Before we write a computer program with a goal of playing
a strong positional game of chess, we should first look at some texts on the subject of playing positional chess - we should
understand how chess experts teach the concepts.
p.5"Thanks for picking this book up. I'm sure that with careful
study it will help you understand the intricacies of positional chess much better and guide you to making better decisions
throughout the course of all your games."
Here is Hansen's definition of Positional Chess:
p.6"What is Positional Chess? Let's start out by defining what we are about to discuss in this book.
Positional chess refers to all the elements in chess that go into the evaluation of a position, and into the assessment of
which plan and strategy is best in a given position."
Hansen argues that 90% of chess is based on positional factors. All the more reason to understand
and identify these factors. We will then begin to think about how to write heuristics which use them in the evaluation
function of our program.
p.7"I think that chess is at least 90% based on positional factors."
Hansen claims that positional chess begins with understanding imbalances in a given position.
p.9"Imbalances are the factors in any given position that determine who is better, who has the initiative
and who can play for the win. The better you learn to understand imbalances and to evaluate how they balance out, the better
you will become as a chess-player."
King safely is important to playing a positional game of chess:
p.9"when assessing king safety in the flow of a game, just ask yourself how the last move influenced
the situation of the king."
Using pattern matching to play a positional game of chess is likely to fail because similar positions
can have different evaluations. There is nothing wrong with using a pattern to guide our search, but to form a concrete evaluation
based on a specific pattern is likely to be inaccurate.
p.13"In my opinion, imbalances which are based on piece coordination and piece placement can be
very difficult to assess. In some instances, such imbalances seem to favour one side entirely, while in an apparently very
similar position, it may turn out to be the other way around."
Mobility allows pieces to threaten to accomplish multiple objectives, often on different sides of
the board.
p.20"what is piece mobility? It is the ability to move the pieces more freely to relevant squares...
Better piece mobility makes it possible to take advantage of those fleeting moments when an opportunity arises in one or more
spots on the board and your pieces can readily switch from their current roles to taking advantage of those kinds of opportunities."
Strong players can recognize and exploit small weaknesses. A chess program that plays a positional
game of chess must also be able to do this.
p.29"as players become stronger, and the more experience they gain,
they become adept at detecting even the smallest and apparently insignificant weaknesses... a weakness is only a weakness
if there is a realistic possibility that the opponent can exploit it in one way or another."
Weak squares are the most common form of weakness. Perhaps our heuristic should be sensitive to
recognizing this feature.
p.31"Weak Squares: This is the most common type of weakness."
Most amateurs do not recognize a weak color complex. Does the detection and exploitation of this
feature have a performance payoff?
p.35"Weak Colour Complex... The remarkable thing is that this type of weakness occurs relatively
often, yet it is often left unexploited by inexperienced players who fail to notice it."
Weak pieces should be identified by our positional evaluation function. We should think about a
heuristic which measures how "engaged" a piece is in the battle.
p.40"Weak Pieces...It can more or less be any piece that is isolated from the action or from its
fellow pieces, but is more often than not a minor piece."
Hansen points out that open files are useful only if an entry point exists for a piece to penetrate
into the opponent's position. If we give points to pieces for sitting on open files without checking for entry points (like
traditional chess programs) we might be focusing our search efforts incorrectly.
p.66"An open file is only useful if there are weaknesses or entry-squares
on the file or in connection with the file."
What if our chess program could accurately evaluate the positional consequences of an exchange sacrifice?
It might have an opportunity to attack or defend that a traditional chess program would not consider. This might lead to better
overall performance in terms of wins/ draws/ losses.
p.80"A very effective way of creating an imbalance is the use of the exchange sacrifice. It can
be used in several different ways, both aggressively and defensively. Understanding how and when to use it effectively means
the addition of a very powerful weapon in your amoury."
For a human to successfully play a positional game of chess, it seems that one needs to study
the basic types of weaknesses, play through grandmaster games where they are demonstrated/ exploited, and know how to
trade one type for another type. Once again, Carsten Hansen hints that a weakness is not truly a weakness if it cannot be
exploited by your opponent. One begins to wonder about the accuracy of traditional chess programs that award points for
doubled and isolated pawns without first checking the exploitability of these structures.
p.110"One of the keys to successful positional play is to understand the impact of structural weaknesses
[isolated pawns, backward and hanging pawns, doubled pawns, fixed pawns, weak squares, weak color complexes, diagonals, open
files, majorities/minorities, overextended structures, lack of space, passivity, etc.]. These come in all shapes and sizes,
and knowing how to identify them and exploit them is a major difference between stronger and weaker players."
Pawn sacrifices for positional reasons play a part in many high-level games. Our chess program
should be able to accurately calculate the positional consequences of such sacrifices, and take advantage of these opportunities
when they arise.
p.131"Like it or not, pawn sacrifices are a natural and important part of positional chess... The
point is that the sooner you start realizing the importance of understanding material imbalances as positional imbalances
[these subtopics are then discussed: pawn for imbalance, damaging the opponent's pawn structure, damaging the opponent's coordination,
sacrifice to gain time, sacrifice to win the initiative, making way, room to breathe], the sooner your level of chess will
improve."
