from typing import Optional, Tuple, Union import copy import torch import torch.nn as nn import torch.nn.functional as F from transformers import PreTrainedModel from transformers.modeling_outputs import ( BaseModelOutputWithPastAndCrossAttentions, Seq2SeqLMOutput, BaseModelOutput, ) from transformers.utils import logging, is_torch_fx_proxy from .configuration_openbt5 import OpenBT5Config logger = logging.get_logger(__name__) # Copied from transformers.models.gptj.modeling_gptj.create_sinusoidal_positions def create_sinusoidal_positions(num_pos: int, dim: int) -> torch.Tensor: inv_freq = 1.0 / (10000 ** (torch.arange(0, dim, 2) / dim)) sinusoid_inp = torch.einsum("i , j -> i j", torch.arange(num_pos, dtype=torch.float), inv_freq).float() return torch.cat((torch.sin(sinusoid_inp), torch.cos(sinusoid_inp)), dim=1) def rotate_half(x) -> torch.Tensor: x1, x2 = x[..., : x.shape[-1] // 2], x[..., x.shape[-1] // 2 :] return torch.cat((-x2, x1), dim=-1) def apply_rotary_pos_emb(tensor: torch.Tensor, sin: torch.Tensor, cos: torch.Tensor) -> torch.Tensor: sin = torch.cat((sin, sin), dim=-1).to(tensor.device)[:, :, None, :] cos = torch.cat((cos, cos), dim=-1).to(tensor.device)[:, :, None, :] return (tensor * cos) + (rotate_half(tensor) * sin) class SwiGLUMLP(nn.Module): def __init__(self, config): super().__init__() multiple_of: int = 256 # make SwiGLU hidden layer size multiple of large power of 2 hidden_size = config.hidden_size ffn_hidden_size = int(2 * config.ffn_hidden_size / 3) ffn_hidden_size = multiple_of * ((ffn_hidden_size + multiple_of - 1) // multiple_of) self.ffn_hidden_size = ffn_hidden_size self.fc_in = nn.Linear(hidden_size, 2 * ffn_hidden_size, bias=config.add_ffn_bias) self.fc_out = nn.Linear(ffn_hidden_size, hidden_size, bias=config.add_ffn_bias) def swiglu(x): x = torch.chunk(x, 2, dim=-1) return F.silu(x[0]) * x[1] self.act_func = swiglu def forward(self, hidden_states: Optional[torch.FloatTensor]) -> torch.FloatTensor: hidden_states = self.fc_in(hidden_states) hidden_states = self.act_func(hidden_states) hidden_states = self.fc_out(hidden_states) return hidden_states class OpenBT5Attention(nn.Module): def __init__(self, config, attn_type='self'): super().__init__() self.attn_type = attn_type self.is_decoder = config.is_decoder self.hidden_size = config.hidden_size self.num_heads = config.num_heads self.kv_channels = config.kv_channels self.proj_size = self.kv_channels * self.num_heads self.dropout = config.attention_dropout self.scale_attn = torch.sqrt(torch.tensor(self.kv_channels, dtype=torch.float32)) if self.attn_type == 'self': self.qkv = nn.Linear(self.hidden_size, 3 * self.proj_size, bias=config.add_qkv_bias) else: assert self.attn_type == 'cross' self.q = nn.Linear(self.hidden_size, self.proj_size, bias=config.add_qkv_bias) self.kv = nn.Linear(self.hidden_size, 2 * self.proj_size, bias=config.add_qkv_bias) self.rotary_embedding = create_sinusoidal_positions( num_pos=config.max_seq_length, dim=self.kv_channels, ) self.o = nn.Linear(self.proj_size, self.hidden_size, bias=config.add_qkv_bias) def forward( self, hidden_states: Optional[torch.FloatTensor], attention_mask: Optional[torch.FloatTensor] = None, key_value_states: Optional[torch.FloatTensor] = None, past_key_value: Optional[Tuple[torch.Tensor]] = None, layer_head_mask: Optional[Tuple[torch.Tensor]] = None, position_ids:Optional[torch.LongTensor] = None, use_cache: Optional[bool] = False, output_attentions: Optional[bool] = False, ): # input is (batch_size, seq_length, hidden_size) batch_size, seq_length = hidden_states.shape[:2] if past_key_value is not None: if len(past_key_value) != 2: raise ValueError( f"past_key_value should have 2 past states: keys and values. Got { len(past_key_value)} past states" ) if self.rotary_embedding.device != position_ids.device: self.rotary_embedding = self.rotary_embedding.to(position_ids.device) if self.attn_type == 'self': mixed_qkv_states = self.qkv(hidden_states) new_tensor_shape = mixed_qkv_states.size()[:-1] + (self.num_heads, 3 * self.kv_channels) mixed_qkv_states = mixed_qkv_states.view(*new_tensor_shape) query_states, key_states, value_states = torch.chunk(mixed_qkv_states, 3, dim=-1) # rotary position embedding sincos = self.rotary_embedding[position_ids] sin, cos = torch.chunk(sincos, 2, dim=-1) query_states = apply_rotary_pos_emb(query_states, sin, cos) key_states = apply_rotary_pos_emb(key_states, sin, cos) # reshape to (batch_size, num_head, seq_length, kv_channels) query_states = query_states.transpose(1, 2) key_states = key_states.transpose(1, 2) value_states = value_states.transpose(1, 2) if past_key_value is not None: past_key_states, past_value_states = past_key_value key_states = torch.cat([past_key_states, key_states], dim=-2) value_states = torch.cat([past_value_states, value_states], dim=-2) else: assert self.attn_type == 'cross' query_states = self.q(hidden_states) new_tensor_shape = query_states.size()[:-1] + (self.num_heads, self.kv_channels) query_states = query_states.view(*new_tensor_shape) # reshape to (batch_size, num_head, seq_length, kv_channels) query_states = query_states.transpose(1, 2) if past_key_value is None: mixed_kv_states = self.kv(key_value_states) new_tensor_shape = mixed_kv_states.size()[:-1] + (self.num_heads, 2 * self.kv_channels) mixed_kv_states = mixed_kv_states.view(*new_tensor_shape) key_states, value_states = torch.chunk(mixed_kv_states, 2, dim=-1) # reshape to (batch_size, num_head, seq_length, kv_channels) key_states = key_states.transpose(1, 2) value_states = value_states.transpose(1, 2) else: key_states, value_states = past_key_value # compute attention score query_states = query_states.to(torch.float32) key_states = key_states.to(torch.float32) attn_scores = torch.matmul(query_states, key_states.transpose(-1, -2)) / self.scale_attn attn_scores = attn_scores.masked_fill_(attention_mask, -10000.0) attn_weights = F.softmax(attn_scores, dim=-1).type_as(attn_scores) attn_weights = nn.functional.dropout(attn_weights, p=self.dropout, training=self.training) attn_weights = attn_weights.to(value_states.dtype) # Mask heads if we want to if layer_head_mask is not None: attn_weights = attn_weights * layer_head_mask attn_output = torch.matmul(attn_weights, value_states) attn_output = attn_output.transpose(1, 2).contiguous().view(batch_size, -1, self.proj_size) attn_output = self.o(attn_output) present_key_value_state = (key_states, value_states) if (self.is_decoder and use_cache) else None outputs = (attn_output, present_key_value_state) if output_attentions: outputs += (attn_weights,) return outputs class OpenBT5Block(nn.Module): def __init__(self, config) -> None: super().__init__() self.is_decoder = config.is_decoder self.dropout = config.hidden_dropout self.input_layernorm = nn.LayerNorm(config.hidden_size) self.self_attn = OpenBT5Attention(config, attn_type='self') self.post_attn_layernorm = nn.LayerNorm(config.hidden_size) if self.is_decoder: self.inter_attn = OpenBT5Attention(config, attn_type='cross') self.post_inter_attn_layernorm = nn.LayerNorm(config.hidden_size) self.mlp = SwiGLUMLP(config) def forward( self, hidden_states=None, attention_mask=None, position_ids=None, encoder_hidden_states=None, encoder_attention_mask=None, layer_head_mask=None, cross_attn_layer_head_mask=None, past_key_value=None, use_cache=False, output_attentions=False, ): if past_key_value is not None: if not self.is_decoder: raise ValueError("`past_key_values` is passed to the encoder. Please make sure this is intended.") expected_num_past_key_values = 2 if encoder_hidden_states is None else 4 if len(past_key_value) != expected_num_past_key_values: raise ValueError( f"There should be {expected_num_past_key_values} past states. " f"{'2 (past / key) for cross attention. ' if expected_num_past_key_values == 4 else ''}" f"Got {len(past_key_value)} past key / value states" ) self_attn_past_key_value = past_key_value[:2] cross_attn_past_key_value = past_key_value[2:] else: self_attn_past_key_value, cross_attn_past_key_value = None, None # Layer norm at the beginning of the transformer layer. layernorm_output = self.input_layernorm(hidden_states) # Self attention. attn_outputs = self.self_attn( layernorm_output, attention_mask=attention_mask, position_ids=position_ids, layer_head_mask=layer_head_mask, past_key_value=self_attn_past_key_value, use_cache=use_cache, output_attentions=output_attentions, ) attn_output, present_key_value_state = attn_outputs[:2] attn_weights = attn_outputs[2:] residual = hidden_states # Layer norm post the self attention. attn_output = nn.functional.dropout(attn_output, p=self.dropout, training=self.training) layernorm_input = residual + attn_output layernorm_output = self.post_attn_layernorm(layernorm_input) if self.is_decoder: assert encoder_hidden_states is not None attn_outputs = self.inter_attn( layernorm_output, attention_mask=encoder_attention_mask, key_value_states=encoder_hidden_states, position_ids=position_ids, layer_head_mask=cross_attn_layer_head_mask, past_key_value=cross_attn_past_key_value, use_cache=use_cache, output_attentions=output_attentions, ) attn_output = attn_outputs[0] attn_output = nn.functional.dropout(attn_output, p=self.dropout, training=self.training) # residual connection residual = layernorm_input layernorm_input = residual + attn_output layernorm_output = self.post_inter_attn_layernorm(layernorm_input) # Combine self attn and cross attn key value states if present_key_value_state is not None: present_key_value_state += attn_outputs[1] attn_weights += attn_outputs[2:] # MLP. mlp_output = self.mlp(layernorm_output) mlp_output = nn.functional.dropout(mlp_output, p=self.dropout, training=self.training) # Second residual connection. residual = layernorm_input output = residual + mlp_output outputs = (output,) if use_cache: outputs += (present_key_value_state,) + attn_weights else: outputs += attn_weights return outputs class OpenBT5PreTrainedModel(PreTrainedModel): config_class = OpenBT5Config base_model_prefix = "transformer" _no_split_modules = ["OpenBT5Block"] def _set_gradient_checkpointing(self, module, value=False): if isinstance(module, (OpenBT5Attention, OpenBT5Stack)): module.gradient_checkpointing = value def _init_weights(self, module): """Initialize the weights""" factor = self.config.initializer_factor if isinstance(module, nn.LayerNorm): module.weight.data.fill_(1.0) module.bias.data.zero_() elif isinstance(module, OpenBT5ForConditionalGeneration): module.shared_embedding.weight.data.normal_(mean=0.0, std=factor * 1.0) if hasattr(module, "lm_head") and not self.config.tie_word_embeddings: module.lm_head.weight.data.normal_(mean=0.0, std=factor * 1.0) elif isinstance(module, SwiGLUMLP): module.fc_in.weight.data.normal_(mean=0.0, std=factor * ((self.config.hidden_size) ** -0.5)) if hasattr(module.fc_in, "bias") and module.fc_in.bias is not None: module.fc_in.bias.data.zero_() module.fc_out.weight.data.normal_(mean=0.0, std=factor * ((module.ffn_hidden_size) ** -0.5)) if hasattr(module.fc_out, "bias") and module.fc_out.bias is not None: module.fc_out.bias.data.zero_() elif isinstance(module, OpenBT5Attention): hidden_size = self.config.hidden_size kv_channels = self.config.kv_channels n_heads = self.config.num_heads if module.attn_type == 'self': module.qkv.weight.data[:n_heads * kv_channels].normal_(mean=0.0, std=factor * ((hidden_size * kv_channels) ** -0.5)) module.qkv.weight.data[n_heads * kv_channels:].normal_(mean=0.0, std=factor * (hidden_size ** -0.5)) else: module.q.weight.data.normal_(mean=0.0, std=factor * ((hidden_size * kv_channels) ** -0.5)) module.kv.weight.data.normal_(mean=0.0, std=factor * (hidden_size ** -0.5)) module.o.weight.data.normal_(mean=0.0, std=factor * ((n_heads * kv_channels) ** -0.5)) def _shift_right(self, input_ids): decoder_start_token_id = self.config.decoder_start_token_id pad_token_id = self.config.pad_token_id if decoder_start_token_id is None: raise ValueError( "self.model.config.decoder_start_token_id has to be defined. In T5 it is usually set to the pad_token_id." "See T5 docs for more information." ) # shift inputs to the right if is_torch_fx_proxy(input_ids): # Item assignment is not supported natively for proxies. shifted_input_ids = torch.full(input_ids.shape[:-1] + (1,), decoder_start_token_id) shifted_input_ids = torch.cat([shifted_input_ids, input_ids[..., :-1]], dim=-1) else: shifted_input_ids = input_ids.new_zeros(input_ids.shape) shifted_input_ids[..., 1:] = input_ids[..., :-1].clone() shifted_input_ids[..., 0] = decoder_start_token_id if pad_token_id is None: raise ValueError("self.model.config.pad_token_id has to be defined.") # replace possible -100 values in labels by `pad_token_id` shifted_input_ids.masked_fill_(shifted_input_ids == -100, pad_token_id) return shifted_input_ids class OpenBT5Stack(OpenBT5PreTrainedModel): def __init__(self, config, embed_tokens): super().__init__(config) self.embed_tokens = embed_tokens self.is_decoder = config.is_decoder self.block = nn.ModuleList( [OpenBT5Block(config) for _ in range(config.num_layers)] ) self.final_layernorm = nn.LayerNorm(config.hidden_size) def forward( self, input_ids=None, attention_mask=None, encoder_hidden_states=None, encoder_attention_mask=None, inputs_embeds=None, head_mask=None, cross_attn_head_mask=None, past_key_values=None, use_cache=None, output_attentions=None, output_hidden_states=None, return_dict=None, ): use_cache = use_cache if use_cache is not None else self.config.use_cache 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.use_return_dict # get batch size and seq_length if input_ids is not None and inputs_embeds is not None: raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time") elif input_ids is not None: input_shape = input_ids.size() input_ids = input_ids.view(-1, input_shape[-1]) elif inputs_embeds is not None: input_shape = inputs_embeds.size()[:-1] else: raise ValueError("You have to specify either input_ids or inputs_embeds") batch_size, seq_length = input_shape device = input_ids.device if input_ids is not None else inputs_embeds.device # required mask seq length can be calculated via length of past if past_key_values is None: past_length = 0 past_key_values = [None] * len(self.block) else: past_length = past_key_values[0][0].size(-2) cur_length = past_length + seq_length # position ids position_ids = torch.arange(past_length, cur_length, dtype=torch.long, device=device) position_ids = position_ids.unsqueeze(0).view(-1, seq_length) # Attention mask if attention_mask is None: attention_mask = torch.ones(batch_size, seq_length, device=device) # get extended self-attention mask if self.is_decoder: if len(attention_mask.shape) == 2: seq_ids = torch.arange(seq_length, device=device) causal_mask = seq_ids[None, None, :].repeat(batch_size, seq_length, 1) <= seq_ids[None, :, None] causal_mask = causal_mask.to(attention_mask.dtype) extended_attention_mask = causal_mask[:, None, :, :] * attention_mask[:, None, None, :] elif len(attention_mask.shape) == 3: extended_attention_mask = attention_mask[:, None, :, :] else: raise ValueError else: extended_attention_mask = attention_mask[:, None, None, :] extended_attention_mask = extended_attention_mask < 0.5 # get extended self-attention mask # here we replace encoder_decoder_attention_mask with encoder_attention_mask if self.is_decoder and encoder_hidden_states is not None: if encoder_attention_mask is None: encoder_seq_length = encoder_hidden_states.shape[1] encoder_attention_mask = torch.ones( batch_size, encoder_seq_length, device=device, dtype=torch.long ) extended_encoder_attention_mask = encoder_attention_mask[:, None, None, :] extended_encoder_attention_mask = extended_encoder_attention_mask < 0.5 else: extended_encoder_attention_mask = None # input embeddings if inputs_embeds is None: inputs_embeds = self.embed_tokens(input_ids) # Prepare head mask if needed head_mask = self.get_head_mask(head_mask, self.config.num_layers) cross_attn_head_mask = self.get_head_mask(cross_attn_head_mask, self.config.num_layers) present_key_value_states = () if use_cache else None all_hidden_states = () if output_hidden_states else None all_attentions = () if output_attentions else None all_cross_attentions = () if (output_attentions and self.is_decoder) else None hidden_states = inputs_embeds for i, (layer_module, past_key_value) in enumerate(zip(self.block, past_key_values)): layer_head_mask = head_mask[i] cross_attn_layer_head_mask = cross_attn_head_mask[i] if output_hidden_states: all_hidden_states += (hidden_states,) layer_outputs = layer_module( hidden_states, attention_mask=extended_attention_mask, position_ids=position_ids, encoder_hidden_states=encoder_hidden_states, encoder_attention_mask=extended_encoder_attention_mask, layer_head_mask=layer_head_mask, cross_attn_layer_head_mask=cross_attn_layer_head_mask, past_key_value=past_key_value, use_cache=use_cache, output_attentions=output_attentions, ) # layer_outputs is a tuple with: # hidden-states, key-value-states, (self-attention weights), (cross-attention weights) if use_cache is False: layer_outputs = layer_outputs[:1] + (None,) + layer_outputs[1:] hidden_states, present_key_value_state = layer_outputs[:2] if use_cache: present_key_value_states += (present_key_value_state,) if output_attentions: all_attentions = all_attentions + (layer_outputs[2],) if self.is_decoder: all_cross_attentions = all_cross_attentions + (layer_outputs[3],) hidden_states = self.final_layernorm(hidden_states) if output_hidden_states: all_hidden_states += (hidden_states,) if not return_dict: return tuple( v for v in [ hidden_states, present_key_value_states, all_hidden_states, all_attentions, all_cross_attentions, ] if v is not None ) return BaseModelOutputWithPastAndCrossAttentions( last_hidden_state=hidden_states, past_key_values=present_key_value_states, hidden_states=all_hidden_states, attentions=all_attentions, cross_attentions=all_cross_attentions, ) class OpenBT5ForConditionalGeneration(OpenBT5PreTrainedModel): _keys_to_ignore_on_load_missing = [ r"encoder.embed_tokens.weight", r"decoder.embed_tokens.weight", ] def __init__(self, config): super().__init__(config) self.shared_embedding = nn.Embedding(config.vocab_size, config.hidden_size) self.hidden_size = config.hidden_size encoder_config = copy.deepcopy(config) encoder_config.is_decoder = False encoder_config.use_cache = False encoder_config.is_encoder_decoder = False self.encoder = OpenBT5Stack(encoder_config, self.shared_embedding) decoder_config = copy.deepcopy(config) decoder_config.is_decoder = True decoder_config.is_encoder_decoder = False decoder_config.num_layers = config.num_decoder_layers decoder_config.max_seq_length = config.decoder_max_seq_length self.decoder = OpenBT5Stack(decoder_config, self.shared_embedding) self.lm_head = nn.Linear(config.hidden_size, config.vocab_size, bias=config.add_lm_head_bias) # Initialize weights and apply final processing self.post_init() # Model parallel self.model_parallel = False self.device_map = None def get_input_embeddings(self): return self.shared_embedding def set_input_embeddings(self, new_embeddings): self.shared_embedding = new_embeddings self.encoder.set_input_embeddings(new_embeddings) self.decoder.set_input_embeddings(new_embeddings) def set_output_embeddings(self, new_embeddings): self.lm_head = new_embeddings def get_output_embeddings(self): return self.lm_head def get_encoder(self): return self.encoder def get_decoder(self): return self.decoder def forward( self, input_ids: Optional[torch.LongTensor] = None, attention_mask: Optional[torch.FloatTensor] = None, decoder_input_ids: Optional[torch.LongTensor] = None, decoder_attention_mask: Optional[torch.BoolTensor] = None, head_mask: Optional[torch.FloatTensor] = None, decoder_head_mask: Optional[torch.FloatTensor] = None, cross_attn_head_mask: Optional[torch.Tensor] = None, encoder_outputs: Optional[Tuple[Tuple[torch.FloatTensor]]] = None, past_key_values: Optional[Tuple[Tuple[torch.FloatTensor]]] = None, inputs_embeds: Optional[torch.Tensor] = None, decoder_inputs_embeds: Optional[torch.Tensor] = None, labels: Optional[torch.LongTensor] = None, use_cache: Optional[bool] = None, output_attentions: Optional[bool] = None, output_hidden_states: Optional[bool] = None, return_dict: Optional[bool] = None, ) -> Union[Tuple[torch.FloatTensor], Seq2SeqLMOutput]: use_cache = use_cache if use_cache is not None else self.config.use_cache return_dict = return_dict if return_dict is not None else self.config.use_return_dict # Encode if needed (training, first prediction pass) if encoder_outputs is None: encoder_outputs = self.encoder( input_ids=input_ids, attention_mask=attention_mask, inputs_embeds=inputs_embeds, head_mask=head_mask, output_attentions=output_attentions, output_hidden_states=output_hidden_states, return_dict=return_dict, ) elif return_dict and not isinstance(encoder_outputs, BaseModelOutput): encoder_outputs = BaseModelOutput( last_hidden_state=encoder_outputs[0], hidden_states=encoder_outputs[1] if len(encoder_outputs) > 1 else None, attentions=encoder_outputs[2] if len(encoder_outputs) > 2 else None,\ ) hidden_states = encoder_outputs[0] if labels is not None and decoder_input_ids is None and decoder_inputs_embeds is None: # get decoder inputs from shifting lm labels to the right decoder_input_ids = self._shift_right(labels) # Decode decoder_outputs = self.decoder( input_ids=decoder_input_ids, attention_mask=decoder_attention_mask, inputs_embeds=decoder_inputs_embeds, past_key_values=past_key_values, encoder_hidden_states=hidden_states, encoder_attention_mask=attention_mask, head_mask=decoder_head_mask, cross_attn_head_mask=cross_attn_head_mask, use_cache=use_cache, output_attentions=output_attentions, output_hidden_states=output_hidden_states, return_dict=return_dict, ) sequence_output = decoder_outputs[0] # share embedding and softmax embedding if self.config.tie_word_embeddings: # Rescale output before projecting on vocab sequence_output = sequence_output * (self.hidden_size ** -0.5) lm_logits = self.lm_head(sequence_output).to(torch.float32) loss = None if labels is not None: loss_fct = nn.CrossEntropyLoss(ignore_index=-100) # move labels to correct device to enable PP labels = labels.to(lm_logits.device) loss = loss_fct(lm_logits.view(-1, lm_logits.size(-1)), labels.view(-1)) loss = loss.to(hidden_states.dtype) if not return_dict: output = (lm_logits,) + decoder_outputs[1:] + encoder_outputs return ((loss,) + output) if loss is not None else output return Seq2SeqLMOutput( loss=loss, logits=lm_logits, past_key_values=decoder_outputs.past_key_values, decoder_hidden_states=decoder_outputs.hidden_states, decoder_attentions=decoder_outputs.attentions, cross_attentions=decoder_outputs.cross_attentions, encoder_last_hidden_state=encoder_outputs.last_hidden_state, encoder_hidden_states=encoder_outputs.hidden_states, encoder_attentions=encoder_outputs.attentions, ) def prepare_inputs_for_generation( self, input_ids, past_key_values=None, attention_mask=None, head_mask=None, decoder_head_mask=None, decoder_attention_mask=None, cross_attn_head_mask=None, use_cache=None, encoder_outputs=None, **kwargs, ): # cut decoder_input_ids if past is used if past_key_values is not None: input_ids = input_ids[:, -1:] return { "decoder_input_ids": input_ids, "past_key_values": past_key_values, "encoder_outputs": encoder_outputs, "attention_mask": attention_mask, "head_mask": head_mask, "decoder_head_mask": decoder_head_mask, "decoder_attention_mask": decoder_attention_mask, "cross_attn_head_mask": cross_attn_head_mask, "use_cache": use_cache, } def prepare_decoder_input_ids_from_labels(self, labels: torch.Tensor): return self._shift_right(labels) def _reorder_cache(self, past_key_values, beam_idx): # if decoder past is not included in output # speedy decoding is disabled and no need to reorder if past_key_values is None: logger.warning("You might want to consider setting `use_cache=True` to speed up decoding") return past_key_values reordered_decoder_past = () for layer_past_states in past_key_values: # get the correct batch idx from layer past batch dim # batch dim of `past` is at 2nd position reordered_layer_past_states = () for layer_past_state in layer_past_states: # need to set correct `past` for each of the four key / value states reordered_layer_past_states = reordered_layer_past_states + ( layer_past_state.index_select(0, beam_idx.to(layer_past_state.device)), ) if reordered_layer_past_states[0].shape != layer_past_states[0].shape: raise ValueError( f"reordered_layer_past_states[0] shape {reordered_layer_past_states[0].shape} and layer_past_states[0] shape {layer_past_states[0].shape} mismatched" ) if len(reordered_layer_past_states) != len(layer_past_states): raise ValueError( f"length of reordered_layer_past_states {len(reordered_layer_past_states)} and length of layer_past_states {len(layer_past_states)} mismatched" ) reordered_decoder_past = reordered_decoder_past + (reordered_layer_past_states,) return reordered_decoder_past