BOHR
----------------------------------
Big Old Heuristic Repository



.. contents:: **Contents**
  :backlinks: none

Getting started with BOHR
===========================================

Python >= 3.8 is required, preferably use virtual environment.

#. Run ``git clone https://github.com/giganticode/bohr && cd bohr``
#. Install BOHR framework library: ``chmod +x bin/setup-bohr.sh && bin/setup-bohr.sh``. This will install `bohr-framework <https://github.com/giganticode/bohr-framework>`, dependencies and tools to run heursistics.

Downloading datasets and models
===============================

#. Run ``bohr repro``

Bohr extensively uses `DVC (Data Version Control) <https://dvc.org/>`_ to ensure of the datasets and models.

Contributing to BOHR:
=====================


1. Heuristics:
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Heuristics can be found in ``.py`` files in the ``bohr/heuristics`` directory, and are marked with @Heuristic decorator. Example:

.. code-block:: python
 
    @Heuristic(Commit)
    def bugless_if_many_files_changes(commit: Commit) -> Optional[Labels]:
        if len(commit.files) > 6:
            return CommitLabel.NonBugFix
        else:
            return None
            
Important things to note:

#. Any function becomes a heuristic once it is marked with ``@Heuristic`` decorator
#. Artifact type is passed to heuristic decorator as a parameter; method accepts an object of artifact type
#. Method name can be arbitrary as long it is unique and descriptive
#. Method should return ``label`` if a datapoint should be labeled with ``label``, ``None`` if the labeling function should abstain on the datapoint

Please refer to the `documentation <https://giganticode.github.io/bohr/Heuristics.html>`_ for more information on heuristics and special heuristic types.        

2. New tasks:
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tasks are defined in the `bohr.json` file. Below you can see an example of "bugginess" task.

.. code-block:: json

   "bugginess": {
      "top_artifact": "bohr.artifacts.commit.Commit",
      "label_categories": [
        "CommitLabel.NonBugFix",
        "CommitLabel.BugFix"
      ],
      "test_datasets": [
        "datasets.1151-commits",
        "datasets.berger",
        "datasets.herzig"
      ],
      "train_datasets": [
        "datasets.bugginess-train"
      ],
      "label_column_name": "bug"
    }



The name of the task is the key in the dictionary. The value is an object with the following fields:

#. **Top artifact** - the artifact to be catigorized. In the case of "bugginess" task, commits are classified, therefore the top artifact is ``bohr.artifacts.commit.Commit``;
#. **Label categories** - categories artifact to be classified as, for "bugginess" taks these are *CommitLabel.BugFix* and *CommitLabel.NonBugFix*. Values has to be taken from the ``labels.py`` file. See section `3. Labels:`_ on more information about labels in bohr and how to extend the label hierarchy.
#. **Training sets** - datasets used to train a label model;
#. **Test sets** - datasets to calculate metrics on.

3. Labels:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Labels that are used to label artifacts in BOHR are pre-defined and can be reused across multiple tasks. E.g., ``Commit.Refactoring`` label can be used in heuristics for the tasks of detecting refactoring, but also in the task of detecting bug-fixing commits. Moreover, labels are organized in a hierarchy, e.g. ``Commit.FileRenaming`` can be a child of ``Commit.Refactoring``. Formally speaking, there is a binary relation IS-A defined on the set of labels, which defines their partial order, e.g. ``IS-A(Commit.FileRenaming, Commit.Refactoring)``           

Labels are defined in text files in the ``bohr/labels`` dir. Each row has a format: <parent>: <list of children>. Running ``bohr parse-labels`` will generate `labels.py` file in the root of the repository. Thus to extend the hierarchy of labels it's sufficient to make a change to a text file. The `label.py` will be regenerated, once the PR is received.

4. Datasets
~~~~~~~~~~~~~~~~~~~~~~~~~~~

A datasets are added by creating a dataset file in ``datasets`` folder. The name of the file will correspond to the name of the dataset. e.g.:

*datasets/1151-commits.py*:

.. code-block:: python

  from pathlib import Path

  from bohr.templates.dataloaders.from_csv import CsvDatasetLoader
  from bohr.templates.datamappers.commit import CommitMapper

  dataset_loader = CsvDatasetLoader(
      path_to_file="data/bugginess/test/1151-commits.csv",
      mapper=CommitMapper(Path(__file__).parent.parent),
      test_set=True,
  )

  __all__ = [dataset_loader]
  
In this file, an instance of ``CsvDatasetLoader`` object is created, which is added to the __all__ list (important!)

Dataloader can be an instance of custom ``DatasetLoader`` implementing the following interface:

.. code-block:: python

  @dataclass
  class DatasetLoader(ABC):
    test_set: bool
    mapper: ArtifactMapper
    
    @abstractmethod
    def load(self, project_root: Path) -> DataFrame:
        pass

    @abstractmethod
    def get_paths(self, project_root: Path) -> List[Path]:
        pass
        
*ArtifactMapper* object that has to be passed to the ``DatasetLoader`` defines how each datapoint is mapped to an artifact object and has to implement the following interface:

.. code-block:: python

  class ArtifactMapper(BaseMapper, ABC):
      @abstractmethod
      def __call__(self, x: DataPoint) -> Artifact:
          pass
          
      @abstractmethod
      def get_artifact(self) -> Type[Artifact]:
          pass
          
``bohr.templates.datamappers`` in the bohr-framework lib provide some predefined mappers.

5 Artifact definitions
~~~~~~~~~~~~~~~~~~~~~~~~
``bohr.templates.artifacts`` also defines some pre-defined artifacts


Contribute to the framework:
=============================

To contribute to the framework, please refer to the documentation in the  the `bohr-framework <https://github.com/giganticode/bohr-framework>`_ repo.


Pre-prints and publications
===========================================

.. code-block::

  @misc{babii2021mining,
        title={Mining Software Repositories with a Collaborative Heuristic Repository}, 
        author={Hlib Babii and Julian Aron Prenner and Laurin Stricker and Anjan Karmakar and Andrea Janes and Romain Robbes},
        year={2021},
        eprint={2103.01722},
        archivePrefix={arXiv},
        primaryClass={cs.SE}
  }