• OptionCaveats

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Caveats for the options

Here, we document some aspects of the command-line syntax that may be unintuitive or complicated.

Setting the "cost type" for landmark heuristics

For mostly historical reasons, specifying the cost type (see HeuristicSpecification) for landmark heuristics is currently complicated. Here's the complete set of rules:

If you use the LAMA-FF synergy

There are three relevant options:

1. lm_cost_type of the landmark generation method (e.g. lm_rhw)

2. cost_type of the landmark generation method (e.g. lm_rhw)

3. cost_type of the synergy declation (lm_ff_syn)

The cost type of the synergy's landmark heuristic is determined by option 1. when using admissible=false and by option 3. when using admissible=true.

The cost type of the synergy's FF heuristic is determined by option 2.

If you do not use the LAMA-FF synergy

There are three relevant options:

1. lm_cost_type of the landmark generation method (e.g. lm_rhw)

2. cost_type of the landmark generation method (e.g. lm_rhw)

3. cost_type of the landmark heuristic declation (lmcount)

The cost type of the landmark heuristic is determined by option 1. when using admissible=false and by option 3. when using admissible=true.

Option 2 is ignored in this case.

Using preferred operators with the lmcount heuristic

Unlike all other (current) heuristics, the lmcount heuristic requires a special setting pref=true to enable preferred operator support. Hence, to use preferred operators with that heuristic, two things must be done at the moment:

1. Set pref=true in the HeuristicSpecification.

2. Include the heuristic in the list of heuristics in the preferred specification of the SearchEngine.

This does not affect the "Lama-FF synergy" version of the landmark heuristic. Using the Lama-FF synergy only makes sense when we are interested in preferred operators of the landmark heuristic, since otherwise there is no potential synergy between these heuristics. Therefore, in synergy mode the preferred operators are always computed. (Of course, they still need to be enabled in the SearchEngine as with all heuristics.)