init diffusion
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Hanzhang Ma
171
main.ipynb
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171
main.ipynb
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Network Helper\n",
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"\n"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {},
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"outputs": [],
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"source": [
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"import torch.nn as nn\n",
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"import inspect\n",
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"import torch\n",
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"import math"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {},
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"outputs": [],
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"source": [
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"def exists(x):\n",
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" return x is not None\n",
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"\n",
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"def default(val, d):\n",
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" if exists(val):\n",
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" return val\n",
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" return d() if inspect.isfunction(d) else d\n",
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"\n",
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"class Residual(nn.Module):\n",
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" def __init__(self, fn):\n",
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" super().__init__()\n",
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" self.fn = fn\n",
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"\n",
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" def forward(self, x, *args, **kwargs):\n",
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" return self.fn(x, *args, **kwargs) + x\n",
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"\n",
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"# 上采样(反卷积)\n",
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"def Upsample(dim):\n",
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" return nn.ConvTranspose2d(dim, dim, 4, 2, 1)\n",
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"\n",
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"def Downsample(dim):\n",
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" return nn.Conv2d(dim, dim, 4, 2 ,1)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Positional embedding\n",
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"\n",
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"目的是让网络知道\n",
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"当前是哪一个step. \n",
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"ddpm采用正弦位置编码\n",
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"\n",
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"输入是shape为(batch_size, 1)的tensor, batch中每一个sample所处的t,并且将这个tensor转换为shape为(batch_size, dim)的tensor.\n",
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"这个tensor会被加到每一个残差模块中.\n",
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"\n",
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"总之就是将$t$编码为embedding,和原本的输入一起进入网络,让网络“知道”当前的输入属于哪个step"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"class SinusolidalPositionEmbedding(nn.Module):\n",
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" def __init__(self, dim):\n",
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" super().__init__()\n",
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" self.dim = dim\n",
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"\n",
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" def forward(self, time):\n",
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" device = time.device\n",
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" half_dim = self.dim // 2\n",
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" embeddings = math.log(10000) / (half_dim - 1)\n",
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" embeddings = torch.exp(torch.arange(half_dim, device=device) * -embeddings)\n",
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" embeddings = time[:, :, None] * embeddings[None, None, :]\n",
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" embeddings = torch.cat((embeddings.sin(), embeddings.cos()), dim=-1)\n",
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" return embeddings\n",
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" "
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## ResNet/ConvNeXT block"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"class Block(nn.Module):\n",
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" def __init__(self, dim, dim_out, groups = 8):\n",
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" super().__init__()\n",
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" self.proj = nn.Conv2d(dim, dim_out, 3, padding=1)\n",
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" self.norm = nn.GroupNorm(groups, dim_out)\n",
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" self.act = nn.SiLU()\n",
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" \n",
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" def forward(self, x, scale_shift = None):\n",
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" x = self.proj(x)\n",
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" x = self.norm(x)\n",
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"\n",
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" if exists(scale_shift):\n",
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" scale, shift = scale_shift\n",
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" x = x * (scale + 1) + shift\n",
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"\n",
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" x = self.act(x)\n",
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" return x\n",
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"\n",
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"class ResnetBlock(nn.Module):\n",
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" def __init__(self, dim, dim_out, *, time_emb_dim = None, groups = 8):\n",
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" super().__init__()\n",
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" self.mlp = (\n",
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" nn.Sequential(\n",
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" nn.SiLU(), \n",
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" nn.Linear(time_emb_dim, dim_out)\n",
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" )\n",
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" if exists(time_emb_dim) else None\n",
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" )\n",
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" self.block1 = Block(dim, dim_out, groups=groups)\n",
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" self.block2 = Block(dim_out, dim_out=dim_out, groups=groups)\n",
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" self.res_conv = nn.Conv2d(dim, dim_out, 1) if dim != dim_out else nn.Identity()\n",
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" \n",
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" def forward(self, x, time_emb = None):\n",
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" h = self.block1(x)\n",
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"\n",
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" if exists(self.mlp) and exists(time_emb):\n",
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" time_emb = self.mlp(time_emb)\n",
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" h = rearrange(time_emb, 'b n -> b () n') + h\n",
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"\n",
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" h = self.block2(h)\n",
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" return h + self.res_conv(x)\n",
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" \n",
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" "
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "arch2vec39",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.6.13"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}
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