## Sunday, September 02, 2012

### Preliminary tactics

When I thought for the first time about the preparation of tactics, I thought that there would be a whole new area ready to be explored.
But the analysis of the game that lead to a combination in the previous post forced me to write the following conclusion down:
• Make sound moves based on simple positional considerations.
• Have a keen eye for the consequences of the moves of your opponent.
In other words: nothing new under the sun and don't forget to look for the seeds of tactical destruction.

Before I can archive this conclusion as definite, there are a few loose ends that must be tidied up.
I don't know beforehand what I'm going to write, or whereto it will lead, if anywhere, so please have a little patience with me.

Is there really nothing that you can do that encourages your opponent to jump into the abyss himself?

I analyzed the game with the aid of Houdini. That shows a more or less balanced game until black made a blunder at move 22. The gradual manifestation of the tactical elements that constituted the final combination seems not to be reflected in the figures of Houdini. So I looked a bit closer at these figures.

With Houdini I can set the multi pv (principled variation) to 16. This means that I get per move the 16 best candidates with their score. I wanted to see if the tactical elements had an influence on the amount of candidate moves that change the game in a negative way. In other words: do you have less good choices when tactical elements build up? Do they influence the chance to blunder?
I divided the candidate moves in 3 classes:
• > - 0.40 I deemed the moves as not loosing
• - 0.40 > x > - 1.0 I deemed as critical
• < - 1.0 I deemed as loosing
It's rather arbitrary, but it's just to get an idea.

Move
best
white
pawn points
good
white
#candidates
critical
white
#candidates
loosing
white
#candidates
best
black
pawn points
good
black
#candidates
critical
black
#candidates
loosing
black
#candidates
1
+0.15
16

-0.15
11
5

2
+0.24
16

-0.27
4
12

3
+0.28
16

-0.19
10
6

4
+0.32
16

-0.12
16

5
+0.14
16

-0.11
16

6
+0.12
16

-0.10
16

7
+0.15
16

-0.04
16

8
+0.10
16

+0.02
16

9
+0.39
16

-0.38
3
13

10
+0.65
16

-0.37
1
2
13
11
+0.40
16

-0.24
1

3
12
+0.24
16

+0.07
13
3

13
-0.10
4
4
8
+0.26
16

14
-0.28
2
13
1
+0.27
16

15
-0.24
1

15
+0.27
10
6

16
-0.44

10
6
+0.50
2
2
12
17
-0.46

16

+0.54
16

18
-0.34
2
5
9
+0.38
14
1
1
19
-0.40
1

15
+0.17
8
4
4
20
-0.18
2
3
11
+0.41
1
1
1
21
-0.41

3
13
+0.24
16

22
+0.94
5
2
9
0.00
6
3
7
23
+4.20
6
10

-5.39

3
24
+4.70
1

15
-4.84

3
25
+5.81
1

15
-5.28

16
26
+5.26
16

-5.65

1
27
+5.54
15
1

-5.75

3

Before the first tactical element is put into place at move 9, it is impossible for black to make a loosing blunder. To be correct I must add: when he plays 1 of the 16 best candidates. But for convenience I leave that away.

It gives an idea how forcing a move is. If your bishop is taken, you probably must take it back or you loose.  The best move is the best they could have played according to Houdini. The good, the critical and the loosing moves should add up to 16. Since that is the max amount of multi pv that Houdini can handle. Some times they don't add up to 16. That happens when there are less than 16 legal moves. Usually when the king is in check.

The positional elements are implemented by the evaluation function of the chess engine.
This works with a bonus/penalty system. A knight at a1 gets a penalty while a knight on e5 gets a bonus.

The tactical elements are scored in a more implicit way. The computer looks into the future and counts the material on the board.

Let's have a look at the tactical elements from the previous post.
I will try to divide them into two categories, one is scored by the positional part of evaluation function of the engine while the other  category is tactical.

Positional, based on the bonus/penalty system of the engine:
• 9. ... f5 {At this moment the diagonal a2 - g8 is weakened}
• 10. dxe5 {After the pawn exchange the d-file is half open}
• 10. ... dxe5 {After the pawn exchange the d-file is open}
• 11. Bc4 {Occuppying the diagonal with tempo}
• 13. ... Ne7 {Putting the knight in a position where it becomes clumsy.}
• 14. ... c6 {Weakens d6. Gives white the opportunity to pressurize the d-file. Leads to overload of Rf8. Furthermore it frustrates the development of Bc8, which makes the backrank weak since the rooks cannot connect}
• 16. Rad1 {Occupying the d-file}
• 18. ... Nxg5 {Gives the white knight the opportunity to occupy d6 with tempo}
Tactical, based on material count within the horizon of the engine:
• 16. ... Qc7 {Putting the Queen on a knight’s jump distance to the rook}
• 20. ... Kg7 {Binding the king to the defence of f7, which is at knightforks distance from Qc7}
• 22. Qc4 {Putting the front end of the battery in place} a6 {Gives the opportunity to launch the combination}
The moves of the positional category you can find by "old school" positional considerations.
What can we say about the tactical category?

The category can be divided in a passive and an active section.
Passive means that your opponent makes the move and you have to be keen on its potential tactical consequences. moves 16 and 20 fall into this section. If I generalize this, it states "look out for the seeds of tactical destruction".
Active means that you can make a move that puts a tactical element into place. Move 22 is an example. Since you are not allowed to move the pieces of your opponent, we talk about the placement of your attackers here.

You can place your attackers based on general considerations and based on specific considerations.
If you place your attackers based on general considerations, you make essentially a positional move. Occupy an outpost. Occupy an open file etc..

If I summarize the previous deliberations till sofar we may finally get some focus (I told you to be patient):
If there exists something like prelimanary tactics we have to look in an area with the following characteristics:
• Attacker placement (since you are only allowed to move your own pieces).
• Based on specific considerations (otherwise it would be positional).
• Non forcing (otherwise it would be a mature tactic).
I wil investigate this further in a following post.
To be continued. . .