Monday, August 28, 2006

1152 Basic Pin Patterns

After my first expedition into the pattern jungle and the encouragements of my fellow Knights I am kind of frightened about my own courage. I fear to get lost in the jungle, ending up with a lot of work without any useful results.

Before doing more such expeditions I need a kind of map. The first pattern to map are the pins, for various reasons. Weeks and months ago I missed pins at CTS over and over again. Then I becan to focus on pins. I got the pins on files quickly, but still missed diagonal pins. I focused on diagonal pins and missed pins on ranks. Therefore, the first and most important feature of a pin must be its direction. Here is my classification of pins (the actors are Pinner-Pinnee-Target):
  1. Direction: Files, Ranks, Diagonals (3 possibilities)
  2. Degree: absolute (Target=King), relative (2 possibilities)
  3. Pinner-Pinnee-Relation: Pinnee may capture or may not capture pinner (2 possibilities)
  4. Pinnee Value: Pinnee is of higher, of equal or lesser value than pinner (3 possibilities)
  5. Pinnee Exposition: unprotected, not sufficiently protected and may be once more attacked, protected but may be further attacked by a piece of lesser value, sufficiently protected (4 possibilities)
  6. Creation of the pin: unforced (pre-existing), pulling the target into the pin by a sacrifice or by a capture-recapture sequence, pushing the target into the pin by a threat or by a check, pulling the pinnee by a sacrifice or by a capture-recapture sequence, pushing the pinnee by a threat (8 possibilities)
So there must be at least 3x2x2x3x4x8 = 1152 basic pin patterns.

Wow, I definitely must have underestimated the number of basic patterns when pins alone make such a huge number. And no wonder I used to miss so many pins earlier. Of course the number of basic pins is too large to store them all in the memory. But the pin features or, as they could be called, dimensions should be stored there for a quick retrieval.


At 1:23 AM, Blogger King of the Spill said...

>a lot of work without any useful results.

That is an extremely common self assessment for chess players. Your post really clarifies how these pins show up, and reviewing that can't hurt!


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