clingexplaid 1.0.9

A template project.

clingexplaid

Usage

Run the following for basic usage information:

clingexplaid -h

The clingexplaid CLI (based on the clingo.Application class) can be called using this generic command.

clingexplaid <filenames> <n> <method> <options>

• <filenames>: has to be replaced by a list of all files or a single filename
• <n>: defines how many models are computed (Default=1, All=0)
• <method>: specifies which Clingexplaid method is used (Required)
  • Options:
    • --muc:
      • Computes the Minimal Unsatisfiable Cores (MUCs) of the provided unsatisfiable program
    • --unsat-constraints:
      • Computes the Unsatisfiable Constraints of the unsatisfiable program provided.
    • --show-decisions:
      • Visualizes the decision process of clasp
• <options>: Additional options for the different methods
  • For --muc:
    • -a, --assumption-signature: limits which facts of the current program are converted to choices/assumptions for finding the MUCs (Default: all facts are converted)
  • For --show-decisions:
    • --decision-signature: limits which decisions are shown in the visualization (Default: all atom's decisions are shown)

Examples

• A selection of examples can be found here

Development

Installation

To install the project, run

pip install .

To improve code quality, we run linters, type checkers, and unit tests. The tools can be run using nox. We recommend installing nox using pipx to have it available globally:

python -m pip install pipx
python -m pipx install nox
nox

You can invoke nox -s to run individual sessions. For example, to install your package into a virtual environment and run your test suite, invoke:

nox -s test

We also provide a nox session that creates an environment for development. The project is installed in editable mode into this environment along with linting, type checking and formatting tools. Activating it allows your editor of choice to access these tools for, e.g., linting and autocompletion. To create and then activate virtual environment run:

nox -s dev
source .nox/dev/bin/activate

Furthermore, we provide individual sessions to easily run linting, type checking and formatting via nox. These also create editable installs. So you can safely skip the recreation of the virtual environment and reinstallation of your package in subsequent runs by passing the -R command line argument. For example, to auto-format your code using black, run:

nox -Rs format -- check
nox -Rs format

The former command allows you to inspect changes before applying them.

Note that editable installs have some caveats. In case there are issues, try recreating environments by dropping the -R option. If your project is incompatible with editable installs, adjust the noxfile.py to disable them.

We also provide a pre-commit config to automate this process. It can be set up using the following commands:

python -m pipx install pre-commit
pre-commit install

This blackens the source code whenever git commit is used.

Problems and Limitations

Meta-encoding based approach (ASP-Approach)

Important Notes:

• The Meta-encoding approach as it stands is not fully functional

Problem:

• In the meta encoding all facts (or a selection matching a certain signature) are transformed into assumptions which are then used as the assumption set for finding the MUC
• During the MUC search when subsets of this assumption set are fixed for satisfiability checking it is important that even though they are not fixed, the other assumptions are not assumed as false but as undefined
• This is currently not possible with the meta-encoding, since assumptions are chosen through a choice rule and all assumptions that aren't selected are defaulted to false
• This doesn't allow for properly checking if such subsets entail unsatisfiability and thus prevents us from finding the proper MUCs

Specifying Assumption Set using only Signatures

Important Notes:

• clingo-explaid provides the --muc mode which gives you Minimal Unsatisfiable Cores for a given set of assumption signatures that can be defined with -a
• These signatures though allow not always for finding the best fitting MUC for a given encoding, compared to an assumption set generated by hand

Problem:

• Imagine this example encoding:

a(1..3).
:- a(X).

unsat.
:- unsat.

• So when I execute clingexplaid examples/misc/bad_mucs.lp --muc 0 I get the MUCs:

MUC 1
a(3)
MUC 2
a(2)
MUC 3
a(1)
MUC 4
unsat

• So you would generally expect that executing clingexplaid examples/misc/bad_mucs.lp --muc 0 -a/1 would return the first 3 found MUCs from before
• But what actually happens is that there are no MUCs detected:

NO MUCS CONTAINED: The unsatisfiability of this program is not induced by the provided assumptions
UNSATISFIABLE

• This is actually due to an implicit (unsat, False) in the first 3 MUCs that isn't printed
• Since the standard mode of --muc converts all facts to choices when no -a is provided a(1), a(2), a(3), and unsat are all converted to choices
• We know that for the program to become satisfiable unsat cannot be true (line 4)
• But since it is provided as a fact the choice rule conversion is necessary for the iterative deletion algorithm to find any MUCs
• This holds vice versa for the last MUC 4 just so that all a/1 need to be converted to choice rules for the MUC to be found