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61 lines (52 loc) · 2.14 KB
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import jax
import flax.linen as nn
from transformers.models.bart.modeling_flax_bart import (
FlaxBartModule,
FlaxBartForConditionalGenerationModule,
FlaxBartForConditionalGeneration,
FlaxBartEncoder,
FlaxBartDecoder,
)
from transformers import BartConfig
class CustomFlaxBartModule(FlaxBartModule):
def setup(self):
# we keep shared to easily load pre-trained weights
self.shared = nn.Embed(
self.config.vocab_size,
self.config.d_model,
embedding_init=jax.nn.initializers.normal(self.config.init_std),
)
# a separate embedding is used for the decoder
self.decoder_embed = nn.Embed(
self.config.image_vocab_size + 1,
self.config.d_model,
embedding_init=jax.nn.initializers.normal(self.config.init_std),
)
self.encoder = FlaxBartEncoder(
self.config, dtype=self.dtype, embed_tokens=self.shared
)
# the decoder has a different config
# TODO: should not be needed once we have custom config/module
decoder_config = BartConfig(self.config.to_dict())
decoder_config.max_position_embeddings = (
self.config.image_length + 1 # image tokens + BOS
)
decoder_config.vocab_size = self.config.image_vocab_size + 1
self.decoder = FlaxBartDecoder(
decoder_config, dtype=self.dtype, embed_tokens=self.decoder_embed
)
class CustomFlaxBartForConditionalGenerationModule(
FlaxBartForConditionalGenerationModule
):
def setup(self):
self.model = CustomFlaxBartModule(config=self.config, dtype=self.dtype)
self.lm_head = nn.Dense(
self.config.image_vocab_size + 1, # encoded image token space + 1 for bos
use_bias=False,
kernel_init=jax.nn.initializers.normal(self.config.init_std),
)
self.final_logits_bias = self.param(
"final_logits_bias", self.bias_init, (1, self.config.image_vocab_size + 1)
)
class CustomFlaxBartForConditionalGeneration(FlaxBartForConditionalGeneration):
module_class = CustomFlaxBartForConditionalGenerationModule