240 lines
11 KiB
Python
240 lines
11 KiB
Python
import numpy as np
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import torch
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from torch import nn
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from torch.autograd import Variable
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from transformers import DetrForObjectDetection
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from .backbone import build_backbone
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from .transformer import TransformerEncoder, TransformerEncoderLayer, build_transformer
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def reparametrize(mu, logvar):
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std = logvar.div(2).exp()
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eps = Variable(std.data.new(std.size()).normal_())
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return mu + std * eps
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def get_sinusoid_encoding_table(n_position, d_hid):
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def get_position_angle_vec(position):
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return [position / np.power(10000, 2 * (hid_j // 2) / d_hid) for hid_j in range(d_hid)]
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sinusoid_table = np.array([get_position_angle_vec(pos_i) for pos_i in range(n_position)])
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sinusoid_table[:, 0::2] = np.sin(sinusoid_table[:, 0::2]) # dim 2i
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sinusoid_table[:, 1::2] = np.cos(sinusoid_table[:, 1::2]) # dim 2i+1
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return torch.FloatTensor(sinusoid_table).unsqueeze(0)
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class ActionChunkingTransformer(nn.Module):
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"""
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Action Chunking Transformer as per Learning Fine-Grained Bimanual Manipulation with Low-Cost Hardware
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(https://arxiv.org/abs/2304.13705).
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Note: In this code we use the symbols `vae_encoder`, 'encoder', `decoder`. The meanings are as follows.
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- The `vae_encoder` is, as per the literature around conditional variational auto-encoders (cVAE), the
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part of the model that encodes the target data (here, a sequence of actions), and the condition
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(here, we include the robot joint-space state as an input to the encoder).
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- The `transformer` is the cVAE's decoder. But since we have an option to train this model without the
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variational objective (in which case we drop the `vae_encoder` altogether), we don't call it the
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`vae_decoder`.
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# TODO(now): remove the following
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- The `encoder` is actually a component of the cVAE's "decoder". But we refer to it as an "encoder"
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because, in terms of the transformer with cross-attention that forms the cVAE's decoder, it is the
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"encoder" part. We drop the `vae_` prefix because we have an option to train this model without the
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variational objective (in which case we drop the `vae_encoder` altogether), and nothing about this
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model has anything to do with a VAE).
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- The `decoder` is a building block of the VAE decoder, and is just the "decoder" part of a
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transformer with cross-attention. For the same reasoning behind the naming of `encoder`, we make
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this term agnostic to the option to use a variational objective for training.
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"""
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def __init__(
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self, backbones, transformer, vae_encoder, state_dim, action_dim, horizon, camera_names, vae
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):
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"""Initializes the model.
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Parameters:
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backbones: torch module of the backbone to be used. See backbone.py
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transformer: torch module of the transformer architecture. See transformer.py
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state_dim: robot state dimension of the environment
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horizon: number of object queries, ie detection slot. This is the maximal number of objects
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DETR can detect in a single image. For COCO, we recommend 100 queries.
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Args:
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state_dim: Robot positional state dimension.
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action_dim: Action dimension.
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horizon: The number of actions to generate in one forward pass.
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vae: Whether to use the variational objective. TODO(now): Give more details.
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"""
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super().__init__()
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self.camera_names = camera_names
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self.transformer = transformer
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self.vae_encoder = vae_encoder
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self.vae = vae
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hidden_dim = transformer.d_model
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self.action_head = nn.Linear(hidden_dim, action_dim)
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self.is_pad_head = nn.Linear(hidden_dim, 1)
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# Positional embedding to be used as input to the latent vae_encoder (if applicable) and for the
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self.pos_embed = nn.Embedding(horizon, hidden_dim)
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if backbones is not None:
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self.input_proj = nn.Conv2d(backbones[0].num_channels, hidden_dim, kernel_size=1)
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self.backbones = nn.ModuleList(backbones)
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self.input_proj_robot_state = nn.Linear(state_dim, hidden_dim)
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else:
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# input_dim = 14 + 7 # robot_state + env_state
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self.input_proj_robot_state = nn.Linear(state_dim, hidden_dim)
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# TODO(rcadene): understand what is env_state, and why it needs to be 7
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self.input_proj_env_state = nn.Linear(state_dim // 2, hidden_dim)
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self.pos = torch.nn.Embedding(2, hidden_dim)
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self.backbones = None
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# vae_encoder extra parameters
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self.latent_dim = 32 # final size of latent z # TODO tune
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self.cls_embed = nn.Embedding(1, hidden_dim) # extra cls token embedding
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self.vae_encoder_action_proj = nn.Linear(14, hidden_dim) # project action to embedding
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self.vae_encoder_joint_proj = nn.Linear(14, hidden_dim) # project qpos to embedding
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self.latent_proj = nn.Linear(
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hidden_dim, self.latent_dim * 2
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) # project hidden state to latent std, var
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self.register_buffer(
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"pos_table", get_sinusoid_encoding_table(1 + 1 + horizon, hidden_dim)
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) # [CLS], qpos, a_seq
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# decoder extra parameters
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self.latent_out_proj = nn.Linear(self.latent_dim, hidden_dim) # project latent sample to embedding
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self.additional_pos_embed = nn.Embedding(
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2, hidden_dim
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) # learned position embedding for proprio and latent
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def forward(self, qpos, image, env_state, actions=None, is_pad=None):
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"""
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qpos: batch, qpos_dim
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image: batch, num_cam, channel, height, width
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env_state: None
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actions: batch, seq, action_dim
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"""
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is_training = actions is not None # train or val
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bs, _ = qpos.shape
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### Obtain latent z from action sequence
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if self.vae and is_training:
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# project action sequence to embedding dim, and concat with a CLS token
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action_embed = self.vae_encoder_action_proj(actions) # (bs, seq, hidden_dim)
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qpos_embed = self.vae_encoder_joint_proj(qpos) # (bs, hidden_dim)
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qpos_embed = torch.unsqueeze(qpos_embed, axis=1) # (bs, 1, hidden_dim)
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cls_embed = self.cls_embed.weight # (1, hidden_dim)
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cls_embed = torch.unsqueeze(cls_embed, axis=0).repeat(bs, 1, 1) # (bs, 1, hidden_dim)
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vae_encoder_input = torch.cat(
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[cls_embed, qpos_embed, action_embed], axis=1
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) # (bs, seq+1, hidden_dim)
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vae_encoder_input = vae_encoder_input.permute(1, 0, 2) # (seq+1, bs, hidden_dim)
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# do not mask cls token
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# cls_joint_is_pad = torch.full((bs, 2), False).to(qpos.device) # False: not a padding
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# is_pad = torch.cat([cls_joint_is_pad, is_pad], axis=1) # (bs, seq+1)
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# obtain position embedding
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pos_embed = self.pos_table.clone().detach()
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pos_embed = pos_embed.permute(1, 0, 2) # (seq+1, 1, hidden_dim)
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# query model
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vae_encoder_output = self.vae_encoder(vae_encoder_input, pos=pos_embed) # , src_key_padding_mask=is_pad)
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vae_encoder_output = vae_encoder_output[0] # take cls output only
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latent_info = self.latent_proj(vae_encoder_output)
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mu = latent_info[:, : self.latent_dim]
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logvar = latent_info[:, self.latent_dim :]
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latent_sample = reparametrize(mu, logvar)
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latent_input = self.latent_out_proj(latent_sample)
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else:
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mu = logvar = None
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latent_sample = torch.zeros([bs, self.latent_dim], dtype=torch.float32).to(qpos.device)
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latent_input = self.latent_out_proj(latent_sample)
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if self.backbones is not None:
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# Image observation features and position embeddings
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all_cam_features = []
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all_cam_pos = []
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for cam_id, _ in enumerate(self.camera_names):
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features, pos = self.backbones[0](image[:, cam_id]) # HARDCODED
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features = features[0] # take the last layer feature
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pos = pos[0]
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all_cam_features.append(self.input_proj(features))
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all_cam_pos.append(pos)
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# proprioception features
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proprio_input = self.input_proj_robot_state(qpos)
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# fold camera dimension into width dimension
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src = torch.cat(all_cam_features, axis=3)
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pos = torch.cat(all_cam_pos, axis=3)
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hs = self.transformer(
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src,
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None,
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self.pos_embed.weight,
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pos,
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latent_input,
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proprio_input,
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self.additional_pos_embed.weight,
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)[0]
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else:
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qpos = self.input_proj_robot_state(qpos)
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env_state = self.input_proj_env_state(env_state)
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transformer_input = torch.cat([qpos, env_state], axis=1) # seq length = 2
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hs = self.transformer(transformer_input, None, self.pos_embed.weight, self.pos.weight)[0]
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a_hat = self.action_head(hs)
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is_pad_hat = self.is_pad_head(hs)
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return a_hat, is_pad_hat, [mu, logvar]
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def mlp(input_dim, hidden_dim, output_dim, hidden_depth):
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if hidden_depth == 0:
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mods = [nn.Linear(input_dim, output_dim)]
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else:
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mods = [nn.Linear(input_dim, hidden_dim), nn.ReLU(inplace=True)]
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for _ in range(hidden_depth - 1):
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mods += [nn.Linear(hidden_dim, hidden_dim), nn.ReLU(inplace=True)]
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mods.append(nn.Linear(hidden_dim, output_dim))
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trunk = nn.Sequential(*mods)
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return trunk
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def build_vae_encoder(args):
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d_model = args.hidden_dim # 256
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dropout = args.dropout # 0.1
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nhead = args.nheads # 8
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dim_feedforward = args.dim_feedforward # 2048
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num_encoder_layers = args.enc_layers # 4 # TODO shared with VAE decoder
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normalize_before = args.pre_norm # False
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activation = "relu"
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encoder_layer = TransformerEncoderLayer(
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d_model, nhead, dim_feedforward, dropout, activation, normalize_before
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)
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encoder_norm = nn.LayerNorm(d_model) if normalize_before else None
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encoder = TransformerEncoder(encoder_layer, num_encoder_layers, encoder_norm)
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return encoder
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def build(args):
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# From state
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# backbone = None # from state for now, no need for conv nets
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# From image
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backbones = []
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backbone = build_backbone(args)
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backbones.append(backbone)
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transformer = build_transformer(args)
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vae_encoder = build_vae_encoder(args)
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model = ActionChunkingTransformer(
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backbones,
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transformer,
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vae_encoder,
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state_dim=args.state_dim,
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action_dim=args.action_dim,
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horizon=args.num_queries,
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camera_names=args.camera_names,
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vae=args.vae,
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)
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n_parameters = sum(p.numel() for p in model.parameters() if p.requires_grad)
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print("number of parameters: {:.2f}M".format(n_parameters / 1e6))
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return model
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