translate

SAS-based Translator for FOND domains

This repo contains a minor variant of the original SAS-based translator shipped with downard for planning domains that are determinizations of FOND planning task (for example via fond-utils).

Important

Current SAS translator version: commit 113fe1a for release 24.06 - June 2024.

The main script is translate.py, which requires both domain and problem instance:

$ python translate.py problems/blocksworld-ipc08/domain.pddl problems/blocksworld-ipc08/p01.pddl

By default, it generates a file output.sas with the SAS encoding of the determinization of the original non-deterministic problem. An alternative SAS filename can be given via --sas-file option.

The only difference with the original translator is that it does not drop operators resulting from all-outcome determnization; see below for more explanation.

Warning

This translator does not accept FOND planning domains, it has to be deterministic planning problems (but these would typically be determinizations of original FOND domains!).

Changes to original SAS translator

The only difference with the original translator is that this version does not simplify operators that are the result of FOND determinization. The original translator will drop an action if it is not useful ot the goal in the problem instance, for example, if it is a no-op action. However, a no-op action that corresponds to one of the effects of a non-deterministic operator should indeed be taken into account when performing FOND planning.

So, this translator will keep any operator whose name contains the string DETUP, which signals that is an action corresponding to one of the many oneof effects of the original non-deterministic action.

All the changes were documented with the string # CHANGE FOND and affect the following giles:

$ diff -qr translate translate-fond -x '__pycache__'
Files translate/pddl/actions.py and translate-fond/pddl/actions.py differ
Files translate/pddl_parser/parsing_functions.py and translate-fond/pddl_parser/parsing_functions.py differ
Files translate/simplify.py and translate-fond/simplify.py differ
Files translate/translate.py and translate-fond/translate.py differ
Files translate/variable_order.py and translate-fond/variable_order.py differ

Update workflow

From time to time, the SAS translator is updated and improved and we may want to bring those changes to the FOND version. To do so:

1. Get the new src/translate folder from downward. Maybe save the release under ../../.

2. The new downward release may or may not have updated the translator wrt the current version. If no changes were done on the translator, nothing else needs to be done, the current translator here is up to date. To check, you can use meld or diff:

   $ meld ../original-translators/downward-release-24.06.0/src/translate translate/

3. Otherwise, using diff and mend and the documented changes above, build an updated translator under translate/ folder here. Dependign how much the translator changed, this may require manual work. 😲

4. Produce the patch file that can be used to patch the original translator:

   $ diff -crB -x "__pycache__" translate translate-fond > translate-fond-3c8a65b.patch

5. Push the changes to the remote, including the patch!

Apply the patch

To modify the original translator with the FOND features (assuming the original translator is in translate/ folder):

$ patch --directory=translate --strip=1 < /path/to/patch/translate-fond-3c8a65b.patch
patching file pddl/actions.py
patching file pddl_parser/parsing_functions.py
patching file simplify.py
patching file translate.py
patching file variable_order.py

# check!
$ grep -r "FOND" translate
translate/variable_order.py:            # CHANGE FOND: return ND-action even if effect is empty!
translate/translate.py:    # CHANGE FOND?: unclear if this is needed, when will be empty? what is condition?
translate/translate.py:    # CHANGE FOND: we want to keep all ND actions, even if they have no effects
translate/simplify.py:        # CHANGE FOND: do not remove ND operators with empty effect
translate/pddl_parser/parsing_functions.py:    # CHANGE FOND: keep actions with empty effects
translate/pddl/actions.py:        # CHANGE FOND: return ND-action even if effect is empty!

Contributors

The codebase is a modification/extension of the translators found in Downard library (which ships the SAS translation).

• Sebastian Sardina (ssardina@gmail.com)
• Nitin Yadav (nitin.yadav@unimelb.edu.au)