08_cbow.ipynb

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   "cell_type": "raw",
   "metadata": {},
   "source": [
    "---\n",
    "title: 09 Continuous Bag of Words (CBOW) Text Classifier\n",
    "description: Build a continuous bag of words text classifier.\n",
    "---"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<a href=\"https://colab.research.google.com/drive/1lqS67-mbCspIKzx6y9wn7CuP96utWzP2?usp=sharing\" target=\"_blank\"><img align=\"left\" alt=\"Colab\" title=\"Open in Colab\" src=\"https://colab.research.google.com/assets/colab-badge.svg\"></a>\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "FXO-zuq0o5cU"
   },
   "source": [
    "# Continuous Bag of Words (CBOW) Text Classifier\n",
    "\n",
    "The code below implements a continuous bag of words text classifier.\n",
    "- We tokenize the text, create a vocabulary and encode each piece of text in the dataset\n",
    "- The lookup allows for extracting embeddings for each tokenized input\n",
    "- The embedding vectors are added together\n",
    "- The resulting vector is multiplied with a weight matrix, which is then added a bias vector; this results in scores\n",
    "- The scores are applied a softmax to generate probabilities which are used for the final classification\n",
    "\n",
    "The code used in this notebook was inspired by code from the [official repo](https://github.com/neubig/nn4nlp-code) used in the [CMU Neural Networks for NLP class](http://www.phontron.com/class/nn4nlp2021/schedule.html) by [Graham Neubig](http://www.phontron.com/index.php). \n",
    "\n",
    "![img txt](https://github.com/dair-ai/ML-Notebooks/blob/main/img/cbow.png?raw=true)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "id": "ORP_xNj9o3md"
   },
   "outputs": [],
   "source": [
    "import torch\n",
    "import random\n",
    "import torch.nn as nn"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "id": "NO7P5X0tqr-N"
   },
   "outputs": [],
   "source": [
    "%%capture\n",
    "\n",
    "# download the files\n",
    "!wget https://raw.githubusercontent.com/neubig/nn4nlp-code/master/data/classes/dev.txt\n",
    "!wget https://raw.githubusercontent.com/neubig/nn4nlp-code/master/data/classes/test.txt\n",
    "!wget https://raw.githubusercontent.com/neubig/nn4nlp-code/master/data/classes/train.txt\n",
    "\n",
    "# create the data folders\n",
    "!mkdir data data/classes\n",
    "!cp dev.txt data/classes\n",
    "!cp test.txt data/classes\n",
    "!cp train.txt data/classes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "Wa83HOUIq5EP"
   },
   "source": [
    "## Read and Process Data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "id": "D31E3u_UqwTc"
   },
   "outputs": [],
   "source": [
    "# function to read in data, process each line and split columns by \" ||| \"\n",
    "def read_data(filename):\n",
    "    data = []\n",
    "    with open(filename, 'r') as f:\n",
    "        for line in f:\n",
    "            line = line.lower().strip()\n",
    "            line = line.split(' ||| ')\n",
    "            data.append(line)\n",
    "    return data\n",
    "\n",
    "train_data = read_data('data/classes/train.txt')\n",
    "test_data = read_data('data/classes/test.txt')\n",
    "\n",
    "# creating the word and tag indices\n",
    "word_to_index = {}\n",
    "word_to_index[\"<unk>\"] = len(word_to_index) # add <UNK> to dictionary\n",
    "tag_to_index = {}\n",
    "\n",
    "# create word to index dictionary and tag to index dictionary from data\n",
    "def create_dict(data, check_unk=False):\n",
    "    for line in data:\n",
    "        for word in line[1].split(\" \"):\n",
    "            if check_unk == False:\n",
    "                if word not in word_to_index:\n",
    "                    word_to_index[word] = len(word_to_index)\n",
    "            else:\n",
    "                if word not in word_to_index:\n",
    "                    word_to_index[word] = word_to_index[\"<unk>\"]\n",
    "\n",
    "        if line[0] not in tag_to_index:\n",
    "            tag_to_index[line[0]] = len(tag_to_index)\n",
    "\n",
    "create_dict(train_data)\n",
    "create_dict(test_data, check_unk=True)\n",
    "\n",
    "# create word and tag tensors from data\n",
    "def create_tensor(data):\n",
    "    for line in data:\n",
    "        yield([word_to_index[word] for word in line[1].split(\" \")], tag_to_index[line[0]])\n",
    "\n",
    "train_data = list(create_tensor(train_data))\n",
    "test_data = list(create_tensor(test_data))\n",
    "\n",
    "number_of_words = len(word_to_index)\n",
    "number_of_tags = len(tag_to_index)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "cNsjv5misKIi"
   },
   "source": [
    "## Model"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "id": "7JPQ9OUZrC6z"
   },
   "outputs": [],
   "source": [
    "# cpu or gpu\n",
    "device = \"cuda\" if torch.cuda.is_available() else \"cpu\"\n",
    "\n",
    "# create a simple neural network with embedding layer, bias, and xavier initialization\n",
    "class CBoW(torch.nn.Module):\n",
    "    def __init__(self, nwords, ntags, emb_size):\n",
    "        super(CBoW, self).__init__()\n",
    "\n",
    "        # layers\n",
    "        self.embedding = torch.nn.Embedding(nwords, emb_size)\n",
    "        self.linear = torch.nn.Linear(emb_size, ntags)\n",
    "\n",
    "        # use xavier initialization for weights\n",
    "        nn.init.xavier_uniform_(self.embedding.weight)\n",
    "        nn.init.xavier_uniform_(self.linear.weight)\n",
    "\n",
    "    def forward(self, x):\n",
    "        emb = self.embedding(x) # seq x emb_size\n",
    "        out = torch.sum(emb, dim=0) # emb_size\n",
    "        out = out.view(1, -1) # reshape to (1, emb_size)\n",
    "        out = self.linear(out) # 1 x ntags\n",
    "        return out\n",
    "\n",
    "EMB_SIZE = 64\n",
    "model = CBoW(number_of_words, number_of_tags, EMB_SIZE)\n",
    "criterion = torch.nn.CrossEntropyLoss()\n",
    "optimizer = torch.optim.Adam(model.parameters())\n",
    "type = torch.LongTensor\n",
    "\n",
    "if torch.cuda.is_available():\n",
    "    model.to(device)\n",
    "    type = torch.cuda.LongTensor"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/"
    },
    "id": "aycOgcVssgZI",
    "outputId": "efe7bc92-5699-43d4-b382-54fd24d06134"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "epoch: 1 | train loss/sent: 1.4089 | train accuracy: 0.3826 | test accuracy: 0.4149\n",
      "epoch: 2 | train loss/sent: 0.9089 | train accuracy: 0.6358 | test accuracy: 0.4104\n",
      "epoch: 3 | train loss/sent: 0.5298 | train accuracy: 0.8076 | test accuracy: 0.3837\n",
      "epoch: 4 | train loss/sent: 0.3289 | train accuracy: 0.8864 | test accuracy: 0.3670\n",
      "epoch: 5 | train loss/sent: 0.2179 | train accuracy: 0.9254 | test accuracy: 0.3851\n",
      "epoch: 6 | train loss/sent: 0.1529 | train accuracy: 0.9467 | test accuracy: 0.3774\n",
      "epoch: 7 | train loss/sent: 0.1131 | train accuracy: 0.9594 | test accuracy: 0.3774\n",
      "epoch: 8 | train loss/sent: 0.0835 | train accuracy: 0.9719 | test accuracy: 0.3643\n",
      "epoch: 9 | train loss/sent: 0.0594 | train accuracy: 0.9795 | test accuracy: 0.3566\n",
      "epoch: 10 | train loss/sent: 0.0477 | train accuracy: 0.9837 | test accuracy: 0.3706\n"
     ]
    }
   ],
   "source": [
    "# perform training of the Bow model\n",
    "\n",
    "for epoch in range(10):\n",
    "    # perform training\n",
    "    model.train()\n",
    "    random.shuffle(train_data)\n",
    "    total_loss = 0.0\n",
    "    train_correct = 0\n",
    "    for sentence, tag in train_data:\n",
    "        sentence = torch.tensor(sentence).type(type)\n",
    "        tag = torch.tensor([tag]).type(type)\n",
    "        output = model(sentence)\n",
    "        predicted = torch.argmax(output.data.detach()).item()\n",
    "        \n",
    "        loss = criterion(output, tag)\n",
    "        total_loss += loss.item()\n",
    "\n",
    "        optimizer.zero_grad()\n",
    "        loss.backward()\n",
    "        optimizer.step()\n",
    "\n",
    "        if predicted == tag: train_correct+=1\n",
    "\n",
    "    # perform testing of the model\n",
    "    model.eval()\n",
    "    test_correct = 0\n",
    "    for sentence, tag in test_data:\n",
    "        sentence = torch.tensor(sentence).type(type)\n",
    "        output = model(sentence)\n",
    "        predicted = torch.argmax(output.data.detach()).item()\n",
    "        if predicted == tag: test_correct += 1\n",
    "    \n",
    "    # print model performance results\n",
    "    log = f'epoch: {epoch+1} | ' \\\n",
    "        f'train loss/sent: {total_loss/len(train_data):.4f} | ' \\\n",
    "        f'train accuracy: {train_correct/len(train_data):.4f} | ' \\\n",
    "        f'test accuracy: {test_correct/len(test_data):.4f}'\n",
    "    print(log)"
   ]
  }
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