# SwiftFormer

## SwiftFormer

### Overview

The SwiftFormer model was proposed in [SwiftFormer: Efficient Additive Attention for Transformer-based Real-time Mobile Vision Applications](https://arxiv.org/abs/2303.15446) by Abdelrahman Shaker, Muhammad Maaz, Hanoona Rasheed, Salman Khan, Ming-Hsuan Yang, Fahad Shahbaz Khan.

The SwiftFormer paper introduces a novel efficient additive attention mechanism that effectively replaces the quadratic matrix multiplication operations in the self-attention computation with linear element-wise multiplications. A series of models called ‘SwiftFormer’ is built based on this, which achieves state-of-the-art performance in terms of both accuracy and mobile inference speed. Even their small variant achieves 78.5% top-1 ImageNet1K accuracy with only 0.8 ms latency on iPhone 14, which is more accurate and 2× faster compared to MobileViT-v2.

The abstract from the paper is the following:

*Self-attention has become a defacto choice for capturing global context in various vision applications. However, its quadratic computational complexity with respect to image resolution limits its use in real-time applications, especially for deployment on resource-constrained mobile devices. Although hybrid approaches have been proposed to combine the advantages of convolutions and self-attention for a better speed-accuracy trade-off, the expensive matrix multiplication operations in self-attention remain a bottleneck. In this work, we introduce a novel efficient additive attention mechanism that effectively replaces the quadratic matrix multiplication operations with linear element-wise multiplications. Our design shows that the key-value interaction can be replaced with a linear layer without sacrificing any accuracy. Unlike previous state-of-the-art methods, our efficient formulation of self-attention enables its usage at all stages of the network. Using our proposed efficient additive attention, we build a series of models called “SwiftFormer” which achieves state-of-the-art performance in terms of both accuracy and mobile inference speed. Our small variant achieves 78.5% top-1 ImageNet-1K accuracy with only 0.8 ms latency on iPhone 14, which is more accurate and 2x faster compared to MobileViT-v2.*

Tips:

* One can use the [ViTImageProcessor](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/vit#transformers.ViTImageProcessor) API to prepare images for the model.

This model was contributed by [shehan97](https://huggingface.co/shehan97). The original code can be found [here](https://github.com/Amshaker/SwiftFormer).

### SwiftFormerConfig

#### class transformers.SwiftFormerConfig

[\<source>](https://github.com/huggingface/transformers/blob/v4.34.1/src/transformers/models/swiftformer/configuration_swiftformer.py#L34)

( num\_channels = 3depths = \[3, 3, 6, 4]embed\_dims = \[48, 56, 112, 220]mlp\_ratio = 4downsamples = \[True, True, True, True]hidden\_act = 'gelu'down\_patch\_size = 3down\_stride = 2down\_pad = 1drop\_path\_rate = 0.0use\_layer\_scale = Truelayer\_scale\_init\_value = 1e-05batch\_norm\_eps = 1e-05\*\*kwargs )

Parameters

* **num\_channels** (`int`, *optional*, defaults to 3) — The number of input channels
* **depths** (`List[int]`, *optional*, defaults to `[3, 3, 6, 4]`) — Depth of each stage
* **embed\_dims** (`List[int]`, *optional*, defaults to `[48, 56, 112, 220]`) — The embedding dimension at each stage
* **mlp\_ratio** (`int`, *optional*, defaults to 4) — Ratio of size of the hidden dimensionality of an MLP to the dimensionality of its input.
* **downsamples** (`List[bool]`, *optional*, defaults to `[True, True, True, True]`) — Whether or not to downsample inputs between two stages.
* **hidden\_act** (`str`, *optional*, defaults to `"gelu"`) — The non-linear activation function (string). `"gelu"`, `"relu"`, `"selu"` and `"gelu_new"` are supported.
* **down\_patch\_size** (`int`, *optional*, defaults to 3) — The size of patches in downsampling layers.
* **down\_stride** (`int`, *optional*, defaults to 2) — The stride of convolution kernels in downsampling layers.
* **down\_pad** (`int`, *optional*, defaults to 1) — Padding in downsampling layers.
* **drop\_path\_rate** (`float`, *optional*, defaults to 0.) — Rate at which to increase dropout probability in DropPath.
* **use\_layer\_scale** (`bool`, *optional*, defaults to `True`) — Whether to scale outputs from token mixers.
* **layer\_scale\_init\_value** (`float`, *optional*, defaults to 1e-5) — Factor by which outputs from token mixers are scaled.
* **batch\_norm\_eps** (`float`, *optional*, defaults to 1e-5) — The epsilon used by the batch normalization layers.

This is the configuration class to store the configuration of a [SwiftFormerModel](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerModel). It is used to instantiate an SwiftFormer model according to the specified arguments, defining the model architecture. Instantiating a configuration with the defaults will yield a similar configuration to that of the SwiftFormer [MBZUAI/swiftformer-xs](https://huggingface.co/MBZUAI/swiftformer-xs) architecture.

Configuration objects inherit from [PretrainedConfig](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/configuration#transformers.PretrainedConfig) and can be used to control the model outputs. Read the documentation from [PretrainedConfig](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/configuration#transformers.PretrainedConfig) for more information.

Example:

Copied

```
>>> from transformers import SwiftFormerConfig, SwiftFormerModel

>>> # Initializing a SwiftFormer swiftformer-base-patch16-224 style configuration
>>> configuration = SwiftFormerConfig()

>>> # Initializing a model (with random weights) from the swiftformer-base-patch16-224 style configuration
>>> model = SwiftFormerModel(configuration)

>>> # Accessing the model configuration
>>> configuration = model.config
```

### SwiftFormerModel

#### class transformers.SwiftFormerModel

[\<source>](https://github.com/huggingface/transformers/blob/v4.34.1/src/transformers/models/swiftformer/modeling_swiftformer.py#L479)

( config: SwiftFormerConfig )

Parameters

* **config** ([SwiftFormerConfig](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerConfig)) — Model configuration class with all the parameters of the model. Initializing with a config file does not load the weights associated with the model, only the configuration. Check out the [from\_pretrained()](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/model#transformers.PreTrainedModel.from_pretrained) method to load the model weights.

The bare SwiftFormer Model transformer outputting raw hidden-states without any specific head on top. This model is a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) subclass. Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage and behavior.

**forward**

[\<source>](https://github.com/huggingface/transformers/blob/v4.34.1/src/transformers/models/swiftformer/modeling_swiftformer.py#L490)

( pixel\_values: typing.Optional\[torch.Tensor] = Noneoutput\_hidden\_states: typing.Optional\[bool] = Nonereturn\_dict: typing.Optional\[bool] = None ) → `transformers.modeling_outputs.BaseModelOutputWithNoAttention` or `tuple(torch.FloatTensor)`

Parameters

* **pixel\_values** (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`) — Pixel values. Pixel values can be obtained using [AutoImageProcessor](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/auto#transformers.AutoImageProcessor). See [ViTImageProcessor.**call**()](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/deit#transformers.DeiTFeatureExtractor.__call__) for details.
* **output\_hidden\_states** (`bool`, *optional*) — Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors for more detail.
* **return\_dict** (`bool`, *optional*) — Whether or not to return a [ModelOutput](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/output#transformers.utils.ModelOutput) instead of a plain tuple.

Returns

`transformers.modeling_outputs.BaseModelOutputWithNoAttention` or `tuple(torch.FloatTensor)`

A `transformers.modeling_outputs.BaseModelOutputWithNoAttention` or a tuple of `torch.FloatTensor` (if `return_dict=False` is passed or when `config.return_dict=False`) comprising various elements depending on the configuration ([SwiftFormerConfig](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerConfig)) and inputs.

* **last\_hidden\_state** (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`) — Sequence of hidden-states at the output of the last layer of the model.
* **hidden\_states** (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`) — Tuple of `torch.FloatTensor` (one for the output of the embeddings, if the model has an embedding layer, + one for the output of each layer) of shape `(batch_size, num_channels, height, width)`.

  Hidden-states of the model at the output of each layer plus the optional initial embedding outputs.

The [SwiftFormerModel](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerModel) forward method, overrides the `__call__` special method.

Although the recipe for forward pass needs to be defined within this function, one should call the `Module` instance afterwards instead of this since the former takes care of running the pre and post processing steps while the latter silently ignores them.

Example:

Copied

```
>>> from transformers import AutoImageProcessor, SwiftFormerModel
>>> import torch
>>> from datasets import load_dataset

>>> dataset = load_dataset("boincai/cats-image")
>>> image = dataset["test"]["image"][0]

>>> image_processor = AutoImageProcessor.from_pretrained("MBZUAI/swiftformer-xs")
>>> model = SwiftFormerModel.from_pretrained("MBZUAI/swiftformer-xs")

>>> inputs = image_processor(image, return_tensors="pt")

>>> with torch.no_grad():
...     outputs = model(**inputs)

>>> last_hidden_states = outputs.last_hidden_state
>>> list(last_hidden_states.shape)
[1, 220, 7, 7]
```

### SwiftFormerForImageClassification

#### class transformers.SwiftFormerForImageClassification

[\<source>](https://github.com/huggingface/transformers/blob/v4.34.1/src/transformers/models/swiftformer/modeling_swiftformer.py#L536)

( config: SwiftFormerConfig )

Parameters

* **config** ([SwiftFormerConfig](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerConfig)) — Model configuration class with all the parameters of the model. Initializing with a config file does not load the weights associated with the model, only the configuration. Check out the [from\_pretrained()](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/model#transformers.PreTrainedModel.from_pretrained) method to load the model weights.

SwiftFormer Model transformer with an image classification head on top (e.g. for ImageNet).

This model is a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) subclass. Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage and behavior.

**forward**

[\<source>](https://github.com/huggingface/transformers/blob/v4.34.1/src/transformers/models/swiftformer/modeling_swiftformer.py#L553)

( pixel\_values: typing.Optional\[torch.Tensor] = Nonelabels: typing.Optional\[torch.Tensor] = Noneoutput\_hidden\_states: typing.Optional\[bool] = Nonereturn\_dict: typing.Optional\[bool] = None ) → [transformers.modeling\_outputs.ImageClassifierOutputWithNoAttention](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/output#transformers.modeling_outputs.ImageClassifierOutputWithNoAttention) or `tuple(torch.FloatTensor)`

Parameters

* **pixel\_values** (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`) — Pixel values. Pixel values can be obtained using [AutoImageProcessor](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/auto#transformers.AutoImageProcessor). See [ViTImageProcessor.**call**()](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/deit#transformers.DeiTFeatureExtractor.__call__) for details.
* **output\_hidden\_states** (`bool`, *optional*) — Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors for more detail.
* **return\_dict** (`bool`, *optional*) — Whether or not to return a [ModelOutput](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/output#transformers.utils.ModelOutput) instead of a plain tuple.
* **labels** (`torch.LongTensor` of shape `(batch_size,)`, *optional*) — Labels for computing the image classification/regression loss. Indices should be in `[0, ..., config.num_labels - 1]`. If `config.num_labels == 1` a regression loss is computed (Mean-Square loss), If `config.num_labels > 1` a classification loss is computed (Cross-Entropy).

Returns

[transformers.modeling\_outputs.ImageClassifierOutputWithNoAttention](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/output#transformers.modeling_outputs.ImageClassifierOutputWithNoAttention) or `tuple(torch.FloatTensor)`

A [transformers.modeling\_outputs.ImageClassifierOutputWithNoAttention](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/output#transformers.modeling_outputs.ImageClassifierOutputWithNoAttention) or a tuple of `torch.FloatTensor` (if `return_dict=False` is passed or when `config.return_dict=False`) comprising various elements depending on the configuration ([SwiftFormerConfig](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerConfig)) and inputs.

* **loss** (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `labels` is provided) — Classification (or regression if config.num\_labels==1) loss.
* **logits** (`torch.FloatTensor` of shape `(batch_size, config.num_labels)`) — Classification (or regression if config.num\_labels==1) scores (before SoftMax).
* **hidden\_states** (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`) — Tuple of `torch.FloatTensor` (one for the output of the embeddings, if the model has an embedding layer, + one for the output of each stage) of shape `(batch_size, num_channels, height, width)`. Hidden-states (also called feature maps) of the model at the output of each stage.

The [SwiftFormerForImageClassification](https://huggingface.co/docs/transformers/v4.34.1/en/model_doc/swiftformer#transformers.SwiftFormerForImageClassification) forward method, overrides the `__call__` special method.

Although the recipe for forward pass needs to be defined within this function, one should call the `Module` instance afterwards instead of this since the former takes care of running the pre and post processing steps while the latter silently ignores them.

Example:

Copied

```
>>> from transformers import AutoImageProcessor, SwiftFormerForImageClassification
>>> import torch
>>> from datasets import load_dataset

>>> dataset = load_dataset("boincai/cats-image")
>>> image = dataset["test"]["image"][0]

>>> image_processor = AutoImageProcessor.from_pretrained("MBZUAI/swiftformer-xs")
>>> model = SwiftFormerForImageClassification.from_pretrained("MBZUAI/swiftformer-xs")

>>> inputs = image_processor(image, return_tensors="pt")

>>> with torch.no_grad():
...     logits = model(**inputs).logits

>>> # model predicts one of the 1000 ImageNet classes
>>> predicted_label = logits.argmax(-1).item()
>>> print(model.config.id2label[predicted_label])
tabby, tabby cat
```


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