An additional reduction rule has been added to the BlockLayout package (version 6.9.27) to help reduce so-called ‘rigids’. The image below shows the idea.
The two blue arcs are removed by the reduction rule, the two red arcs and three new blocks are added by it:
- A dummy block u’ for u. This block has identical size as the block of u, and is there to prevent t from being too close to p.
- A similar dummy block x’ for x, to prevent t from being too close to s.
- A horizontal block containing both dummy blocks and the block of t. This horizontal block will be the new block attached to t.
Note that places q and r are not allowed to have additional inputs or outputs. Also note that t is conveniently drawn in the middle, but that vertical blocks are sorted in the Block Layout. As a result, in the end, block t may be positioned ‘out of the middle’.
The following images shows the results on net 2 of the PDC 2019, both with and without using this new rule.