Re: [gnugo-devel] dfa_unsort_1_25.1

[Inge Wallin]

Arend wrote:
> For example
> 
> XX
> ..
> XX
> 
> should be evaluated before
> 
> X
> .
> X
> 
> to avoid a heavy connection test.

A long time ago, I proposed a keyword 'supercedes' for patterns.
Consider the two patterns above (never mind pattern syntax here):

Pattern C1

XX
..
XX
 
:supercedes(C2)

Pattern C2

X
.
X

This would mean that pattern C2 would never even be tried if C1
matches.  I think that we could easily gain a lot of nodes here since
we could easily create special case patterns for common, but expensive
reading cases.

I don't think it would be very difficult to implement either in the
old pattern matcher.  In the case of the DFA, I think that we would
have to collect all patterns that match and then before checking
constraints sort them and see if one pattern supercedes another.
Maybe this sorting is already done, I don't know.

        -Inge