576 lines
17 KiB
Plaintext
576 lines
17 KiB
Plaintext
{
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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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"id": "NXTSugt6ieXh"
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},
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"source": [
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"## 训练 CBoW 模型\n",
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"\n",
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"本笔记本是 [AI for Beginners Curriculum](http://aka.ms/ai-beginners) 的一部分\n",
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"\n",
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"在这个例子中，我们将学习如何训练 CBoW 语言模型，以获得我们自己的 Word2Vec 嵌入空间。我们将使用 AG News 数据集作为文本来源。\n"
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]
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},
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{
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"cell_type": "code",
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"source": [
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"import torch\n",
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"import torchtext\n",
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"import os\n",
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"import collections\n",
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"import builtins\n",
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"import random\n",
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"import numpy as np"
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],
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"metadata": {
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"id": "q-UiiJUKaxHj"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "code",
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"source": [
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"device = torch.device(\"cuda\" if torch.cuda.is_available() else \"cpu\")"
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],
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"metadata": {
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"id": "TFbR8CZaTZ1q"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "markdown",
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"source": [
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"首先，让我们加载数据集并定义分词器和词汇表。我们将 `vocab_size` 设置为 5000 以稍微限制计算量。\n"
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],
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"metadata": {
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"id": "HIwC7lI5T-ov"
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}
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},
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{
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"cell_type": "code",
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"source": [
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"def load_dataset(ngrams = 1, min_freq = 1, vocab_size = 5000 , lines_cnt = 500):\n",
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" tokenizer = torchtext.data.utils.get_tokenizer('basic_english')\n",
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" print(\"Loading dataset...\")\n",
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" test_dataset, train_dataset = torchtext.datasets.AG_NEWS(root='./data')\n",
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" train_dataset = list(train_dataset)\n",
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" test_dataset = list(test_dataset)\n",
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" classes = ['World', 'Sports', 'Business', 'Sci/Tech']\n",
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" print('Building vocab...')\n",
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" counter = collections.Counter()\n",
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" for i, (_, line) in enumerate(train_dataset):\n",
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" counter.update(torchtext.data.utils.ngrams_iterator(tokenizer(line),ngrams=ngrams))\n",
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" if i == lines_cnt:\n",
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" break\n",
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" vocab = torchtext.vocab.Vocab(collections.Counter(dict(counter.most_common(vocab_size))), min_freq=min_freq)\n",
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" return train_dataset, test_dataset, classes, vocab, tokenizer"
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],
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"metadata": {
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"id": "wdZuygtgiuLG"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "code",
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"source": [
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"train_dataset, test_dataset, _, vocab, tokenizer = load_dataset()"
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],
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"metadata": {
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"colab": {
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"base_uri": "https://localhost:8080/"
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},
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"id": "4d1nU1gsivGu",
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"outputId": "949fe272-ae0e-49f5-c373-6703458b3a74"
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},
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"execution_count": null,
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"Loading dataset...\n",
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"Building vocab...\n"
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]
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}
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]
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},
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{
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"cell_type": "code",
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"source": [
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"def encode(x, vocabulary, tokenizer = tokenizer):\n",
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" return [vocabulary[s] for s in tokenizer(x)]"
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],
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"metadata": {
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"id": "1XDYNhG8ToFV"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"id": "LIlQk6_PaHVY"
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},
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"source": [
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"## CBoW 模型\n",
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"\n",
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"CBoW 通过 $2N$ 个邻近词来预测一个单词。例如，当 $N=1$ 时，我们可以从句子 *I like to train networks* 中得到以下配对：(like,I)、(I, like)、(to, like)、(like,to)、(train,to)、(to, train)、(networks, train)、(train,networks)。这里，第一个单词是作为输入的邻近词，第二个单词是我们要预测的目标词。\n",
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"\n",
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"为了构建一个预测下一个单词的网络，我们需要将邻近词作为输入，并输出单词编号。CBoW 网络的架构如下：\n",
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"\n",
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"* 输入单词会通过嵌入层处理。这个嵌入层就是我们的 Word2Vec 嵌入，因此我们会将其单独定义为 `embedder` 变量。在这个例子中，我们将使用嵌入维度为 30，尽管你可能希望尝试更高的维度（真实的 Word2Vec 通常使用 300）。\n",
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"* 嵌入向量接着会传递到一个线性层，该层用于预测输出单词。因此它包含 `vocab_size` 个神经元。\n",
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"\n",
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"对于输出，如果我们使用 `CrossEntropyLoss` 作为损失函数，那么我们只需要提供单词编号作为期望结果，而不需要进行独热编码。\n"
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]
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},
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{
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"cell_type": "code",
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"source": [
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"vocab_size = len(vocab)\n",
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"\n",
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"embedder = torch.nn.Embedding(num_embeddings = vocab_size, embedding_dim = 30)\n",
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"model = torch.nn.Sequential(\n",
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" embedder,\n",
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" torch.nn.Linear(in_features = 30, out_features = vocab_size),\n",
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")\n",
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"\n",
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"print(model)"
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],
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"metadata": {
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"colab": {
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"base_uri": "https://localhost:8080/"
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},
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"id": "akKTcKQKkfl2",
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"outputId": "da687e3e-a8ec-4c1a-e456-ab8cd6ac7dad"
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},
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"execution_count": null,
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"Sequential(\n",
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" (0): Embedding(5002, 30)\n",
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" (1): Linear(in_features=30, out_features=5002, bias=True)\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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{
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"cell_type": "markdown",
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"metadata": {
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"id": "Nud6jgGPaHVa"
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},
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"source": [
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"## 准备训练数据\n",
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"\n",
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"现在让我们编写一个主函数，用于从文本中计算CBoW词对。这个函数将允许我们指定窗口大小，并返回一组词对——输入词和输出词。请注意，这个函数既可以用于单词，也可以用于向量/张量——这将使我们能够在传递给`to_cbow`函数之前对文本进行编码。\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": null,
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"metadata": {
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"colab": {
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"base_uri": "https://localhost:8080/"
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},
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"id": "x-dsXygOieXn",
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"outputId": "c2218280-e540-40ba-9546-efe48d0d714f"
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},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"[['like', 'I'], ['to', 'I'], ['I', 'like'], ['to', 'like'], ['train', 'like'], ['I', 'to'], ['like', 'to'], ['train', 'to'], ['networks', 'to'], ['like', 'train'], ['to', 'train'], ['networks', 'train'], ['to', 'networks'], ['train', 'networks']]\n",
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"[[232, 172], [5, 172], [172, 232], [5, 232], [0, 232], [172, 5], [232, 5], [0, 5], [1202, 5], [232, 0], [5, 0], [1202, 0], [5, 1202], [0, 1202]]\n"
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]
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}
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],
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"source": [
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"def to_cbow(sent,window_size=2):\n",
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" res = []\n",
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" for i,x in enumerate(sent):\n",
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" for j in range(max(0,i-window_size),min(i+window_size+1,len(sent))):\n",
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" if i!=j:\n",
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" res.append([sent[j],x])\n",
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" return res\n",
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"\n",
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"print(to_cbow(['I','like','to','train','networks']))\n",
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"print(to_cbow(encode('I like to train networks', vocab)))"
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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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"id": "XVaaDLjaaHVb"
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},
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"source": [
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"让我们准备训练数据集。我们将遍历所有新闻，调用`to_cbow`获取单词对列表，并将这些对添加到`X`和`Y`中。为了节省时间，我们只考虑前1万条新闻——如果你有更多时间等待，并希望获得更好的嵌入，可以轻松去掉这个限制 :)\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": null,
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"metadata": {
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"id": "54b-Gd9TieXo"
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},
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"outputs": [],
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"source": [
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"X = []\n",
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"Y = []\n",
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"for i, x in zip(range(10000), train_dataset):\n",
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" for w1, w2 in to_cbow(encode(x[1], vocab), window_size = 5):\n",
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" X.append(w1)\n",
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" Y.append(w2)\n",
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"\n",
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"X = torch.tensor(X)\n",
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"Y = torch.tensor(Y)"
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]
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},
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{
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"cell_type": "markdown",
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"source": [
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"我们还将把这些数据转换为一个数据集，并创建数据加载器：\n"
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],
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"metadata": {
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"id": "cwWy0PzXWhN5"
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}
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},
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{
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"cell_type": "code",
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"source": [
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"class SimpleIterableDataset(torch.utils.data.IterableDataset):\n",
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" def __init__(self, X, Y):\n",
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" super(SimpleIterableDataset).__init__()\n",
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" self.data = []\n",
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" for i in range(len(X)):\n",
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" self.data.append( (Y[i], X[i]) )\n",
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" random.shuffle(self.data)\n",
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"\n",
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" def __iter__(self):\n",
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" return iter(self.data)"
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],
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"metadata": {
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"id": "mfoAcGPFZU8p"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"id": "e4NQ_-5waHVc"
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},
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"source": [
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"我们还将把这些数据转换为一个数据集，并创建数据加载器：\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": null,
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"metadata": {
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"id": "AbLUcojlieXo"
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},
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"outputs": [],
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"source": [
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"ds = SimpleIterableDataset(X, Y)\n",
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"dl = torch.utils.data.DataLoader(ds, batch_size = 256)"
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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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"id": "pKQr7sXeaHVc"
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},
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"source": [
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"现在让我们进行实际训练。我们将使用`SGD`优化器，并设置较高的学习率。您也可以尝试使用其他优化器，例如`Adam`。我们将从训练10个周期开始——如果您希望获得更低的损失，可以重新运行此单元格。\n"
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]
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},
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{
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"cell_type": "code",
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"source": [
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"def train_epoch(net, dataloader, lr = 0.01, optimizer = None, loss_fn = torch.nn.CrossEntropyLoss(), epochs = None, report_freq = 1):\n",
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" optimizer = optimizer or torch.optim.Adam(net.parameters(), lr = lr)\n",
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" loss_fn = loss_fn.to(device)\n",
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" net.train()\n",
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"\n",
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" for i in range(epochs):\n",
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" total_loss, j = 0, 0, \n",
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" for labels, features in dataloader:\n",
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" optimizer.zero_grad()\n",
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" features, labels = features.to(device), labels.to(device)\n",
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" out = net(features)\n",
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" loss = loss_fn(out, labels)\n",
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" loss.backward()\n",
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" optimizer.step()\n",
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" total_loss += loss\n",
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" j += 1\n",
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" if i % report_freq == 0:\n",
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" print(f\"Epoch: {i+1}: loss={total_loss.item()/j}\")\n",
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"\n",
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" return total_loss.item()/j"
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],
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"metadata": {
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"id": "HeeCYKr_KF1w"
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},
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"execution_count": null,
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"outputs": []
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},
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{
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"cell_type": "code",
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"source": [
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"train_epoch(net = model, dataloader = dl, optimizer = torch.optim.SGD(model.parameters(), lr = 0.1), loss_fn = torch.nn.CrossEntropyLoss(), epochs = 10)"
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],
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"metadata": {
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"colab": {
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"base_uri": "https://localhost:8080/"
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},
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"id": "KVgwGtDHgDlT",
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"outputId": "2447833f-f0e3-4566-c33d-addbfe2f451d"
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},
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"execution_count": null,
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"Epoch: 1: loss=5.664632366860172\n",
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"Epoch: 2: loss=5.632101973960962\n",
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"Epoch: 3: loss=5.610399051405015\n",
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"Epoch: 4: loss=5.594621561080262\n",
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"Epoch: 5: loss=5.582538017415446\n",
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"Epoch: 6: loss=5.572900234519603\n",
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"Epoch: 7: loss=5.564951676341915\n",
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"Epoch: 8: loss=5.558288112064614\n",
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"Epoch: 9: loss=5.552576955031129\n",
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"Epoch: 10: loss=5.547634165194347\n"
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]
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},
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{
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"output_type": "execute_result",
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"data": {
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"text/plain": [
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"5.547634165194347"
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]
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},
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||
"metadata": {},
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"execution_count": 16
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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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"id": "W8u2qXZmaHVd"
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},
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"source": [
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"## 尝试使用 Word2Vec\n",
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"\n",
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"为了使用 Word2Vec，让我们提取与词汇表中所有单词对应的向量：\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": null,
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"metadata": {
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||
"id": "r8TatcXjkU_t"
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},
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"outputs": [],
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"source": [
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"vectors = torch.stack([embedder(torch.tensor(vocab[s])) for s in vocab.itos], 0)"
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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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||
"id": "3OcX21UOaHVd"
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},
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"source": [
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"让我们看看，例如，单词**Paris**是如何编码成一个向量的：\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": null,
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"metadata": {
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"colab": {
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"base_uri": "https://localhost:8080/"
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},
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||
"id": "bz6tAeLzieXp",
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||
"outputId": "5b20850e-4342-45e9-f840-cfac2b4d61d8"
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},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"tensor([-0.0915, 2.1224, -0.0281, -0.6819, 1.1219, 0.6458, -1.3704, -1.3314,\n",
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" -1.1437, 0.4496, 0.2301, -0.3515, -0.8485, 1.0481, 0.4386, -0.8949,\n",
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" 0.5644, 1.0939, -2.5096, 3.2949, -0.2601, -0.8640, 0.1421, -0.0804,\n",
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" -0.5083, -1.0560, 0.9753, -0.5949, -1.6046, 0.5774],\n",
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" grad_fn=<EmbeddingBackward>)\n"
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]
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}
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],
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"source": [
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"paris_vec = embedder(torch.tensor(vocab['paris']))\n",
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"print(paris_vec)"
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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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||
"id": "pHTJlaeYaHVd"
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||
},
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"source": [
|
||
"使用Word2Vec寻找同义词非常有趣。以下函数将返回与给定输入最接近的`n`个单词。为了找到它们，我们计算$|w_i - v|$的范数，其中$v$是与输入单词对应的向量，$w_i$是词汇表中第$i$个单词的编码。然后我们对数组进行排序，并使用`argsort`返回对应的索引，取列表的前`n`个元素，这些元素编码了词汇表中最接近单词的位置。\n"
|
||
]
|
||
},
|
||
{
|
||
"cell_type": "code",
|
||
"execution_count": null,
|
||
"metadata": {
|
||
"colab": {
|
||
"base_uri": "https://localhost:8080/"
|
||
},
|
||
"id": "NlZyi-_olFar",
|
||
"outputId": "b5dbb163-88c4-4d5a-eaf2-6751f700e98c"
|
||
},
|
||
"outputs": [
|
||
{
|
||
"output_type": "execute_result",
|
||
"data": {
|
||
"text/plain": [
|
||
"['microsoft', 'quoted', 'lp', 'rate', 'top']"
|
||
]
|
||
},
|
||
"metadata": {},
|
||
"execution_count": 56
|
||
}
|
||
],
|
||
"source": [
|
||
"def close_words(x, n = 5):\n",
|
||
" vec = embedder(torch.tensor(vocab[x]))\n",
|
||
" top5 = np.linalg.norm(vectors.detach().numpy() - vec.detach().numpy(), axis = 1).argsort()[:n]\n",
|
||
" return [ vocab.itos[x] for x in top5 ]\n",
|
||
"\n",
|
||
"close_words('microsoft')"
|
||
]
|
||
},
|
||
{
|
||
"cell_type": "code",
|
||
"execution_count": null,
|
||
"metadata": {
|
||
"colab": {
|
||
"base_uri": "https://localhost:8080/"
|
||
},
|
||
"id": "-dQq7xeAln0U",
|
||
"outputId": "66f768c3-c248-4bfd-ce4f-c8ffc6d0dd0d"
|
||
},
|
||
"outputs": [
|
||
{
|
||
"output_type": "execute_result",
|
||
"data": {
|
||
"text/plain": [
|
||
"['basketball', 'lot', 'sinai', 'states', 'healthdaynews']"
|
||
]
|
||
},
|
||
"metadata": {},
|
||
"execution_count": 51
|
||
}
|
||
],
|
||
"source": [
|
||
"close_words('basketball')"
|
||
]
|
||
},
|
||
{
|
||
"cell_type": "code",
|
||
"execution_count": null,
|
||
"metadata": {
|
||
"colab": {
|
||
"base_uri": "https://localhost:8080/"
|
||
},
|
||
"id": "fJXqK26b29sa",
|
||
"outputId": "78f0baba-ffd0-485a-dd87-0a12bedfd7fa"
|
||
},
|
||
"outputs": [
|
||
{
|
||
"output_type": "execute_result",
|
||
"data": {
|
||
"text/plain": [
|
||
"['funds', 'travel', 'sydney', 'japan', 'business']"
|
||
]
|
||
},
|
||
"metadata": {},
|
||
"execution_count": 77
|
||
}
|
||
],
|
||
"source": [
|
||
"close_words('funds')"
|
||
]
|
||
},
|
||
{
|
||
"cell_type": "markdown",
|
||
"metadata": {
|
||
"id": "My0VeTDd3Ji8"
|
||
},
|
||
"source": [
|
||
"## 要点\n",
|
||
"\n",
|
||
"通过使用诸如CBoW这样的巧妙技术，我们可以训练Word2Vec模型。你也可以尝试训练skip-gram模型，该模型通过给定中心词来预测邻近词，看看它的表现如何。\n"
|
||
]
|
||
},
|
||
{
|
||
"cell_type": "markdown",
|
||
"metadata": {},
|
||
"source": [
|
||
"\n---\n\n**免责声明**： \n本文档使用AI翻译服务 [Co-op Translator](https://github.com/Azure/co-op-translator) 进行翻译。尽管我们努力确保翻译的准确性，但请注意，自动翻译可能包含错误或不准确之处。应以原始语言的文档作为权威来源。对于关键信息，建议使用专业人工翻译。我们对因使用此翻译而引起的任何误解或误读不承担责任。\n"
|
||
]
|
||
}
|
||
],
|
||
"metadata": {
|
||
"colab": {
|
||
"collapsed_sections": [],
|
||
"name": "CBoW-PyTorch.ipynb",
|
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"provenance": []
|
||
},
|
||
"interpreter": {
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"hash": "16af2a8bbb083ea23e5e41c7f5787656b2ce26968575d8763f2c4b17f9cd711f"
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"display_name": "Python 3.8.12 ('py38')",
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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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"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": "3.8.12"
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|
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"original_hash": "36df28efe3fe40b6fb0a7fa48fe3ea82",
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"translation_date": "2025-08-31T10:36:21+00:00",
|
||
"source_file": "lessons/5-NLP/15-LanguageModeling/CBoW-PyTorch.ipynb",
|
||
"language_code": "zh"
|
||
}
|
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