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| # ------------------------------------------------------------------------ | |
| # Modified from MoE-LLaVA(https://github.com/PKU-YuanGroup/MoE-LLaVA) | |
| # ------------------------------------------------------------------------ | |
| from typing import List, Optional, Tuple, Union | |
| import torch | |
| import torch.nn as nn | |
| from torch.nn import CrossEntropyLoss | |
| from transformers.modeling_outputs import CausalLMOutputWithPast | |
| from dataclasses import dataclass | |
| from einops import rearrange, repeat, reduce, pack, unpack | |
| from transformers.utils import ModelOutput | |
| from transformers.activations import ACT2FN | |
| def MixtralDecoderLayerMOEBlock_forward(self): | |
| def forward(hidden_states: torch.Tensor): | |
| batch_size, sequence_length, hidden_dim = hidden_states.shape | |
| hidden_states = hidden_states.view(-1, hidden_dim) | |
| # router_logits: (batch * sequence_length, n_experts) | |
| router_logits = self.gate(hidden_states) | |
| router_z_loss = torch.logsumexp(router_logits, dim = -1) | |
| router_z_loss = torch.square(router_z_loss) | |
| router_z_loss = router_z_loss.mean() | |
| routing_weights = nn.functional.softmax(router_logits, dim=1, dtype=torch.float) | |
| density_1_proxy = reduce(routing_weights, '... n e -> ... e', 'mean') | |
| routing_weights, selected_experts = torch.topk(routing_weights, self.top_k, dim=-1) | |
| one_hot_gate_indices = nn.functional.one_hot(rearrange(selected_experts, '... k -> k ...'), self.num_experts).float()[0] | |
| density_1 = reduce(one_hot_gate_indices, '... n e -> ... e', 'mean') | |
| balance_loss = (density_1_proxy * density_1).mean() * float(self.num_experts ** 2) | |
| routing_weights /= routing_weights.sum(dim=-1, keepdim=True) | |
| # we cast back to the input dtype | |
| routing_weights = routing_weights.to(hidden_states.dtype) | |
| final_hidden_states = torch.zeros( | |
| (batch_size * sequence_length, hidden_dim), dtype=hidden_states.dtype, device=hidden_states.device | |
| ) | |
| # One hot encode the selected experts to create an expert mask | |
| # this will be used to easily index which expert is going to be sollicitated | |
| expert_mask = nn.functional.one_hot(selected_experts, num_classes=self.num_experts).permute(2, 1, 0) | |
| # Loop over all available experts in the model and perform the computation on each expert | |
| for expert_idx in range(self.num_experts): | |
| expert_layer = self.experts[expert_idx] | |
| idx, top_x = torch.where(expert_mask[expert_idx]) | |
| if top_x.shape[0] == 0: | |
| continue | |
| # in torch it is faster to index using lists than torch tensors | |
| top_x_list = top_x.tolist() | |
| idx_list = idx.tolist() | |
| # Index the correct hidden states and compute the expert hidden state for | |
| # the current expert. We need to make sure to multiply the output hidden | |
| # states by `routing_weights` on the corresponding tokens (top-1 and top-2) | |
| current_state = hidden_states[None, top_x_list].reshape(-1, hidden_dim) | |
| current_hidden_states = expert_layer(current_state) * routing_weights[top_x_list, idx_list, None] | |
| # However `index_add_` only support torch tensors for indexing so we'll use | |
| # the `top_x` tensor here. | |
| final_hidden_states.index_add_(0, top_x, current_hidden_states.to(hidden_states.dtype)) | |
| final_hidden_states = final_hidden_states.reshape(batch_size, sequence_length, hidden_dim) | |
| return final_hidden_states, (balance_loss, router_z_loss) | |
| return forward | |
| class SMoECausalLMOutputWithPast(ModelOutput): | |
| loss: Optional[torch.FloatTensor] = None | |
| logits: torch.FloatTensor = None | |
| past_key_values: Optional[Tuple[Tuple[torch.FloatTensor]]] = None | |
| hidden_states: Optional[Tuple[torch.FloatTensor]] = None | |
| attentions: Optional[Tuple[torch.FloatTensor]] = None | |