lm-evaluation-harness is a framework that strives to support a wide range of zero- and few-shot evaluation tasks on autoregressive language models (LMs).
This documentation page provides a walkthrough to get started creating your own task, on the big-refactor branch of the repository (which will be v0.4.0 in the future.)
A more interactive tutorial is available as a Jupyter notebook here.
If you haven't already, go ahead and fork the main repo, clone it, create a branch with the name of your task, and install the project requirements in your environment:
# After forking...
git clone https://github.com/<YOUR-USERNAME>/lm-evaluation-harness.git
cd lm-evaluation-harness
git checkout big-refactor
git checkout -b <task-name>
pip install -e ".[dev]"In this document, we'll walk through the basics of implementing a static benchmark evaluation in two formats: a generative task which requires sampling text from a model, such as gsm8k, and a discriminative, or multiple choice, task where the model picks the most likely of several fixed answer choices, such as sciq.
To implement a new standard task, we'll need to write a YAML file which configures our task logic. We start by making a new empty YAML file. This file can have any name, but we recommend placing it in a subfolder of lm_eval/tasks titled by the dataset or task's shorthand name: for example,
touch lm_eval/tasks/<dataset_name>/<my_new_task_name>.yamlOr, copy the template subfolder we provide from templates/new_yaml_task:
cp -r templates/new_yaml_task lm_eval/tasks/and rename the folders and YAML file(s) as desired.
All data downloading and management is handled through the HuggingFace (HF) datasets API. So, the first thing you should do is check to see if your task's dataset is already provided in their catalog here. If it's not in there, please consider adding it to their Hub to make it accessible to a wider user base by following their new dataset guide
.
Once you have a HuggingFace dataset prepared for your task, we want to assign our new YAML to use this dataset:
dataset_path: ... # the name of the dataset on the HF Hub.
dataset_name: ... # the dataset configuration to use. Leave `null` if your dataset does not require a config to be passed. See https://huggingface.co/docs/datasets/load_hub#configurations for more info.
dataset_kwargs: null # any extra keyword arguments that should be passed to the dataset constructor, e.g. `data_dir`.Tip: To load a local dataset for evaluation, you can specify data files in the dataset_kwargs field, such as the following for JSON files:
dataset_path: json
dataset_name: null
dataset_kwargs:
data_files: /path/to/my/json
Next, we'd like to tell our task what the dataset's train, validation, and test splits are named, if they exist:
training_split: <split name of training set, or `null`>
validation_split: <split name of val. set, or `null`>
test_split: <split name of test set, or `null`>Tests will run on the test_split if it is available, and otherwise evaluate on the validation_split.
We can also specify from which split the task should retrieve few-shot examples via:
fewshot_split: <split name to draw fewshot examples from, or `null`>though if this is not set, we will default to train/validation/test sets, in that order.
Finally, our dataset may not be already in the exact format we want. Maybe we have to strip whitespace and special characters via a regex from our dataset's "question" field! Or maybe we just want to rename its columns to match a convention we'll be using for our prompts.
Let's create a python file in the directory where we're writing our YAML file:
touch lm_eval/tasks/<dataset_name>/utils.pyNow, in utils.py we'll write a function to process each split of our dataset:
TODO: Change the example to one that's in the tasks/
def process_docs(dataset: datasets.Dataset):
def _helper(doc):
# modifies the contents of a single
# document in our dataset.
doc["choices"] = [doc["choice1"], doc["choice2"], doc["wrong_answer"]]
doc["gold"] = doc["label"]
return doc
return dataset.map(_helper) # returns back a datasets.Dataset objectNow, in our YAML config file we'll use the !function constructor, and tell the config where our imported Python function will come from. At runtime, before doing anything else we will preprocess our dataset according to this function!
process_docs: !function utils.process_docsThe next thing we need to do is decide what format to use when presenting the data to the LM. This is our prompt, where we'll define both an input and output format.
To write a prompt, users will use doc_to_text, doc_to_target, and doc_to_choice (Optional when certain conditions are met).
doc_to_text defines the input string a model will be given while doc_to_target and doc_to_choice will be used to generate the target text. doc_to_target can be either a text string that refers to the target string or an integer that refers to the index of the correct label. When it is set as an index, doc_to_choice must be also be set with the appropriate list of possible choice strings.
If a dataset is straightforward enough, users can enter the feature name directly. This assumes that no preprocessing is required. For example in Swag, doc_to_text and doc_to_target given the name of one of the feature each.
doc_to_text: startphrase
doc_to_target: labelHard-coding is also possible as is the case in SciQ.
doc_to_target: 3doc_to_choice can be directly given a list of text as option (See Toxigen)
doc_to_choice: ['No', 'Yes']We support the Jinja 2 templating language for writing prompts. In practice, this means you can take your dataset's columns and do many basic string manipulations to place each document into prompted format.
Take for example the dataset super_glue/boolq. As input, we'd like to use the features passage and question and string them together so that for a a sample line doc, the model sees something the format of:
doc["passage"]
Question: doc["question"]?
Answer:
We do this by writing
doc_to_text: "{{passage}}\nQuestion: {{question}}?\nAnswer:"Such that {{passage}} will be replaced by doc["passage"] and {{question}} with doc["question"] when rendering the prompt template.
Our intended output is for the model to predict a single whitespace, and then the answer to the question. We do this via:
doc_to_target: "{{answer}}"Important: we now add target_delimiter between input and target which defaults to " ", such that the full input-output string is doc_to_target(doc) + target_delimiter + doc_to_text(doc). doc_to_text and doc_to_target should not contain trailing right or left whitespace, respectively.
For tasks which are multiple choice (a fixed, finite set of label words per each document) and evaluated via comparing loglikelihoods of all label words (the multiple_choice task output type) we enforce a particular convention on prompt format.
An annotated example in the case of SciQ is as follows:
doc_to_text: "{{support.lstrip()}}\nQuestion: {{question}}\nAnswer:" # This is the input portion of the prompt for this doc. It will have " {{choice}}" appended to it as target for each choice in answer_choices.
doc_to_target: 3 # this contains the index into the answer choice list of the correct answer.
doc_to_choice: "{{[distractor1, distractor2, distractor3, correct_answer]}}"Task implementers are thus able to decide what the answer choices should be for a document, and what prompt format to use.
The label index can also be sourced from a feature directly. For example in superglue/boolq, the label index if defined in the feature label. We can set doc_to_target as simply label. The options or verbalizers can be written in a the form of a list ["no", "yes"] that will correspond to the label index.
doc_to_text: "{{passage}}\nQuestion: {{question}}?\nAnswer:"
doc_to_target: label
doc_to_choice: ["no", "yes"]There may be cases where the prompt we want to implement is easier expressed in Python instead of Jinja 2. For this, we can use Python helper functions that are defined in the YAML config. It should be noted that the function script must be in the same directory as the yaml.
A good example is WikiText that requires a lot of regex rules to clean the samples.
def wikitext_detokenizer(doc):
string = doc["page"]
# contractions
string = string.replace("s '", "s'")
string = re.sub(r"/' [0-9]/", r"/'[0-9]/", string)
...
string = string.replace(" 's", "'s")
return string
We can load this function in doc_to_target by using a !function operator after doc_to_target and followed by <file name>.<function name>. In the file wikitext.yaml we write:
doc_to_target: !function preprocess_wikitext.wikitext_detokenizer
Promptsource is a great repository for crowdsourced prompts for many datasets. We can load these prompts easily by using the use_prompt argument and filling it with the format "promptsource:<name of prompt template>". To use this, doc_to_text and doc_to_target should be left undefined. This will fetch the template of the dataset defined in the YAML file.
For example, For Super Glue BoolQ, if we want to use the prompt template GPT-3 Style we can add this to the YAML file.
use_prompt: "promptsource:GPT-3 Style"
If you would like to run evaluation on all prompt templates, you can simply call it this way.
use_prompt: "promptsource:*"
You're almost done! Now we need to choose how to score our task.
- If this is a multiple choice task: do you just want to check your model's accuracy in choosing the correct answer choice?
- If this is a generation task: do you just want to check how often your model outputs exactly the ground-truth output string provided?
If the answer to the above is no: you'll need to record what scoring metrics to use! Metrics can be listed in the following format:
metric_list:
- metric: <name of the metric here>
aggregation: <name of the aggregation fn here>
higher_is_better: <true or false>
- metric: !function script.function
aggregation: ...
higher_is_better: ...aggregation and higher_is_better can optionally be left out to default to the manually-set defaults if using a natively supported metric, otherwise it must be defined explicitly (for example, when using a custom metric implemented as a function).
For a full list of natively supported metrics and aggregation functions see docs/advanced_task_guide.md. All metrics supported in HuggingFace Evaluate can also be used, and will be loaded if a given metric name is not one natively supported in lm-eval or hf_evaluate is set to true.
Some tasks may require more advanced processing logic than is described in this guide.
As a heuristic check:
- Does your task require generating multiple free-form outputs per input document?
- Does your task require complex, multi-step post-processing of generated model outputs?
- Does your task require subsetting documents on the fly based on their content?
- Do you expect to compute metrics after applying multiple such processing steps on your model outputs?
- Does your task rely on metrics that need a custom implementation?
For more detail on the task system and advanced features, see docs/advanced_task_guide.md . If none of the above sound like they apply to your task, it's time to continue onto checking your task performance!
To test a task conveniently, it helps to register the task--that is, to give it a name and make the lm-eval library aware it exists!
If you're writing your YAML file inside the lm_eval/tasks folder, you just need to give your task a name! You can do this inside your YAML file:
task: <name of the task>Including a task name is mandatory.
It is often also convenient to label your task with several groups, or tags, though this field is optional:
group:
- group1
- group2This will add your task to the group1 and group2 groups, enabling people to know how to categorize your task, and if desired run all tasks in one of these groups at once, your task along with them.
If your task is not in the lm_eval/tasks folder, you'll need to tell the Eval Harness where to look for YAML files.
You can do this via adding the Python snippet
from lm_eval.tasks import include_task_folder
include_task_folder("/path/to/yaml/parent/folder")to the top of any Python file that is run or imported when performing evaluation, such as \_\_main\_\_.py.
Passing --tasks /path/to/yaml/file is also accepted.
To avoid conflict, each task needs to be registered with a unique name. Because of this, slight variations of task are still counted as unique tasks and need to be named uniquely. This could be done by appending an additional naming that may refer to the variation such as in MMLU where the template used to evaluated for flan are differentiated from the default by the prefix mmlu_flan_*. Printing the full task names can easily clutter the results table at the end of the evaluation especially when you have a long list of tasks or are using a benchmark that comprises of many tasks. To make it more legible, you can use task_alias and group_alias to provide an alternative task name and group name that will be printed.
``
for example in mmlu_abstract_algebra.yaml we set `group_alias` to `stem` and `task_alias` to `abstract_algebra`.
"dataset_name": "abstract_algebra"
"description": "The following are multiple choice questions (with answers) about abstract\
\ algebra.\n\n"
"group": "mmlu_stem"
"group_alias": "stem"
"include": "_default_template_yaml"
"task": "mmlu_abstract_algebra"
"task_alias": "abstract_algebra"
Note: Even though group can be a list, for now, group_alias can only be a single string.
After registering your task, you can now check on your data downloading and verify that the few-shot samples look as intended. Run the following command with your desired args:
python -m scripts.write_out \
--output_base_path <path> \
--tasks <your-task-name> \
--sets <train | val | test> \
--num_fewshot K \
--num_examples N \Open the file specified at the --output_base_path <path> and ensure it passes
a simple eye test.
It's now time to check models' performance on your task! In the evaluation harness, we intend to support a wide range of evaluation tasks and setups, but prioritize the inclusion of already-proven benchmarks following the precise evaluation setups in the literature where possible.
To enable this, we provide a checklist that should be completed when contributing a new task, to enable accurate book-keeping and to ensure that tasks added to the library are well-tested and, where applicable, precedented.
The checklist is the following:
For adding novel benchmarks/datasets to the library:
- Is the task an existing benchmark in the literature?
- Have you referenced the original paper that introduced the task?
- If yes, does the original paper provide a reference implementation? If so, have you checked against the reference implementation and documented how to run such a test?
If other tasks on this dataset are already supported:
- Is the "Main" variant of this task clearly denoted?
- Have you provided a short sentence in a README on what each new variant adds / evaluates?
- Have you noted which, if any, published evaluation setups are matched by this variant?
It is recommended to include a filled-out copy of this checklist in the README.md for the subfolder you are creating, if you have created a new subfolder in lm_eval/tasks.
You're all set! Now push your work and make a pull request to the big-refactor branch! Thanks for the contribution :). If there are any questions, please leave a message in the #lm-thunderdome channel on the EAI discord!