 (+7.00). Qxf8+ Kxf8 and it is 17-20 (-3.00) and so on.
What do you mean by "Qxf8+ is 27-20 (+7.00)"? Without quiescence, Qxf8 should just put you a rook ahead (+5.00). Where are those numbers coming from?
Related question: after 1... Kxf8 it's clear that 1. Qxf8 is a bad move, so why is that still selected as the best move after a two ply search?

Re: Alternating Scores

Posted: Wed Feb 09, 2011 7:42 pm
by evandam
Ok I looked at the eval a little closer. To simplify, I took out everything except the material evaluation. Turns out I have the piece values set at 1 3 3.1 7 10 (for P N B R Q). I also simplified this to 1 3 3 7 10. So again from.

Shouldn't matter.
No it shouldn't I was just simplifying the problem for the time being.
5rk1/pp4p1/2n1p2p/2Npq3/2p5/6P1/P3P1BP/R4Q1K w - - 0 1

1 +7.00 Qxf8+
2 -3.00 Qxf8+ Kxf8
3 +1.00 Bf3 a5 Nxe6
4 -3.00 Nxb7 Rxf1+ Rxf1 Qxe2
5 +7.00 Qxf8+ Kxf8 Nd7+ Ke7 Nxe5

Initially both sides have 27. Qxf8+ and it is 27-20 (+7.00). Qxf8+ Kxf8 and it is 17-20 (-3.00) and so on.

What do you mean by "Qxf8+ is 27-20 (+7.00)"? Without quiescence, Qxf8 should just put you a rook ahead (+5.00). Where are those numbers coming from?
Yes without quiescence. The +7.00 is a product of my piece values which in my case are 1 3 3 7 10 for P K B R Q. So that is where those numbers are coming from.

Related question: after 1... Kxf8 it's clear that 1. Qxf8 is a bad move, so why is that still selected as the best move after a two ply search?
Wrong. Look a bit closer. Both the wQ and wR are threatened. So that is the best move after a two ply search.

Re: Alternating Scores

Posted: Wed Feb 09, 2011 7:47 pm
by Evert
evandam wrote: Yes without quiescence. The +7.00 is a product of my piece values which in my case are 1 3 3 7 10 for P K B R Q. So that is where those numbers are coming from.
Right, I completely glossed over the fact that you're using a value of 7 rather than 5 for the rook.
Any particular reason for that?
Related question: after 1... Kxf8 it's clear that 1. Qxf8 is a bad move, so why is that still selected as the best move after a two ply search?
Wrong. Look a bit closer. Both the wQ and wR are threatened. So that is the best move after a two ply search.[/quote]
Right, ok. So yes, you do need a quiescence search. ;)

Re: Alternating Scores

Posted: Wed Feb 09, 2011 8:03 pm
by evandam
Evert wrote: Right, I completely glossed over the fact that you're using a value of 7 rather than 5 for the rook.
Any particular reason for that?
Not really. I have been sort of concentrating on the search algorithms for now, since the improvement there to me at least is more measurable than changes to the eval. I'll get around to it later.
Evert wrote: Right, ok. So yes, you do need a quiescence search. ;)
Don't feel bad. I had to run it though playing alternate moves against Crafty before I noticed it. Quiescence is next on my list.

Re: Alternating Scores

Posted: Wed Feb 09, 2011 10:51 pm
by bob
evandam wrote:Ok I looked at the eval a little closer. To simplify, I took out everything except the material evaluation. Turns out I have the piece values set at 1 3 3.1 7 10 (for P N B R Q). I also simplified this to 1 3 3 7 10. So again from.

5rk1/pp4p1/2n1p2p/2Npq3/2p5/6P1/P3P1BP/R4Q1K w - - 0 1

1 +7.00 Qxf8+
2 -3.00 Qxf8+ Kxf8
3 +1.00 Bf3 a5 Nxe6
4 -3.00 Nxb7 Rxf1+ Rxf1 Qxe2
5 +7.00 Qxf8+ Kxf8 Nd7+ Ke7 Nxe5

Initially both sides have 27. Qxf8+ and it is 27-20 (+7.00). Qxf8+ Kxf8 and it is 17-20 (-3.00) and so on.

If we can agree on that, and overlook the fact that maybe my piece values are bad etc. Quiescence sounds like the way to quite these swings.
You have to do something, or every time you move you will make a move that leaves a piece hanging at the last ply, which will greatly distort the search results...