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# Benchmarks

Let's take a look at how 🤗 Transformer models can be benchmarked, best practices, and already available benchmarks.

A notebook explaining in more detail how to benchmark 🤗 Transformer models can be found [here](https://github.com/huggingface/transformers/tree/master/notebooks/05-benchmark.ipynb).

## How to benchmark 🤗 Transformer models

The classes [`PyTorchBenchmark`] and [`TensorFlowBenchmark`] allow to flexibly benchmark 🤗 Transformer models. The benchmark classes allow us to measure the _peak memory usage_ and _required time_ for both _inference_ and _training_.

<Tip>

Hereby, _inference_ is defined by a single forward pass, and _training_ is defined by a single forward pass and
backward pass.

</Tip>

The benchmark classes [`PyTorchBenchmark`] and [`TensorFlowBenchmark`] expect an object of type [`PyTorchBenchmarkArguments`] and
[`TensorFlowBenchmarkArguments`], respectively, for instantiation. [`PyTorchBenchmarkArguments`] and [`TensorFlowBenchmarkArguments`] are data classes and contain all relevant configurations for their corresponding benchmark class. In the following example, it is shown how a BERT model of type _bert-base-cased_ can be benchmarked.

```py
>>> from transformers import PyTorchBenchmark, PyTorchBenchmarkArguments

>>> args = PyTorchBenchmarkArguments(models=["bert-base-uncased"], batch_sizes=[8], sequence_lengths=[8, 32, 128, 512])
>>> benchmark = PyTorchBenchmark(args)

===PT-TF-SPLIT===
>>> from transformers import TensorFlowBenchmark, TensorFlowBenchmarkArguments

>>> args = TensorFlowBenchmarkArguments(models=["bert-base-uncased"], batch_sizes=[8], sequence_lengths=[8, 32, 128, 512])
>>> benchmark = TensorFlowBenchmark(args)
```

Here, three arguments are given to the benchmark argument data classes, namely `models`, `batch_sizes`, and
`sequence_lengths`. The argument `models` is required and expects a `list` of model identifiers from the
[model hub](https://huggingface.co/models) The `list` arguments `batch_sizes` and `sequence_lengths` define
the size of the `input_ids` on which the model is benchmarked. There are many more parameters that can be configured
via the benchmark argument data classes. For more detail on these one can either directly consult the files
`src/transformers/benchmark/benchmark_args_utils.py`, `src/transformers/benchmark/benchmark_args.py` (for PyTorch)
and `src/transformers/benchmark/benchmark_args_tf.py` (for Tensorflow). Alternatively, running the following shell
commands from root will print out a descriptive list of all configurable parameters for PyTorch and Tensorflow
respectively.

```bash
python examples/pytorch/benchmarking/run_benchmark.py --help

===PT-TF-SPLIT===
python examples/tensorflow/benchmarking/run_benchmark_tf.py --help
```

An instantiated benchmark object can then simply be run by calling `benchmark.run()`.

```py
>>> results = benchmark.run()
>>> print(results)
====================       INFERENCE - SPEED - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length     Time in s                  
--------------------------------------------------------------------------------
bert-base-uncased          8               8             0.006     
bert-base-uncased          8               32            0.006     
bert-base-uncased          8              128            0.018     
bert-base-uncased          8              512            0.088     
--------------------------------------------------------------------------------

====================      INFERENCE - MEMORY - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length    Memory in MB 
--------------------------------------------------------------------------------
bert-base-uncased          8               8             1227
bert-base-uncased          8               32            1281
bert-base-uncased          8              128            1307
bert-base-uncased          8              512            1539
--------------------------------------------------------------------------------

====================        ENVIRONMENT INFORMATION         ====================

- transformers_version: 2.11.0
- framework: PyTorch
- use_torchscript: False
- framework_version: 1.4.0
- python_version: 3.6.10
- system: Linux
- cpu: x86_64
- architecture: 64bit
- date: 2020-06-29
- time: 08:58:43.371351
- fp16: False
- use_multiprocessing: True
- only_pretrain_model: False
- cpu_ram_mb: 32088
- use_gpu: True
- num_gpus: 1
- gpu: TITAN RTX
- gpu_ram_mb: 24217
- gpu_power_watts: 280.0
- gpu_performance_state: 2
- use_tpu: False

===PT-TF-SPLIT===
>>> results = benchmark.run()
>>> print(results)
====================       INFERENCE - SPEED - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length     Time in s                  
--------------------------------------------------------------------------------
bert-base-uncased          8               8             0.005
bert-base-uncased          8               32            0.008
bert-base-uncased          8              128            0.022
bert-base-uncased          8              512            0.105
--------------------------------------------------------------------------------

====================      INFERENCE - MEMORY - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length    Memory in MB 
--------------------------------------------------------------------------------
bert-base-uncased          8               8             1330
bert-base-uncased          8               32            1330
bert-base-uncased          8              128            1330
bert-base-uncased          8              512            1770
--------------------------------------------------------------------------------

====================        ENVIRONMENT INFORMATION         ====================

- transformers_version: 2.11.0
- framework: Tensorflow
- use_xla: False
- framework_version: 2.2.0
- python_version: 3.6.10
- system: Linux
- cpu: x86_64
- architecture: 64bit
- date: 2020-06-29
- time: 09:26:35.617317
- fp16: False
- use_multiprocessing: True
- only_pretrain_model: False
- cpu_ram_mb: 32088
- use_gpu: True
- num_gpus: 1
- gpu: TITAN RTX
- gpu_ram_mb: 24217
- gpu_power_watts: 280.0
- gpu_performance_state: 2
- use_tpu: False
```

By default, the _time_ and the _required memory_ for _inference_ are benchmarked. In the example output above the first
two sections show the result corresponding to _inference time_ and _inference memory_. In addition, all relevant
information about the computing environment, _e.g._ the GPU type, the system, the library versions, etc... are printed
out in the third section under _ENVIRONMENT INFORMATION_. This information can optionally be saved in a _.csv_ file
when adding the argument `save_to_csv=True` to [`PyTorchBenchmarkArguments`] and
[`TensorFlowBenchmarkArguments`] respectively. In this case, every section is saved in a separate
_.csv_ file. The path to each _.csv_ file can optionally be defined via the argument data classes.

Instead of benchmarking pre-trained models via their model identifier, _e.g._ `bert-base-uncased`, the user can
alternatively benchmark an arbitrary configuration of any available model class. In this case, a `list` of
configurations must be inserted with the benchmark args as follows.

```py
>>> from transformers import PyTorchBenchmark, PyTorchBenchmarkArguments, BertConfig

>>> args = PyTorchBenchmarkArguments(models=["bert-base", "bert-384-hid", "bert-6-lay"], batch_sizes=[8], sequence_lengths=[8, 32, 128, 512])
>>> config_base = BertConfig()
>>> config_384_hid = BertConfig(hidden_size=384)
>>> config_6_lay = BertConfig(num_hidden_layers=6)

>>> benchmark = PyTorchBenchmark(args, configs=[config_base, config_384_hid, config_6_lay])
>>> benchmark.run()
====================       INFERENCE - SPEED - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length       Time in s                  
--------------------------------------------------------------------------------
bert-base                  8              128            0.006
bert-base                  8              512            0.006
bert-base                  8              128            0.018     
bert-base                  8              512            0.088     
bert-384-hid              8               8             0.006     
bert-384-hid              8               32            0.006     
bert-384-hid              8              128            0.011     
bert-384-hid              8              512            0.054     
bert-6-lay                 8               8             0.003     
bert-6-lay                 8               32            0.004     
bert-6-lay                 8              128            0.009     
bert-6-lay                 8              512            0.044
--------------------------------------------------------------------------------

====================      INFERENCE - MEMORY - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length      Memory in MB 
--------------------------------------------------------------------------------
bert-base                  8               8             1277
bert-base                  8               32            1281
bert-base                  8              128            1307     
bert-base                  8              512            1539     
bert-384-hid              8               8             1005     
bert-384-hid              8               32            1027     
bert-384-hid              8              128            1035     
bert-384-hid              8              512            1255     
bert-6-lay                 8               8             1097     
bert-6-lay                 8               32            1101     
bert-6-lay                 8              128            1127     
bert-6-lay                 8              512            1359
--------------------------------------------------------------------------------

====================        ENVIRONMENT INFORMATION         ====================

- transformers_version: 2.11.0
- framework: PyTorch
- use_torchscript: False
- framework_version: 1.4.0
- python_version: 3.6.10
- system: Linux
- cpu: x86_64
- architecture: 64bit
- date: 2020-06-29
- time: 09:35:25.143267
- fp16: False
- use_multiprocessing: True
- only_pretrain_model: False
- cpu_ram_mb: 32088
- use_gpu: True
- num_gpus: 1
- gpu: TITAN RTX
- gpu_ram_mb: 24217
- gpu_power_watts: 280.0
- gpu_performance_state: 2
- use_tpu: False

===PT-TF-SPLIT===
>>> from transformers import TensorFlowBenchmark, TensorFlowBenchmarkArguments, BertConfig

>>> args = TensorFlowBenchmarkArguments(models=["bert-base", "bert-384-hid", "bert-6-lay"], batch_sizes=[8], sequence_lengths=[8, 32, 128, 512])
>>> config_base = BertConfig()
>>> config_384_hid = BertConfig(hidden_size=384)
>>> config_6_lay = BertConfig(num_hidden_layers=6)

>>> benchmark = TensorFlowBenchmark(args, configs=[config_base, config_384_hid, config_6_lay])
>>> benchmark.run()
====================       INFERENCE - SPEED - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length       Time in s                  
--------------------------------------------------------------------------------
bert-base                  8               8             0.005
bert-base                  8               32            0.008
bert-base                  8              128            0.022
bert-base                  8              512            0.106
bert-384-hid              8               8             0.005
bert-384-hid              8               32            0.007
bert-384-hid              8              128            0.018
bert-384-hid              8              512            0.064
bert-6-lay                 8               8             0.002
bert-6-lay                 8               32            0.003
bert-6-lay                 8              128            0.0011
bert-6-lay                 8              512            0.074
--------------------------------------------------------------------------------

====================      INFERENCE - MEMORY - RESULT       ====================
--------------------------------------------------------------------------------
Model Name             Batch Size     Seq Length      Memory in MB 
--------------------------------------------------------------------------------
bert-base                  8               8             1330
bert-base                  8               32            1330
bert-base                  8              128            1330
bert-base                  8              512            1770
bert-384-hid              8               8             1330
bert-384-hid              8               32            1330
bert-384-hid              8              128            1330
bert-384-hid              8              512            1540
bert-6-lay                 8               8             1330
bert-6-lay                 8               32            1330
bert-6-lay                 8              128            1330
bert-6-lay                 8              512            1540
--------------------------------------------------------------------------------

====================        ENVIRONMENT INFORMATION         ====================

- transformers_version: 2.11.0
- framework: Tensorflow
- use_xla: False
- framework_version: 2.2.0
- python_version: 3.6.10
- system: Linux
- cpu: x86_64
- architecture: 64bit
- date: 2020-06-29
- time: 09:38:15.487125
- fp16: False
- use_multiprocessing: True
- only_pretrain_model: False
- cpu_ram_mb: 32088
- use_gpu: True
- num_gpus: 1
- gpu: TITAN RTX
- gpu_ram_mb: 24217
- gpu_power_watts: 280.0
- gpu_performance_state: 2
- use_tpu: False
```

Again, _inference time_ and _required memory_ for _inference_ are measured, but this time for customized configurations
of the `BertModel` class. This feature can especially be helpful when deciding for which configuration the model
should be trained.


## Benchmark best practices

This section lists a couple of best practices one should be aware of when benchmarking a model.

- Currently, only single device benchmarking is supported. When benchmarking on GPU, it is recommended that the user
  specifies on which device the code should be run by setting the `CUDA_VISIBLE_DEVICES` environment variable in the
  shell, _e.g._ `export CUDA_VISIBLE_DEVICES=0` before running the code.
- The option `no_multi_processing` should only be set to `True` for testing and debugging. To ensure accurate
  memory measurement it is recommended to run each memory benchmark in a separate process by making sure
  `no_multi_processing` is set to `True`.
- One should always state the environment information when sharing the results of a model benchmark. Results can vary
  heavily between different GPU devices, library versions, etc., so that benchmark results on their own are not very
  useful for the community.


## Sharing your benchmark

Previously all available core models (10 at the time) have been benchmarked for _inference time_, across many different
settings: using PyTorch, with and without TorchScript, using TensorFlow, with and without XLA. All of those tests were
done across CPUs (except for TensorFlow XLA) and GPUs.

The approach is detailed in the [following blogpost](https://medium.com/huggingface/benchmarking-transformers-pytorch-and-tensorflow-e2917fb891c2) and the results are
available [here](https://docs.google.com/spreadsheets/d/1sryqufw2D0XlUH4sq3e9Wnxu5EAQkaohzrJbd5HdQ_w/edit?usp=sharing).

With the new _benchmark_ tools, it is easier than ever to share your benchmark results with the community

- [PyTorch Benchmarking Results](https://github.com/huggingface/transformers/tree/master/examples/pytorch/benchmarking/README.md).
- [TensorFlow Benchmarking Results](https://github.com/huggingface/transformers/tree/master/examples/tensorflow/benchmarking/README.md).
