---
title: DmxPerplexity
emoji: 🌖
colorFrom: purple
colorTo: pink
sdk: gradio
sdk_version: 4.7.1
app_file: app.py
pinned: false
license: apache-2.0
tags:
- evaluate
- metric
description: >-
  Perplexity metric implemented by d-Matrix.
  Perplexity (PPL) is one of the most common metrics for evaluating language models.
  It is defined as the exponentiated average negative log-likelihood of a sequence, calculated with exponent base `e`.
  Note that this metric is intended for Causual Language Models, the perplexity calculation is only correct if model uses Cross Entropy Loss.
  For more information, see https://huggingface.co/docs/transformers/perplexity
---

# Metric Card for Perplexity


## Metric Description

Perplexity metric implemented by d-Matrix.
Perplexity (PPL) is one of the most common metrics for evaluating language models.
It is defined as the exponentiated average negative log-likelihood of a sequence, calculated with exponent base `e`.
Note that this metric is intended for Causual Language Models, the perplexity calculation is only correct if model uses Cross Entropy Loss.
For more information, see https://huggingface.co/docs/transformers/perplexity

## How to Use
At minimum, this metric requires the model and references as inputs.
```python
>>> import evaluate
>>> perplexity = evaluate.load("d-matrix/dmx_perplexity", module_type="metric")
>>> input_texts = ["lorem ipsum", "Happy Birthday!", "Bienvenue"]
>>> results = perplexity.compute(model='distilgpt2',references=input_texts)
>>> print(results)
{'loss': 4.993086338043213, 'perplexity': 147.390625}
```

### Inputs
- **model** (`Union`[`str`,`AutoModelForCausalLM`]): model used for calculating Perplexity
- **references** (`list` of `str`): input text, each separate text snippet is one list entry.
- **device** (`str`): device to run on, defaults to 'cuda' when available.
- **max_length** (`int`): maximum sequence length, defaults to 2048.

### Output Values
- **loss** (`float`): the loss of the model predictions compared to the reference
- **perplexity**(`float`): measures the uncertainty of a model predicting text. Model performance is better when perplexity is lower.

Output Example(s):
```python
{'loss': 4.993086338043213, 'perplexity': 147.390625}
```
This metric outputs a dictionary, containing the loss and perplexity score.

### Examples
```python
>>> import evaluate
>>> from datasets import load_dataset
>>> from transformers import AutoTokenizer, AutoModelForCausalLM
>>> perplexity = evaluate.load("d-matrix/dmx_perplexity", module_type="metric")
>>> input_texts = load_dataset("wikitext", "wikitext-2-raw-v1", split="test")["text"][:10]
>>> model = AutoModelForCausalLM.from_pretrained("distilgpt2")
>>> results = perplexity.compute(model=model,references=input_texts)
>>> print(list(results.keys()))
['loss', 'perplexity']
>>> print(results['loss']) 
3.9706921577453613
>>> print(results['perplexity']) 
53.021217346191406
```

## Citation(s)
https://huggingface.co/docs/transformers/perplexity