Difference between revisions of "Bolstered template"

From HexWiki
Jump to: navigation, search
(New article on bolstered templates.)
 
m (Minor edits and typos.)
 
Line 80: Line 80:
 
   contents="R b1 a3 E x:a2 y:b2 R b3"
 
   contents="R b1 a3 E x:a2 y:b2 R b3"
 
   />
 
   />
then Blue should never try to intrude at y. Blue may still try to intrude at x. If the bridge is bolstered on the left, the situation is of course reversed. Finally, if a bridge is bolstered on both sides, for example like this
+
then Blue should never try to intrude at y. Blue may still try to intrude at x. If the bridge is bolstered on the left, the situation is reversed. Finally, if a bridge is bolstered on both sides, for example like this
 
<hexboard size="3x4"
 
<hexboard size="3x4"
 
   coords="none"
 
   coords="none"
Line 119: Line 119:
 
   contents="R a1 a3 b3 c1 E *:c2 B d2"
 
   contents="R a1 a3 b3 c1 E *:c2 B d2"
 
   />
 
   />
then Blue cannot gain anything by intruding at "*". In face, in this case, the entire carrier of the trapezoid is [[captured cell|captured]]. Of course, since the trapezoid contains a bridge, this is actually a special case of a bridge bolstered on both sides.
+
then Blue cannot gain anything by intruding at "*". In fact, in this case, the entire carrier of the trapezoid is [[captured cell|captured]]. Of course, since the trapezoid contains a bridge, this is actually a special case of a bridge bolstered on both sides.
  
 
=== In a game ===
 
=== In a game ===

Latest revision as of 11:41, 6 May 2022

Many templates have one or more intrusion points of this shape:

AxBC

Here, the cells x and "*" are empty and are part of the template's carrier. The shaded cells A, B, and C are outside of the template's carrier and may or may not be empty. The cell "*" is the intrusion point in question; we call it an exposed intrusion point.

We say that the template (or more specifically, the intrusion point "*") is bolstered if A is occupied by Red, B is occupied by Blue, and/or C is occupied by Red. In other words, there are 3 ways to bolster it:

    
Ax
    
xB
    
xC

The point is that it is never a good idea for Blue to intrude at a bolstered intrusion point. Because if Blue attempts to do so, Red can simply choose to respond at x, killing Blue's stone. This never improves Blue's position, and often makes it worse.

    
A21
    
21B
    
21C

Examples

Bolstered bridge

A bridge has two exposed intrusion points, here labelled x and y:

xy

In general, Blue may intrude either at x or at y, hoping to gain some territory on the left or right side of the bridge, respectively. However, if the bridge is bolstered on the right:

    
xy
    
xy
    
xy

then Blue should never try to intrude at y. Blue may still try to intrude at x. If the bridge is bolstered on the left, the situation is reversed. Finally, if a bridge is bolstered on both sides, for example like this

xy

or like this:

xy

then Blue cannot gain anything by intruding at x nor at y; in this case, x and y are already captured by Red.

Bolstered trapezoid

The trapezoid has one exposed intrusion point:

However, if the trapezoid is bolstered, for example like this

or like this:

then Blue cannot gain anything by intruding at "*". In fact, in this case, the entire carrier of the trapezoid is captured. Of course, since the trapezoid contains a bridge, this is actually a special case of a bridge bolstered on both sides.

In a game

Consider the following position, with Blue to move:

abcdefghijk1234567891011xy

If Blue wants to intrude in the highlighted bridge, should Blue intrude at x or at y? The answer is: Blue should intrude at y (or not at all). This is because the bridge is bolstered on the left. As a matter of fact, in this position, y is winning for Blue, whereas x is losing.

abcdefghijk123456789101152143