easy-hard moves (again)

[bob]

Apparently the position diagram was broken. The white queen is missing. Here is another try:

[d] 5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w - - 0 1

[Uri Blass]

Apparently the position diagram was broken. The white queen is missing. Here is another try:

[d] 5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w - - 0 1

I saw no missing queen.

It is the same position and it seems that both Bxh6 and Bf4 draw so Bxh6 is not the only non losing move.

[bob]

Apparently the position diagram was broken. The white queen is missing. Here is another try:

[d] 5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w - - 0 1

I saw no missing queen.

It is the same position and it seems that both Bxh6 and Bf4 draw so Bxh6 is not the only non losing move.

The diagram in YOUR post had no queen, I assumed it was the same as mine.

In any case, my original point still stands. Qxb6 looks easy at first. One does NOT want to play that move however. And later, there is another move that becomes "easy" but my current (and the suggested window approach) would not recognize a move that only looks easy as the search gets deeper..

[Evert]

Does it help to consider why the PV changed? I could imagine that it makes a difference whether the first move fails low (the former PV turns out to be bad/a trap, the position in the diagram) or whether another move becomes better than the PV move by itself. In the first case the move that looked good was a trap, but whatever move replaced it might still be a candidate for an "easy" move. In the second case there may be no obvious "easy" move.

Of course it may take some extra book keeping to make this distinction but it might be interesting to know the statistics at least.

[Evert]

Bxh6 is not the only move that saves the position for white.
It seems that Bf4 also saves the position for white

How?

[ernest]

Bxh6 is not the only move that saves the position for white.
It seems that Bf4 also saves the position for white

How?

After 1.Bf4

5r1k/6p1/1n2Q2p/4p3/5B2/7P/PP4PK/R3q3 b - - 0 1
Analysis by Houdini 3 w32 Nlm:
...............
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 Kf7 10.Kg3 f5 11.a5 Nb4 12.Kf4 Kg6 13.g3 h5 14.Ke3 Kf6 15.Kd2 Ke5 16.Kc3 Nd5+ 17.Kc4 Ne3+ 18.Kc5
= (-0.06) Depth: 25/52 00:00:20 68474kN
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 Kf7 10.Kg3 f5 11.a5 Nb4 12.Kf4 Kg6 13.g3 Kf6 14.g4 fxg4 15.Kxg4 Kg6 16.Kf4 h5 17.h4 Kf6 18.Ke4 Ke6
= (-0.07) Depth: 26/52 00:00:38 130mN, tb=3
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 f5 10.a5 Nb4 11.Kg3 Kg6 12.Kf4 Kf6 13.g3 Na6 14.g4 fxg4 15.Kxg4 Nb4 16.Kf4 Kg7 17.Ke3 Kf7 18.Kd2 Ke6 19.Kc3 Nd5+ 20.Kc4 Ne3+ 21.Kc5
= (-0.04) Depth: 27/52 00:01:09 235mN, tb=5
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 f5 10.a5 Nb4 11.Kg3 Kg6 12.Kf4 Kf6 13.g3 Ke6 14.g4 fxg4 15.hxg4 Kd5 16.g5 hxg5+ 17.Kxg5 Kc6 18.Kh5
= (-0.04) Depth: 28/55 00:02:04 419mN, tb=18
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 f5 10.g4 fxg4 11.hxg4 Kf6 12.Kg3 Kg5 13.a5 Nb4 14.Kf3 Na6 15.Kg3 Kf6 16.Kh4 Kg6 17.Kh3 Kf6 18.Kh4 Kg6
= (0.00) Depth: 29/55 00:03:04 617mN, tb=46
1...Qxa1 2.Bxe5 Qc1 3.Qg6 Rf6 4.Bxf6 Qf4+ 5.Kg1 Qxf6 6.Qxf6 gxf6 7.b3 Nd5 8.a4 Kg7 9.Kf2 f5 10.g4 fxg4 11.hxg4 Kf6 12.Kg3 Kg5 13.a5 Nb4 14.Kf3 Na6 15.Kg3 Kf6 16.Kh4 Kg6 17.Kh3 Kf6 18.Kh4 Kg6
= (0.00) Depth: 30/56 00:04:33 915mN, tb=122

[Uri Blass]

Apparently the position diagram was broken. The white queen is missing. Here is another try:

[d] 5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w - - 0 1

I saw no missing queen.

It is the same position and it seems that both Bxh6 and Bf4 draw so Bxh6 is not the only non losing move.

The diagram in YOUR post had no queen, I assumed it was the same as mine.

In any case, my original point still stands. Qxb6 looks easy at first. One does NOT want to play that move however. And later, there is another move that becomes "easy" but my current (and the suggested window approach) would not recognize a move that only looks easy as the search gets deeper..

I did not see a missing queen in the diagram in my post
and I can see both queens in all posts.

I also disagree with you that another move became easy after Qxb6 failed low.

Bxh6 is not easy unless you can be sure that it is not worse than Bf4
and both Bxh6 and Bf4 seem to lead to a draw(houdini3 showed 0.00 at depth 30 in the analysis after Bf4).

[bob]

Does it help to consider why the PV changed? I could imagine that it makes a difference whether the first move fails low (the former PV turns out to be bad/a trap, the position in the diagram) or whether another move becomes better than the PV move by itself. In the first case the move that looked good was a trap, but whatever move replaced it might still be a candidate for an "easy" move. In the second case there may be no obvious "easy" move.

Of course it may take some extra book keeping to make this distinction but it might be interesting to know the statistics at least.

Been there, tried that. Problem is that the first "best move" is not always a trap. For example, you make what appears to be a piece sac, but it is really just a very deep combination that wins the material back + a bit of positional edge. You make the sac, your opponent accepts (slightly worse than doing something else) but then it takes a DEEP search before you realize that you are not losing something. So you go thru the first N iterations thinking you are in trouble, then you find the right move and all is well. And the right move actually becomes obvious (easy) once you get deep enough.

There are so many of these different ways of changing your mind. Other options.

A fail low on the first move always triggers using more time. Until you find a new best move that is no worse score-wise. Should this be a "hard" position where you use more time anyway? As opposed to a position where you don't fail low, but do find a better move?

What about a fail high that stands for several iterations, but then goes away. Should you begin to suspect that this "apparently very good move" is maybe not so good?

That's what I am trying to uncover. Something that says move quickly, normally, or more slowly, depending on what is going on. The quickly part is not so hard, actually, and when you fail low, the slowly option is also easy enough to do, but what about positions where you have not yet failed low, but are going to. Is there a way to recognize that? I have not found one just yet...

[bob]

Apparently the position diagram was broken. The white queen is missing. Here is another try:

[d] 5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w - - 0 1

I saw no missing queen.

It is the same position and it seems that both Bxh6 and Bf4 draw so Bxh6 is not the only non losing move.

The diagram in YOUR post had no queen, I assumed it was the same as mine.

In any case, my original point still stands. Qxb6 looks easy at first. One does NOT want to play that move however. And later, there is another move that becomes "easy" but my current (and the suggested window approach) would not recognize a move that only looks easy as the search gets deeper..

I did not see a missing queen in the diagram in my post
and I can see both queens in all posts.

I also disagree with you that another move became easy after Qxb6 failed low.

Bxh6 is not easy unless you can be sure that it is not worse than Bf4
and both Bxh6 and Bf4 seem to lead to a draw(houdini3 showed 0.00 at depth 30 in the analysis after Bf4).

You can't see the forest for the trees. Forget about Bf4 and pretend it doesn't exist. Qxb6 is "easy" for a few iterations, then it fails low. Then Bxh6 is discovered to lead to a forced draw or better, and nothing else comes close. Bxh6 qualifies as "easy" here. But choose ANY position where there appears to be an easy move, until enough depth shows it to be bad, and where there is one "good move" once you get deep enough to see it... I'd like for that to be recognized as "easy" as well. And if possible (and I don't see a solution for this at all) I'd like to recognize that the original "easy" move is not "easy" before it actually fails low, because it might not fail low before my "easy move" time limit has elapsed and I make the move based on it being "easy".

[bob]

Bxh6 is not the only move that saves the position for white.
It seems that Bf4 also saves the position for white

How?

If you search it, it also leads to a draw score...

Bh6 is a little more forcing, due to the threat on g7. But clearing the back rank is the key to make the queen move.