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Subject: Re: All shortest paths & other flood-fill based algorithms

Author: Steffan Westcott

Date: 05:48:36 09/14/02

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On September 14, 2002 at 04:33:22, Gerd Isenberg wrote:

>So if you found a asp-bitboard with only one bit set, you really found a
>bottleneck - great.


Gerd,

This is not true. To locate bottlenecks, you must consider all paths, not just
the shortest ones. This fact means a square may have several path lengths
leading to it, so we can't use the ideas in AllShortestPaths().

However, if we define a bottleneck to be a square (or several squares) that all
valid paths must go through, then we have a simple test for a proposed
bottleneck :

---- CUT HERE ----

bool IsBottleneck(BitBoard sq1, BitBoard sq2, BitBoard mask,
                  BitBoard bottleneck)
{
    return !SquaresAreConnected(sq1, sq2, mask & ~bottleneck);
}

---- CUT HERE ----

ie. we constrict the mask and test if all the valid paths break.

Cheers,
Steffan



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