Flax VisionTransformer (#11951)

* adding vit for flax

* added test for Flax-vit and some bug-fixes

* overrided methods where variable changes were necessary for flax_vit test

* added FlaxViTForImageClassification for test

* Update src/transformers/models/vit/modeling_flax_vit.py

Co-authored-by: Suraj Patil <surajp815@gmail.com>

* made changes suggested in PR

* Adding jax-vit models for autoimport

* swapping num_channels and height,width dimension

* fixing the docstring for torch-like inputs for VIT

* add model to main init

* add docs

* doc, fix-copies

* docstrings

* small test fixes

* fix docs

* fix docstr

* Apply suggestions from code review

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* style

Co-authored-by: jayendra <jayendra@infocusp.in>
Co-authored-by: Suraj Patil <surajp815@gmail.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

docs/source/index.rst

@@ -395,7 +395,7 @@ Flax), PyTorch, and/or TensorFlow.
 +-----------------------------+----------------+----------------+-----------------+--------------------+--------------+
 |       Transformer-XL        |       ✅       |       ❌       |       ✅        |         ✅         |      ❌      |
 +-----------------------------+----------------+----------------+-----------------+--------------------+--------------+
-|             ViT             |       ❌       |       ❌       |       ✅        |         ❌         |      ❌      |
+|             ViT             |       ❌       |       ❌       |       ✅        |         ❌         |      ✅      |
 +-----------------------------+----------------+----------------+-----------------+--------------------+--------------+
 |         VisualBert          |       ❌       |       ❌       |       ✅        |         ❌         |      ❌      |
 +-----------------------------+----------------+----------------+-----------------+--------------------+--------------+

docs/source/model_doc/vit.rst

@@ -101,3 +101,18 @@ ViTForImageClassification
 
 .. autoclass:: transformers.ViTForImageClassification
     :members: forward
+
+
+FlaxVitModel
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.FlaxViTModel
+    :members: __call__
+
+
+FlaxViTForImageClassification
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.FlaxViTForImageClassification
+    :members: __call__
+

src/transformers/__init__.py

@@ -1553,6 +1553,7 @@ if is_flax_available():
             "FlaxRobertaPreTrainedModel",
         ]
     )
+    _import_structure["models.vit"].extend(["FlaxViTForImageClassification", "FlaxViTModel"])
 else:
     from .utils import dummy_flax_objects
 
@@ -2839,6 +2840,7 @@ if TYPE_CHECKING:
             FlaxRobertaModel,
             FlaxRobertaPreTrainedModel,
         )
+        from .models.vit import FlaxViTForImageClassification, FlaxViTModel
     else:
         # Import the same objects as dummies to get them in the namespace.
         # They will raise an import error if the user tries to instantiate / use them.

src/transformers/models/auto/__init__.py

@@ -97,6 +97,7 @@ if is_flax_available():
         "FLAX_MODEL_MAPPING",
         "FlaxAutoModel",
         "FlaxAutoModelForCausalLM",
+        "FlaxAutoModelForImageClassification",
         "FlaxAutoModelForMaskedLM",
         "FlaxAutoModelForMultipleChoice",
         "FlaxAutoModelForNextSentencePrediction",
@@ -182,6 +183,7 @@ if TYPE_CHECKING:
             FLAX_MODEL_MAPPING,
             FlaxAutoModel,
             FlaxAutoModelForCausalLM,
+            FlaxAutoModelForImageClassification,
             FlaxAutoModelForMaskedLM,
             FlaxAutoModelForMultipleChoice,
             FlaxAutoModelForNextSentencePrediction,

src/transformers/models/auto/modeling_flax_auto.py

@@ -47,8 +47,9 @@ from ..roberta.modeling_flax_roberta import (
     FlaxRobertaForTokenClassification,
     FlaxRobertaModel,
 )
+from ..vit.modeling_flax_vit import FlaxViTForImageClassification, FlaxViTModel
 from .auto_factory import auto_class_factory
-from .configuration_auto import BertConfig, CLIPConfig, ElectraConfig, GPT2Config, RobertaConfig
+from .configuration_auto import BertConfig, CLIPConfig, ElectraConfig, GPT2Config, RobertaConfig, ViTConfig
 
 
 logger = logging.get_logger(__name__)
@@ -62,6 +63,7 @@ FLAX_MODEL_MAPPING = OrderedDict(
         (GPT2Config, FlaxGPT2Model),
         (ElectraConfig, FlaxElectraModel),
         (CLIPConfig, FlaxCLIPModel),
+        (ViTConfig, FlaxViTModel),
     ]
 )
 
@@ -83,6 +85,13 @@ FLAX_MODEL_FOR_MASKED_LM_MAPPING = OrderedDict(
     ]
 )
 
+FLAX_MODEL_FOR_IMAGECLASSIFICATION_MAPPING = OrderedDict(
+    [
+        # Model for Image-classsification
+        (ViTConfig, FlaxViTForImageClassification),
+    ]
+)
+
 FLAX_MODEL_FOR_CAUSAL_LM_MAPPING = OrderedDict(
     [
         # Model for Causal LM mapping
@@ -134,6 +143,12 @@ FLAX_MODEL_FOR_NEXT_SENTENCE_PREDICTION_MAPPING = OrderedDict(
 
 FlaxAutoModel = auto_class_factory("FlaxAutoModel", FLAX_MODEL_MAPPING)
 
+FlaxAutoModelForImageClassification = auto_class_factory(
+    "FlaxAutoModelForImageClassification",
+    FLAX_MODEL_FOR_IMAGECLASSIFICATION_MAPPING,
+    head_doc="image classification modeling",
+)
+
 FlaxAutoModelForCausalLM = auto_class_factory(
     "FlaxAutoModelForCausalLM", FLAX_MODEL_FOR_CAUSAL_LM_MAPPING, head_doc="causal language modeling"
 )

src/transformers/models/vit/__init__.py

@@ -17,7 +17,7 @@
 # limitations under the License.
 from typing import TYPE_CHECKING
 
-from ...file_utils import _BaseLazyModule, is_torch_available, is_vision_available
+from ...file_utils import _BaseLazyModule, is_flax_available, is_torch_available, is_vision_available
 
 
 _import_structure = {
@@ -36,6 +36,9 @@ if is_torch_available():
     ]
 
 
+if is_flax_available():
+    _import_structure["modeling_flax_vit"] = ["FlaxViTForImageClassification", "FlaxViTModel"]
+
 if TYPE_CHECKING:
     from .configuration_vit import VIT_PRETRAINED_CONFIG_ARCHIVE_MAP, ViTConfig
 
@@ -50,6 +53,9 @@ if TYPE_CHECKING:
             ViTPreTrainedModel,
         )
 
+    if is_flax_available():
+        from .modeling_flax_vit import FlaxViTForImageClassification, FlaxViTModel
+
 
 else:
     import importlib

src/transformers/models/vit/modeling_flax_vit.py

@@ -0,0 +1,606 @@
+# coding=utf-8
+# Copyright 2021 The Google Flax Team Authors and The HuggingFace Inc. team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import Optional, Tuple
+
+import flax.linen as nn
+import jax
+import jax.numpy as jnp
+from flax.core.frozen_dict import FrozenDict
+from flax.linen.attention import dot_product_attention_weights
+
+from ...file_utils import add_start_docstrings, add_start_docstrings_to_model_forward
+from ...modeling_flax_outputs import FlaxBaseModelOutput, FlaxBaseModelOutputWithPooling, FlaxSequenceClassifierOutput
+from ...modeling_flax_utils import (
+    ACT2FN,
+    FlaxPreTrainedModel,
+    append_replace_return_docstrings,
+    overwrite_call_docstring,
+)
+from .configuration_vit import ViTConfig
+
+
+VIT_START_DOCSTRING = r"""
+
+    This model inherits from :class:`~transformers.FlaxPreTrainedModel`. Check the superclass documentation for the
+    generic methods the library implements for all its model (such as downloading, saving and converting weights from
+    PyTorch models)
+
+    This model is also a Flax Linen `flax.linen.Module
+    <https://flax.readthedocs.io/en/latest/flax.linen.html#module>`__ subclass. Use it as a regular Flax linen Module
+    and refer to the Flax documentation for all matter related to general usage and behavior.
+
+    Finally, this model supports inherent JAX features such as:
+
+    - `Just-In-Time (JIT) compilation <https://jax.readthedocs.io/en/latest/jax.html#just-in-time-compilation-jit>`__
+    - `Automatic Differentiation <https://jax.readthedocs.io/en/latest/jax.html#automatic-differentiation>`__
+    - `Vectorization <https://jax.readthedocs.io/en/latest/jax.html#vectorization-vmap>`__
+    - `Parallelization <https://jax.readthedocs.io/en/latest/jax.html#parallelization-pmap>`__
+
+    Parameters:
+        config (:class:`~transformers.ViTConfig`): 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 :meth:`~transformers.FlaxPreTrainedModel.from_pretrained` method to load the
+            model weights.
+"""
+
+VIT_INPUTS_DOCSTRING = r"""
+    Args:
+        pixel_values (:obj:`numpy.ndarray` of shape :obj:`(batch_size, num_channels, height, width)`):
+            Pixel values. Pixel values can be obtained using :class:`~transformers.ViTFeatureExtractor`. See
+            :meth:`transformers.ViTFeatureExtractor.__call__` for details.
+
+        output_attentions (:obj:`bool`, `optional`):
+            Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
+            tensors for more detail.
+        output_hidden_states (:obj:`bool`, `optional`):
+            Whether or not to return the hidden states of all layers. See ``hidden_states`` under returned tensors for
+            more detail.
+        return_dict (:obj:`bool`, `optional`):
+            Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.
+"""
+
+
+class FlaxPatchEmbeddings(nn.Module):
+
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        image_size = self.config.image_size
+        patch_size = self.config.patch_size
+        num_patches = (image_size // patch_size) * (image_size // patch_size)
+        self.num_patches = num_patches
+        self.projection = nn.Conv(
+            self.config.hidden_size,
+            kernel_size=(patch_size, patch_size),
+            strides=(patch_size, patch_size),
+            padding="VALID",
+            dtype=self.dtype,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+        )
+
+    def __call__(self, pixel_values):
+        x = self.projection(pixel_values)
+        batch_size, _, _, channels = x.shape
+        return jnp.reshape(x, (batch_size, -1, channels))
+
+
+class FlaxViTEmbeddings(nn.Module):
+    """Construct the CLS token, position and patch embeddings."""
+
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.cls_token = self.param("cls_token", nn.initializers.zeros, (1, 1, self.config.hidden_size))
+        self.patch_embeddings = FlaxPatchEmbeddings(self.config, dtype=self.dtype)
+        num_patches = self.patch_embeddings.num_patches
+        self.position_embeddings = self.param(
+            "position_embeddings", nn.initializers.zeros, (1, num_patches + 1, self.config.hidden_size)
+        )
+        self.dropout = nn.Dropout(rate=self.config.hidden_dropout_prob)
+
+    def __call__(self, pixel_values, deterministic=True):
+        batch_size = pixel_values.shape[0]
+
+        embeddings = self.patch_embeddings(pixel_values)
+
+        cls_tokens = jnp.broadcast_to(self.cls_token, (batch_size, 1, self.config.hidden_size))
+        embeddings = jnp.concatenate((cls_tokens, embeddings), axis=1)
+        embeddings = embeddings + self.position_embeddings
+        embeddings = self.dropout(embeddings, deterministic=deterministic)
+        return embeddings
+
+
+class FlaxViTSelfAttention(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        if self.config.hidden_size % self.config.num_attention_heads != 0:
+            raise ValueError(
+                "`config.hidden_size`: {self.config.hidden_size} has to be a multiple of `config.num_attention_heads`: {self.config.num_attention_heads}"
+            )
+
+        self.query = nn.Dense(
+            self.config.hidden_size,
+            dtype=self.dtype,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+        )
+        self.key = nn.Dense(
+            self.config.hidden_size,
+            dtype=self.dtype,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+        )
+        self.value = nn.Dense(
+            self.config.hidden_size,
+            dtype=self.dtype,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+        )
+
+    def __call__(self, hidden_states, deterministic: bool = True, output_attentions: bool = False):
+        head_dim = self.config.hidden_size // self.config.num_attention_heads
+
+        query_states = self.query(hidden_states).reshape(
+            hidden_states.shape[:2] + (self.config.num_attention_heads, head_dim)
+        )
+        value_states = self.value(hidden_states).reshape(
+            hidden_states.shape[:2] + (self.config.num_attention_heads, head_dim)
+        )
+        key_states = self.key(hidden_states).reshape(
+            hidden_states.shape[:2] + (self.config.num_attention_heads, head_dim)
+        )
+
+        dropout_rng = None
+        if not deterministic and self.config.attention_probs_dropout_prob > 0.0:
+            dropout_rng = self.make_rng("dropout")
+
+        attn_weights = dot_product_attention_weights(
+            query_states,
+            key_states,
+            dropout_rng=dropout_rng,
+            dropout_rate=self.config.attention_probs_dropout_prob,
+            broadcast_dropout=True,
+            deterministic=deterministic,
+            dtype=self.dtype,
+            precision=None,
+        )
+
+        attn_output = jnp.einsum("...hqk,...khd->...qhd", attn_weights, value_states)
+        attn_output = attn_output.reshape(attn_output.shape[:2] + (-1,))
+
+        outputs = (attn_output, attn_weights) if output_attentions else (attn_output,)
+        return outputs
+
+
+class FlaxViTSelfOutput(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.dense = nn.Dense(
+            self.config.hidden_size,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+            dtype=self.dtype,
+        )
+        self.dropout = nn.Dropout(rate=self.config.hidden_dropout_prob)
+
+    def __call__(self, hidden_states, input_tensor, deterministic: bool = True):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.dropout(hidden_states, deterministic=deterministic)
+        return hidden_states
+
+
+class FlaxViTAttention(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32
+
+    def setup(self):
+        self.attention = FlaxViTSelfAttention(self.config, dtype=self.dtype)
+        self.output = FlaxViTSelfOutput(self.config, dtype=self.dtype)
+
+    def __call__(self, hidden_states, deterministic=True, output_attentions: bool = False):
+        attn_outputs = self.attention(hidden_states, deterministic=deterministic, output_attentions=output_attentions)
+        attn_output = attn_outputs[0]
+        hidden_states = self.output(attn_output, hidden_states, deterministic=deterministic)
+
+        outputs = (hidden_states,)
+
+        if output_attentions:
+            outputs += (attn_outputs[1],)
+
+        return outputs
+
+
+class FlaxViTIntermediate(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.dense = nn.Dense(
+            self.config.intermediate_size,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+            dtype=self.dtype,
+        )
+        self.activation = ACT2FN[self.config.hidden_act]
+
+    def __call__(self, hidden_states):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.activation(hidden_states)
+        return hidden_states
+
+
+class FlaxViTOutput(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.dense = nn.Dense(
+            self.config.hidden_size,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+            dtype=self.dtype,
+        )
+        self.dropout = nn.Dropout(rate=self.config.hidden_dropout_prob)
+
+    def __call__(self, hidden_states, attention_output, deterministic: bool = True):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.dropout(hidden_states, deterministic=deterministic)
+        hidden_states = hidden_states + attention_output
+        return hidden_states
+
+
+class FlaxViTLayer(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.attention = FlaxViTAttention(self.config, dtype=self.dtype)
+        self.intermediate = FlaxViTIntermediate(self.config, dtype=self.dtype)
+        self.output = FlaxViTOutput(self.config, dtype=self.dtype)
+        self.layernorm_before = nn.LayerNorm(epsilon=self.config.layer_norm_eps, dtype=self.dtype)
+        self.layernorm_after = nn.LayerNorm(epsilon=self.config.layer_norm_eps, dtype=self.dtype)
+
+    def __call__(self, hidden_states, deterministic: bool = True, output_attentions: bool = False):
+        attention_outputs = self.attention(
+            self.layernorm_before(hidden_states),  # in ViT, layernorm is applied before self-attention
+            deterministic=deterministic,
+            output_attentions=output_attentions,
+        )
+
+        attention_output = attention_outputs[0]
+
+        # first residual connection
+        attention_output = attention_output + hidden_states
+
+        # in ViT, layernorm is also applied after self-attention
+        layer_output = self.layernorm_after(attention_output)
+
+        hidden_states = self.intermediate(layer_output)
+        hidden_states = self.output(hidden_states, attention_output, deterministic=deterministic)
+
+        outputs = (hidden_states,)
+
+        if output_attentions:
+            outputs += (attention_outputs[1],)
+        return outputs
+
+
+class FlaxViTLayerCollection(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.layers = [
+            FlaxViTLayer(self.config, name=str(i), dtype=self.dtype) for i in range(self.config.num_hidden_layers)
+        ]
+
+    def __call__(
+        self,
+        hidden_states,
+        deterministic: bool = True,
+        output_attentions: bool = False,
+        output_hidden_states: bool = False,
+        return_dict: bool = True,
+    ):
+
+        all_attentions = () if output_attentions else None
+        all_hidden_states = () if output_hidden_states else None
+
+        for i, layer in enumerate(self.layers):
+            if output_hidden_states:
+                all_hidden_states += (hidden_states,)
+
+            layer_outputs = layer(hidden_states, deterministic=deterministic, output_attentions=output_attentions)
+
+            hidden_states = layer_outputs[0]
+
+            if output_attentions:
+                all_attentions += (layer_outputs[1],)
+
+        if output_hidden_states:
+            all_hidden_states += (hidden_states,)
+
+        outputs = (hidden_states,)
+        if not return_dict:
+            return tuple(v for v in outputs if v is not None)
+
+        return FlaxBaseModelOutput(
+            last_hidden_state=hidden_states, hidden_states=all_hidden_states, attentions=all_attentions
+        )
+
+
+class FlaxViTEncoder(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.layer = FlaxViTLayerCollection(self.config, dtype=self.dtype)
+
+    def __call__(
+        self,
+        hidden_states,
+        deterministic: bool = True,
+        output_attentions: bool = False,
+        output_hidden_states: bool = False,
+        return_dict: bool = True,
+    ):
+        return self.layer(
+            hidden_states,
+            deterministic=deterministic,
+            output_attentions=output_attentions,
+            output_hidden_states=output_hidden_states,
+            return_dict=return_dict,
+        )
+
+
+class FlaxViTPooler(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+
+    def setup(self):
+        self.dense = nn.Dense(
+            self.config.hidden_size,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+            dtype=self.dtype,
+        )
+
+    def __call__(self, hidden_states):
+        cls_hidden_state = hidden_states[:, 0]
+        cls_hidden_state = self.dense(cls_hidden_state)
+        return nn.tanh(cls_hidden_state)
+
+
+class FlaxViTPreTrainedModel(FlaxPreTrainedModel):
+    """
+    An abstract class to handle weights initialization and a simple interface for downloading and loading pretrained
+    models.
+    """
+
+    config_class = ViTConfig
+    base_model_prefix = "vit"
+    module_class: nn.Module = None
+
+    def __init__(self, config: ViTConfig, input_shape=None, seed: int = 0, dtype: jnp.dtype = jnp.float32, **kwargs):
+        module = self.module_class(config=config, dtype=dtype, **kwargs)
+        if input_shape is None:
+            input_shape = (1, config.image_size, config.image_size, 3)
+        super().__init__(config, module, input_shape=input_shape, seed=seed, dtype=dtype)
+
+    def init_weights(self, rng: jax.random.PRNGKey, input_shape: Tuple) -> FrozenDict:
+        # init input tensors
+        pixel_values = jnp.zeros(input_shape, dtype=self.dtype)
+
+        params_rng, dropout_rng = jax.random.split(rng)
+        rngs = {"params": params_rng, "dropout": dropout_rng}
+
+        return self.module.init(rngs, pixel_values, return_dict=False)["params"]
+
+    @add_start_docstrings_to_model_forward(VIT_INPUTS_DOCSTRING.format("batch_size, sequence_length"))
+    def __call__(
+        self,
+        pixel_values,
+        params: dict = None,
+        dropout_rng: jax.random.PRNGKey = None,
+        train: bool = False,
+        output_attentions: Optional[bool] = None,
+        output_hidden_states: Optional[bool] = None,
+        return_dict: Optional[bool] = None,
+    ):
+        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
+        output_hidden_states = (
+            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
+        )
+        return_dict = return_dict if return_dict is not None else self.config.return_dict
+
+        pixel_values = jnp.transpose(pixel_values, (0, 2, 3, 1))
+        # Handle any PRNG if needed
+        rngs = {}
+        if dropout_rng is not None:
+            rngs["dropout"] = dropout_rng
+
+        return self.module.apply(
+            {"params": params or self.params},
+            jnp.array(pixel_values, dtype=jnp.float32),
+            not train,
+            output_attentions,
+            output_hidden_states,
+            return_dict,
+            rngs=rngs,
+        )
+
+
+class FlaxViTModule(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32  # the dtype of the computation
+    add_pooling_layer: bool = True
+
+    def setup(self):
+        self.embeddings = FlaxViTEmbeddings(self.config, dtype=self.dtype)
+        self.encoder = FlaxViTEncoder(self.config, dtype=self.dtype)
+        self.layernorm = nn.LayerNorm(epsilon=self.config.layer_norm_eps, dtype=self.dtype)
+        self.pooler = FlaxViTPooler(self.config, dtype=self.dtype) if self.add_pooling_layer else None
+
+    def __call__(
+        self,
+        pixel_values,
+        deterministic: bool = True,
+        output_attentions: bool = False,
+        output_hidden_states: bool = False,
+        return_dict: bool = True,
+    ):
+
+        hidden_states = self.embeddings(pixel_values, deterministic=deterministic)
+
+        outputs = self.encoder(
+            hidden_states,
+            deterministic=deterministic,
+            output_attentions=output_attentions,
+            output_hidden_states=output_hidden_states,
+            return_dict=return_dict,
+        )
+        hidden_states = outputs[0]
+        hidden_states = self.layernorm(hidden_states)
+        pooled = self.pooler(hidden_states) if self.add_pooling_layer else None
+
+        if not return_dict:
+            # if pooled is None, don't return it
+            if pooled is None:
+                return (hidden_states,) + outputs[1:]
+            return (hidden_states, pooled) + outputs[1:]
+
+        return FlaxBaseModelOutputWithPooling(
+            last_hidden_state=hidden_states,
+            pooler_output=pooled,
+            hidden_states=outputs.hidden_states,
+            attentions=outputs.attentions,
+        )
+
+
+@add_start_docstrings(
+    "The bare ViT Model transformer outputting raw hidden-states without any specific head on top.",
+    VIT_START_DOCSTRING,
+)
+class FlaxViTModel(FlaxViTPreTrainedModel):
+    module_class = FlaxViTModule
+
+
+FLAX_VISION_MODEL_DOCSTRING = """
+    Returns:
+
+    Examples::
+
+        >>> from transformers import ViTFeatureExtractor, FlaxViTModel
+        >>> from PIL import Image
+        >>> import requests
+
+        >>> url = 'http://images.cocodataset.org/val2017/000000039769.jpg'
+        >>> image = Image.open(requests.get(url, stream=True).raw)
+
+        >>> feature_extractor = ViTFeatureExtractor.from_pretrained('google/vit-base-patch16-224-in21k')
+        >>> model = FlaxViTModel.from_pretrained('google/vit-base-patch16-224-in21k')
+
+        >>> inputs = feature_extractor(images=image, return_tensors="jax")
+        >>> outputs = model(**inputs)
+        >>> last_hidden_states = outputs.last_hidden_state
+"""
+
+overwrite_call_docstring(FlaxViTModel, FLAX_VISION_MODEL_DOCSTRING)
+append_replace_return_docstrings(FlaxViTModel, output_type=FlaxBaseModelOutputWithPooling, config_class=ViTConfig)
+
+
+class FlaxViTForImageClassificationModule(nn.Module):
+    config: ViTConfig
+    dtype: jnp.dtype = jnp.float32
+
+    def setup(self):
+        self.vit = FlaxViTModule(config=self.config, dtype=self.dtype, add_pooling_layer=False)
+        self.classifier = nn.Dense(
+            self.config.num_labels,
+            dtype=self.dtype,
+            kernel_init=jax.nn.initializers.normal(self.config.initializer_range, self.dtype),
+        )
+
+    def __call__(
+        self,
+        pixel_values=None,
+        deterministic: bool = True,
+        output_attentions=None,
+        output_hidden_states=None,
+        return_dict=None,
+    ):
+        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
+
+        outputs = self.vit(
+            pixel_values,
+            deterministic=deterministic,
+            output_attentions=output_attentions,
+            output_hidden_states=output_hidden_states,
+            return_dict=return_dict,
+        )
+
+        hidden_states = outputs[0]
+        logits = self.classifier(hidden_states[:, 0, :])
+
+        if not return_dict:
+            output = (logits,) + outputs[2:]
+            return output
+
+        return FlaxSequenceClassifierOutput(
+            logits=logits,
+            hidden_states=outputs.hidden_states,
+            attentions=outputs.attentions,
+        )
+
+
+@add_start_docstrings(
+    """
+    ViT Model transformer with an image classification head on top (a linear layer on top of the final hidden state of
+    the [CLS] token) e.g. for ImageNet.
+    """,
+    VIT_START_DOCSTRING,
+)
+class FlaxViTForImageClassification(FlaxViTPreTrainedModel):
+    module_class = FlaxViTForImageClassificationModule
+
+
+FLAX_VISION_CLASSIF_DOCSTRING = """
+    Returns:
+
+    Example::
+
+        >>> from transformers import FlaxViTFeatureExtractor, ViTForImageClassification
+        >>> from PIL import Image
+        >>> import jax
+        >>> import requests
+
+        >>> url = 'http://images.cocodataset.org/val2017/000000039769.jpg'
+        >>> image = Image.open(requests.get(url, stream=True).raw)
+
+        >>> feature_extractor = ViTFeatureExtractor.from_pretrained('google/vit-base-patch16-224')
+        >>> model = FlaxViTForImageClassification.from_pretrained('google/vit-base-patch16-224')
+
+        >>> inputs = feature_extractor(images=image, return_tensors="jax")
+        >>> outputs = model(**inputs)
+        >>> logits = outputs.logits
+        >>> # model predicts one of the 1000 ImageNet classes
+        >>> predicted_class_idx = jax.numpy.argmax(logits, axis=-1)
+        >>> print("Predicted class:", model.config.id2label[predicted_class_idx])
+"""
+
+overwrite_call_docstring(FlaxViTForImageClassification, FLAX_VISION_CLASSIF_DOCSTRING)
+append_replace_return_docstrings(
+    FlaxViTForImageClassification, output_type=FlaxSequenceClassifierOutput, config_class=ViTConfig
+)

src/transformers/utils/dummy_flax_objects.py

@@ -405,3 +405,17 @@ class FlaxRobertaPreTrainedModel:
     @classmethod
     def from_pretrained(self, *args, **kwargs):
         requires_backends(self, ["flax"])
+
+
+class FlaxViTForImageClassification:
+    def __init__(self, *args, **kwargs):
+        requires_backends(self, ["flax"])
+
+
+class FlaxViTModel:
+    def __init__(self, *args, **kwargs):
+        requires_backends(self, ["flax"])
+
+    @classmethod
+    def from_pretrained(self, *args, **kwargs):
+        requires_backends(self, ["flax"])

tests/test_modeling_flax_vit.py

@@ -0,0 +1,240 @@
+# Copyright 2021 The HuggingFace Team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import inspect
+import unittest
+
+import numpy as np
+
+from transformers import ViTConfig, is_flax_available
+from transformers.testing_utils import require_flax, slow
+
+from .test_configuration_common import ConfigTester
+from .test_modeling_flax_common import FlaxModelTesterMixin, floats_tensor
+
+
+if is_flax_available():
+
+    import jax
+    from transformers.models.vit.modeling_flax_vit import FlaxViTForImageClassification, FlaxViTModel
+
+
+class FlaxViTModelTester(unittest.TestCase):
+    def __init__(
+        self,
+        parent,
+        batch_size=13,
+        image_size=30,
+        patch_size=2,
+        num_channels=3,
+        is_training=True,
+        use_labels=True,
+        hidden_size=32,
+        num_hidden_layers=5,
+        num_attention_heads=4,
+        intermediate_size=37,
+        hidden_act="gelu",
+        hidden_dropout_prob=0.1,
+        attention_probs_dropout_prob=0.1,
+        type_sequence_label_size=10,
+        initializer_range=0.02,
+    ):
+        self.parent = parent
+        self.batch_size = batch_size
+        self.image_size = image_size
+        self.patch_size = patch_size
+        self.num_channels = num_channels
+        self.is_training = is_training
+        self.use_labels = use_labels
+        self.hidden_size = hidden_size
+        self.num_hidden_layers = num_hidden_layers
+        self.num_attention_heads = num_attention_heads
+        self.intermediate_size = intermediate_size
+        self.hidden_act = hidden_act
+        self.hidden_dropout_prob = hidden_dropout_prob
+        self.attention_probs_dropout_prob = attention_probs_dropout_prob
+        self.type_sequence_label_size = type_sequence_label_size
+        self.initializer_range = initializer_range
+
+    def prepare_config_and_inputs(self):
+        pixel_values = floats_tensor([self.batch_size, self.num_channels, self.image_size, self.image_size])
+
+        config = ViTConfig(
+            image_size=self.image_size,
+            patch_size=self.patch_size,
+            num_channels=self.num_channels,
+            hidden_size=self.hidden_size,
+            num_hidden_layers=self.num_hidden_layers,
+            num_attention_heads=self.num_attention_heads,
+            intermediate_size=self.intermediate_size,
+            hidden_act=self.hidden_act,
+            hidden_dropout_prob=self.hidden_dropout_prob,
+            attention_probs_dropout_prob=self.attention_probs_dropout_prob,
+            is_decoder=False,
+            initializer_range=self.initializer_range,
+        )
+
+        return config, pixel_values
+
+    def create_and_check_model(self, config, pixel_values, labels):
+
+        model = FlaxViTModel(config=config)
+        result = model(pixel_values)
+        # expected sequence length = num_patches + 1 (we add 1 for the [CLS] token)
+        image_size = (self.image_size, self.image_size)
+        patch_size = (self.patch_size, self.patch_size)
+        num_patches = (image_size[1] // patch_size[1]) * (image_size[0] // patch_size[0])
+        self.parent.assertEqual(result.last_hidden_state.shape, (self.batch_size, num_patches + 1, self.hidden_size))
+
+    def prepare_config_and_inputs_for_common(self):
+        config_and_inputs = self.prepare_config_and_inputs()
+        (
+            config,
+            pixel_values,
+        ) = config_and_inputs
+        inputs_dict = {"pixel_values": pixel_values}
+        return config, inputs_dict
+
+
+@require_flax
+class FlaxViTModelTest(FlaxModelTesterMixin, unittest.TestCase):
+
+    all_model_classes = (FlaxViTModel, FlaxViTForImageClassification) if is_flax_available() else ()
+
+    def setUp(self) -> None:
+        self.model_tester = FlaxViTModelTester(self)
+        self.config_tester = ConfigTester(self, config_class=ViTConfig, has_text_modality=False, hidden_size=37)
+
+    def test_config(self):
+        self.config_tester.run_common_tests()
+
+    # We need to override this test because in ViT, the seq_len equals the number of patches + 1
+    # we compute that here
+    def test_attention_outputs(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        config.return_dict = True
+
+        num_patches = (config.image_size // config.patch_size) ** 2
+        seq_length = num_patches + 1
+
+        for model_class in self.all_model_classes:
+            inputs_dict["output_attentions"] = True
+            inputs_dict["output_hidden_states"] = False
+            model = model_class(config)
+            outputs = model(**self._prepare_for_class(inputs_dict, model_class))
+            attentions = outputs.attentions
+            self.assertEqual(len(attentions), self.model_tester.num_hidden_layers)
+
+            # check that output_attentions also work using config
+            del inputs_dict["output_attentions"]
+            config.output_attentions = True
+            model = model_class(config)
+            outputs = model(**self._prepare_for_class(inputs_dict, model_class))
+            attentions = outputs.attentions
+            self.assertEqual(len(attentions), self.model_tester.num_hidden_layers)
+
+            self.assertListEqual(
+                list(attentions[0].shape[-3:]),
+                [self.model_tester.num_attention_heads, seq_length, seq_length],
+            )
+            out_len = len(outputs)
+
+            # Check attention is always last and order is fine
+            inputs_dict["output_attentions"] = True
+            inputs_dict["output_hidden_states"] = True
+            model = model_class(config)
+            outputs = model(**self._prepare_for_class(inputs_dict, model_class))
+
+            added_hidden_states = 1
+            self.assertEqual(out_len + added_hidden_states, len(outputs))
+
+            self.assertEqual(len(attentions), self.model_tester.num_hidden_layers)
+            self.assertListEqual(
+                list(attentions[0].shape[-3:]),
+                [self.model_tester.num_attention_heads, seq_length, seq_length],
+            )
+
+    # We neeed to override this test because ViT's forward signature is different than text models.
+    def test_forward_signature(self):
+        config, _ = self.model_tester.prepare_config_and_inputs_for_common()
+
+        for model_class in self.all_model_classes:
+            model = model_class(config)
+            signature = inspect.signature(model.__call__)
+            # signature.parameters is an OrderedDict => so arg_names order is deterministic
+            arg_names = [*signature.parameters.keys()]
+
+            expected_arg_names = ["pixel_values"]
+            self.assertListEqual(arg_names[:1], expected_arg_names)
+
+    # We neeed to override this test because ViT expects pixel_values instead of input_ids
+    def test_jit_compilation(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+
+        for model_class in self.all_model_classes:
+            with self.subTest(model_class.__name__):
+                prepared_inputs_dict = self._prepare_for_class(inputs_dict, model_class)
+                model = model_class(config)
+
+                @jax.jit
+                def model_jitted(pixel_values, **kwargs):
+                    return model(pixel_values=pixel_values, **kwargs)
+
+                with self.subTest("JIT Enabled"):
+                    jitted_outputs = model_jitted(**prepared_inputs_dict).to_tuple()
+
+                with self.subTest("JIT Disabled"):
+                    with jax.disable_jit():
+                        outputs = model_jitted(**prepared_inputs_dict).to_tuple()
+
+                self.assertEqual(len(outputs), len(jitted_outputs))
+                for jitted_output, output in zip(jitted_outputs, outputs):
+                    self.assertEqual(jitted_output.shape, output.shape)
+
+    # We need to override this test because in ViT, the seq_len equals the number of patches + 1
+    # we compute that here
+    def test_hidden_states_output(self):
+        def check_hidden_states_output(inputs_dict, config, model_class):
+            model = model_class(config)
+            num_patches = (config.image_size // config.patch_size) ** 2
+            seq_length = num_patches + 1  # we add 1 for the [CLS] token
+
+            outputs = model(**self._prepare_for_class(inputs_dict, model_class))
+            hidden_states = outputs.hidden_states
+
+            self.assertEqual(len(hidden_states), self.model_tester.num_hidden_layers + 1)
+
+            self.assertListEqual(
+                list(hidden_states[0].shape[-2:]),
+                [seq_length, self.model_tester.hidden_size],
+            )
+
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+
+        for model_class in self.all_model_classes:
+            inputs_dict["output_hidden_states"] = True
+            check_hidden_states_output(inputs_dict, config, model_class)
+
+            # check that output_hidden_states also work using config
+            del inputs_dict["output_hidden_states"]
+            config.output_hidden_states = True
+
+            check_hidden_states_output(inputs_dict, config, model_class)
+
+    @slow
+    def test_model_from_pretrained(self):
+        for model_class_name in self.all_model_classes:
+            model = model_class_name.from_pretrained("google/vit-base-patch16-224")
+            outputs = model(np.ones((1, 3, 224, 224)))
+            self.assertIsNotNone(outputs)