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1049 řádky
38 KiB
1049 řádky
38 KiB
{
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"cells": [
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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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"from google.colab import drive\n",
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"\n",
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"drive.mount('/content/drive', force_remount=True)\n",
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"\n",
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"# 输入daseCV所在的路径\n",
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"# 'daseCV' 文件夹包括 '.py', 'classifiers' 和'datasets'文件夹\n",
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"# 例如 'CV/assignments/assignment1/daseCV/'\n",
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"FOLDERNAME = None\n",
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"\n",
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"assert FOLDERNAME is not None, \"[!] Enter the foldername.\"\n",
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"\n",
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"%cd drive/My\\ Drive\n",
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"%cp -r $FOLDERNAME ../../\n",
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"%cd ../../\n",
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"%cd daseCV/datasets/\n",
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"!bash get_datasets.sh\n",
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"%cd ../../"
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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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"tags": [
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"pdf-title"
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]
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},
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"source": [
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"# 全连接神经网络\n",
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"\n",
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"在前面的作业中，你在CIFAR-10上实现了一个两层的全连接神经网络。那个实现很简单，但不是很模块化，因为损失和梯度计算在一个函数内。对于一个简单的两层网络来说，还可以人为处理，但是当我们使用更大的模型时，人工处理损失和梯度就变得不切实际了。理想情况下，我们希望使用更加模块化的设计来构建网络，这样我们就可以独立地实现不同类型的层，然后将它们整合到不同架构的模型中。"
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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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"tags": [
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"pdf-ignore"
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]
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},
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"source": [
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"在本练习中，我们将使用更模块化的方法实现全连接网络。对于每一层，我们将实现一个`forward`和一个`backward`的函数。`forward`函数将接收输入、权重和其他参数，并返回一个输出和一个`cache`对象，存储反向传播所需的数据，如下所示：\n",
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"\n",
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"```python\n",
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"def layer_forward(x, w):\n",
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" \"\"\" Receive inputs x and weights w \"\"\"\n",
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" # Do some computations ...\n",
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" z = # ... some intermediate value\n",
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" # Do some more computations ...\n",
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" out = # the output\n",
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" \n",
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" cache = (x, w, z, out) # Values we need to compute gradients\n",
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" \n",
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" return out, cache\n",
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"```\n",
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"\n",
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"反向传播将接收上游的梯度和`cache`对象，并返回相对于输入和权重的梯度：\n",
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"\n",
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"```python\n",
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"def layer_backward(dout, cache):\n",
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" \"\"\"\n",
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" Receive dout (derivative of loss with respect to outputs) and cache,\n",
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" and compute derivative with respect to inputs.\n",
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" \"\"\"\n",
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" # Unpack cache values\n",
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" x, w, z, out = cache\n",
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" \n",
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" # Use values in cache to compute derivatives\n",
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" dx = # Derivative of loss with respect to x\n",
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" dw = # Derivative of loss with respect to w\n",
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" \n",
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" return dx, dw\n",
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"```\n",
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"\n",
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"以这种方式实现了一些层之后，我们能够轻松地将它们组合起来，以构建不同架构的分类器。\n",
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"\n",
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"除了实现任意深度的全连接网络外，我们还将探索不同的优化更新规则，并引入Dropout作为正则化器和Batch/Layer归一化工具来更有效地优化网络。\n",
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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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"execution_count": null,
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"metadata": {
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"tags": [
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"pdf-ignore"
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]
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},
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"outputs": [],
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"source": [
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"# As usual, a bit of setup\n",
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"from __future__ import print_function\n",
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"import time\n",
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"import numpy as np\n",
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"import matplotlib.pyplot as plt\n",
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"from daseCV.classifiers.fc_net import *\n",
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"from daseCV.data_utils import get_CIFAR10_data\n",
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"from daseCV.gradient_check import eval_numerical_gradient, eval_numerical_gradient_array\n",
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"from daseCV.solver import Solver\n",
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"\n",
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"%matplotlib inline\n",
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"plt.rcParams['figure.figsize'] = (10.0, 8.0) # set default size of plots\n",
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"plt.rcParams['image.interpolation'] = 'nearest'\n",
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"plt.rcParams['image.cmap'] = 'gray'\n",
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"\n",
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"# for auto-reloading external modules\n",
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"# see http://stackoverflow.com/questions/1907993/autoreload-of-modules-in-ipython\n",
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"%load_ext autoreload\n",
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"%autoreload 2\n",
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"\n",
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"def rel_error(x, y):\n",
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" \"\"\" returns relative error \"\"\"\n",
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" return np.max(np.abs(x - y) / (np.maximum(1e-8, np.abs(x) + np.abs(y))))"
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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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"tags": [
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"pdf-ignore"
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]
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},
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"outputs": [],
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"source": [
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"# Load the (preprocessed) CIFAR10 data.\n",
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"\n",
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"data = get_CIFAR10_data()\n",
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"for k, v in list(data.items()):\n",
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" print(('%s: ' % k, v.shape))"
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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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"# 仿射层：前向传播\n",
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"打开 `daseCV/layers.py` 并实现 `affine_forward` 函数。\n",
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"\n",
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"当你完成上述函数后，你可以用下面的代码测试你的实现正确与否"
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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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"# Test the affine_forward function\n",
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"\n",
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"num_inputs = 2\n",
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"input_shape = (4, 5, 6)\n",
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"output_dim = 3\n",
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"\n",
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"input_size = num_inputs * np.prod(input_shape)\n",
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"weight_size = output_dim * np.prod(input_shape)\n",
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"\n",
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"x = np.linspace(-0.1, 0.5, num=input_size).reshape(num_inputs, *input_shape)\n",
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"w = np.linspace(-0.2, 0.3, num=weight_size).reshape(np.prod(input_shape), output_dim)\n",
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"b = np.linspace(-0.3, 0.1, num=output_dim)\n",
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"\n",
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"\n",
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"out, _ = affine_forward(x, w, b)\n",
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"correct_out = np.array([[ 1.49834967, 1.70660132, 1.91485297],\n",
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" [ 3.25553199, 3.5141327, 3.77273342]])\n",
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"\n",
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"# Compare your output with ours. The error should be around e-9 or less.\n",
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"print('Testing affine_forward function:')\n",
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"print('difference: ', rel_error(out, correct_out))"
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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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"# 仿射层：反向传播\n",
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"实现 `affine_backwards` 函数，并使用数值梯度检查测试你的实现。"
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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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"# Test the affine_backward function\n",
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"np.random.seed(231)\n",
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"x = np.random.randn(10, 2, 3)\n",
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"w = np.random.randn(6, 5)\n",
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"b = np.random.randn(5)\n",
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"dout = np.random.randn(10, 5)\n",
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"\n",
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"dx_num = eval_numerical_gradient_array(lambda x: affine_forward(x, w, b)[0], x, dout)\n",
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"dw_num = eval_numerical_gradient_array(lambda w: affine_forward(x, w, b)[0], w, dout)\n",
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"db_num = eval_numerical_gradient_array(lambda b: affine_forward(x, w, b)[0], b, dout)\n",
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"\n",
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"_, cache = affine_forward(x, w, b)\n",
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"dx, dw, db = affine_backward(dout, cache)\n",
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"\n",
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"# The error should be around e-10 or less\n",
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"print('Testing affine_backward function:')\n",
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"print('dx error: ', rel_error(dx_num, dx))\n",
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"print('dw error: ', rel_error(dw_num, dw))\n",
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"print('db error: ', rel_error(db_num, db))"
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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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"# ReLU 激活函数：前向传播\n",
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"\n",
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"在`relu_forward`函数中实现ReLU激活函数的前向传播，并使用以下代码测试您的实现:"
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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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"# Test the relu_forward function\n",
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"\n",
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"x = np.linspace(-0.5, 0.5, num=12).reshape(3, 4)\n",
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"\n",
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"out, _ = relu_forward(x)\n",
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"correct_out = np.array([[ 0., 0., 0., 0., ],\n",
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" [ 0., 0., 0.04545455, 0.13636364,],\n",
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" [ 0.22727273, 0.31818182, 0.40909091, 0.5, ]])\n",
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"\n",
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"# Compare your output with ours. The error should be on the order of e-8\n",
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"print('Testing relu_forward function:')\n",
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"print('difference: ', rel_error(out, correct_out))"
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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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"# ReLU 激活函数：反向传播\n",
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"\n",
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"在`relu_back`函数中为ReLU激活函数实现反向传播，并使用数值梯度检查来测试你的实现"
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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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"np.random.seed(231)\n",
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"x = np.random.randn(10, 10)\n",
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"dout = np.random.randn(*x.shape)\n",
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"\n",
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"dx_num = eval_numerical_gradient_array(lambda x: relu_forward(x)[0], x, dout)\n",
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"\n",
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"_, cache = relu_forward(x)\n",
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"dx = relu_backward(dout, cache)\n",
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"\n",
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"# The error should be on the order of e-12\n",
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"print('Testing relu_backward function:')\n",
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"print('dx error: ', rel_error(dx_num, dx))"
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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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"tags": [
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"pdf-inline"
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]
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},
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"source": [
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"## Inline Question 1: \n",
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"\n",
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"作业中只要求你实现ReLU,但是神经网络可以使用很多不同的激活函数,每个都有它的优点和缺点。但是，激活函数的一个常见问题是在反向传播时出现零(或接近零)梯度流。下列哪个激活函数会有这个问题？如果在一维情况下考虑这些函数，什么样的输入将会发生这种现象？\n",
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"1. Sigmoid\n",
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"2. ReLU\n",
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"3. Leaky ReLU\n",
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"\n",
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"## Answer:\n",
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"[FILL THIS IN]\n"
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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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"# “三明治” 层\n",
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"\n",
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"在神经网络中有一些常用的层模式。例如，仿射层后面经常跟一个ReLU层。为了简化这些常见模式，我们在文件`daseCV/layer_utils.py`中定义了几个常用的层\n",
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"\n",
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"请查看 `affine_relu_forward` 和 `affine_relu_backward` 函数, 并且运行下列代码进行数值梯度检查："
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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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"from daseCV.layer_utils import affine_relu_forward, affine_relu_backward\n",
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"np.random.seed(231)\n",
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"x = np.random.randn(2, 3, 4)\n",
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"w = np.random.randn(12, 10)\n",
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"b = np.random.randn(10)\n",
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"dout = np.random.randn(2, 10)\n",
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"\n",
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"out, cache = affine_relu_forward(x, w, b)\n",
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"dx, dw, db = affine_relu_backward(dout, cache)\n",
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"\n",
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"dx_num = eval_numerical_gradient_array(lambda x: affine_relu_forward(x, w, b)[0], x, dout)\n",
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"dw_num = eval_numerical_gradient_array(lambda w: affine_relu_forward(x, w, b)[0], w, dout)\n",
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"db_num = eval_numerical_gradient_array(lambda b: affine_relu_forward(x, w, b)[0], b, dout)\n",
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"\n",
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"# Relative error should be around e-10 or less\n",
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"print('Testing affine_relu_forward and affine_relu_backward:')\n",
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"print('dx error: ', rel_error(dx_num, dx))\n",
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"print('dw error: ', rel_error(dw_num, dw))\n",
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"print('db error: ', rel_error(db_num, db))"
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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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"# 损失层：Softmax and SVM\n",
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"\n",
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"在上次作业中你已经实现了这些损失函数，所以这次作业就不用做了，免费送你了。当然，你仍然应该通过查看`daseCV/layers.py`其中的实现来确保理解它们是如何工作的。\n",
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"\n",
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"你可以通过运行以下程序来确保实现是正确的:"
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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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"np.random.seed(231)\n",
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"num_classes, num_inputs = 10, 50\n",
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"x = 0.001 * np.random.randn(num_inputs, num_classes)\n",
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"y = np.random.randint(num_classes, size=num_inputs)\n",
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"\n",
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"dx_num = eval_numerical_gradient(lambda x: svm_loss(x, y)[0], x, verbose=False)\n",
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"loss, dx = svm_loss(x, y)\n",
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"\n",
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"# Test svm_loss function. Loss should be around 9 and dx error should be around the order of e-9\n",
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"print('Testing svm_loss:')\n",
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"print('loss: ', loss)\n",
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"print('dx error: ', rel_error(dx_num, dx))\n",
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"\n",
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"dx_num = eval_numerical_gradient(lambda x: softmax_loss(x, y)[0], x, verbose=False)\n",
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"loss, dx = softmax_loss(x, y)\n",
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"\n",
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"# Test softmax_loss function. Loss should be close to 2.3 and dx error should be around e-8\n",
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"print('\\nTesting softmax_loss:')\n",
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"print('loss: ', loss)\n",
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"print('dx error: ', rel_error(dx_num, dx))"
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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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"# 两层网络\n",
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"\n",
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"在之前的作业中，你已经实现了一个简单的两层神经网络。现在你已经模块化地实现了一些层，你将使用这些模块重新实现两层网络。\n",
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"\n",
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"打开文件`daseCV/classifiers/fc_net`。并完成`TwoLayerNet`类的实现。这个类将作为这个作业中其他网络的模块，所以请通读它以确保你理解了这个API。\n",
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"你可以运行下面的单元来测试您的实现。\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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"outputs": [],
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"source": [
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"np.random.seed(231)\n",
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"N, D, H, C = 3, 5, 50, 7\n",
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"X = np.random.randn(N, D)\n",
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"y = np.random.randint(C, size=N)\n",
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"\n",
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"std = 1e-3\n",
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"model = TwoLayerNet(input_dim=D, hidden_dim=H, num_classes=C, weight_scale=std)\n",
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"\n",
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"print('Testing initialization ... ')\n",
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"W1_std = abs(model.params['W1'].std() - std)\n",
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"b1 = model.params['b1']\n",
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"W2_std = abs(model.params['W2'].std() - std)\n",
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"b2 = model.params['b2']\n",
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"assert W1_std < std / 10, 'First layer weights do not seem right'\n",
|
|
"assert np.all(b1 == 0), 'First layer biases do not seem right'\n",
|
|
"assert W2_std < std / 10, 'Second layer weights do not seem right'\n",
|
|
"assert np.all(b2 == 0), 'Second layer biases do not seem right'\n",
|
|
"\n",
|
|
"print('Testing test-time forward pass ... ')\n",
|
|
"model.params['W1'] = np.linspace(-0.7, 0.3, num=D*H).reshape(D, H)\n",
|
|
"model.params['b1'] = np.linspace(-0.1, 0.9, num=H)\n",
|
|
"model.params['W2'] = np.linspace(-0.3, 0.4, num=H*C).reshape(H, C)\n",
|
|
"model.params['b2'] = np.linspace(-0.9, 0.1, num=C)\n",
|
|
"X = np.linspace(-5.5, 4.5, num=N*D).reshape(D, N).T\n",
|
|
"scores = model.loss(X)\n",
|
|
"correct_scores = np.asarray(\n",
|
|
" [[11.53165108, 12.2917344, 13.05181771, 13.81190102, 14.57198434, 15.33206765, 16.09215096],\n",
|
|
" [12.05769098, 12.74614105, 13.43459113, 14.1230412, 14.81149128, 15.49994135, 16.18839143],\n",
|
|
" [12.58373087, 13.20054771, 13.81736455, 14.43418138, 15.05099822, 15.66781506, 16.2846319 ]])\n",
|
|
"scores_diff = np.abs(scores - correct_scores).sum()\n",
|
|
"assert scores_diff < 1e-6, 'Problem with test-time forward pass'\n",
|
|
"\n",
|
|
"print('Testing training loss (no regularization)')\n",
|
|
"y = np.asarray([0, 5, 1])\n",
|
|
"loss, grads = model.loss(X, y)\n",
|
|
"correct_loss = 3.4702243556\n",
|
|
"assert abs(loss - correct_loss) < 1e-10, 'Problem with training-time loss'\n",
|
|
"\n",
|
|
"model.reg = 1.0\n",
|
|
"loss, grads = model.loss(X, y)\n",
|
|
"correct_loss = 26.5948426952\n",
|
|
"assert abs(loss - correct_loss) < 1e-10, 'Problem with regularization loss'\n",
|
|
"\n",
|
|
"# Errors should be around e-7 or less\n",
|
|
"for reg in [0.0, 0.7]:\n",
|
|
" print('Running numeric gradient check with reg = ', reg)\n",
|
|
" model.reg = reg\n",
|
|
" loss, grads = model.loss(X, y)\n",
|
|
"\n",
|
|
" for name in sorted(grads):\n",
|
|
" f = lambda _: model.loss(X, y)[0]\n",
|
|
" grad_num = eval_numerical_gradient(f, model.params[name], verbose=False)\n",
|
|
" print('%s relative error: %.2e' % (name, rel_error(grad_num, grads[name])))"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# Solver\n",
|
|
"\n",
|
|
"在之前的作业中，模型的训练逻辑与模型本身是耦合的。在这次作业中，按照更加模块化的设计，我们将模型的训练逻辑划分为单独的类。\n",
|
|
"\n",
|
|
"打开文件`daseCV/solver`，通读一遍以熟悉API。然后使用一个`Sovler`实例来训练一个`TwoLayerNet`，它可以在验证集上达到至少`50%`的精度。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"model = TwoLayerNet()\n",
|
|
"solver = None\n",
|
|
"\n",
|
|
"##############################################################################\n",
|
|
"# TODO: Use a Solver instance to train a TwoLayerNet that achieves at least #\n",
|
|
"# 50% accuracy on the validation set. #\n",
|
|
"##############################################################################\n",
|
|
"# *****START OF YOUR CODE (DO NOT DELETE/MODIFY THIS LINE)*****\n",
|
|
"\n",
|
|
"pass\n",
|
|
"\n",
|
|
"# *****END OF YOUR CODE (DO NOT DELETE/MODIFY THIS LINE)*****\n",
|
|
"##############################################################################\n",
|
|
"# END OF YOUR CODE #\n",
|
|
"##############################################################################"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Run this cell to visualize training loss and train / val accuracy\n",
|
|
"\n",
|
|
"plt.subplot(2, 1, 1)\n",
|
|
"plt.title('Training loss')\n",
|
|
"plt.plot(solver.loss_history, 'o')\n",
|
|
"plt.xlabel('Iteration')\n",
|
|
"\n",
|
|
"plt.subplot(2, 1, 2)\n",
|
|
"plt.title('Accuracy')\n",
|
|
"plt.plot(solver.train_acc_history, '-o', label='train')\n",
|
|
"plt.plot(solver.val_acc_history, '-o', label='val')\n",
|
|
"plt.plot([0.5] * len(solver.val_acc_history), 'k--')\n",
|
|
"plt.xlabel('Epoch')\n",
|
|
"plt.legend(loc='lower right')\n",
|
|
"plt.gcf().set_size_inches(15, 12)\n",
|
|
"plt.show()"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# 多层网络\n",
|
|
"\n",
|
|
"接下来，请实现一个带有任意数量的隐层的全连接网络。\n",
|
|
"\n",
|
|
"阅读`daseCV/classifiers/fc_net.py`中的`FullyConnectedNet`类。\n",
|
|
"\n",
|
|
"实现初始化、前向传播和反向传播的函数，暂时不要考虑实现dropout或batch/layer normalization，我们将在后面添加上去。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## 初始化loss和梯度检查\n",
|
|
"\n",
|
|
"刚开始要做完整性检查，运行以下代码来检查初始loss，并对有正则化和无正则化的网络进行梯度检查。请问初始的loss合理吗?\n",
|
|
"\n",
|
|
"在梯度检查中，你应该期望得到1e-7或更少的errors。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"np.random.seed(231)\n",
|
|
"N, D, H1, H2, C = 2, 15, 20, 30, 10\n",
|
|
"X = np.random.randn(N, D)\n",
|
|
"y = np.random.randint(C, size=(N,))\n",
|
|
"\n",
|
|
"for reg in [0, 3.14]:\n",
|
|
" print('Running check with reg = ', reg)\n",
|
|
" model = FullyConnectedNet([H1, H2], input_dim=D, num_classes=C,\n",
|
|
" reg=reg, weight_scale=5e-2, dtype=np.float64)\n",
|
|
"\n",
|
|
" loss, grads = model.loss(X, y)\n",
|
|
" print('Initial loss: ', loss)\n",
|
|
" \n",
|
|
" # Most of the errors should be on the order of e-7 or smaller. \n",
|
|
" # NOTE: It is fine however to see an error for W2 on the order of e-5\n",
|
|
" # for the check when reg = 0.0\n",
|
|
" for name in sorted(grads):\n",
|
|
" f = lambda _: model.loss(X, y)[0]\n",
|
|
" grad_num = eval_numerical_gradient(f, model.params[name], verbose=False, h=1e-5)\n",
|
|
" print('%s relative error: %.2e' % (name, rel_error(grad_num, grads[name])))"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"实现另一个完整性检查，请确保你可以过拟合50个图像的小数据集。首先，我们将尝试一个三层网络，每个隐藏层有100个单元。在接下来的代码中，调整**learning rate**和**weight initialization scale**以达到过拟合，在20 epoch内达到100%的训练精度。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# TODO: Use a three-layer Net to overfit 50 training examples by \n",
|
|
"# tweaking just the learning rate and initialization scale.\n",
|
|
"\n",
|
|
"num_train = 50\n",
|
|
"small_data = {\n",
|
|
" 'X_train': data['X_train'][:num_train],\n",
|
|
" 'y_train': data['y_train'][:num_train],\n",
|
|
" 'X_val': data['X_val'],\n",
|
|
" 'y_val': data['y_val'],\n",
|
|
"}\n",
|
|
"\n",
|
|
"weight_scale = 1e-2 # Experiment with this!\n",
|
|
"learning_rate = 1e-2 # Experiment with this!\n",
|
|
"model = FullyConnectedNet([100, 100],\n",
|
|
" weight_scale=weight_scale, dtype=np.float64)\n",
|
|
"solver = Solver(model, small_data,\n",
|
|
" print_every=10, num_epochs=20, batch_size=25,\n",
|
|
" update_rule='sgd',\n",
|
|
" optim_config={\n",
|
|
" 'learning_rate': learning_rate,\n",
|
|
" }\n",
|
|
" )\n",
|
|
"solver.train()\n",
|
|
"\n",
|
|
"plt.plot(solver.loss_history, 'o')\n",
|
|
"plt.title('Training loss history')\n",
|
|
"plt.xlabel('Iteration')\n",
|
|
"plt.ylabel('Training loss')\n",
|
|
"plt.show()"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"现在尝试使用一个五层的网络，每层100个单元，对50张图片进行训练。同样，你将调整learning rate和weight initialization scale比例，你应该能够在20个epoch内实现100%的训练精度。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# TODO: Use a five-layer Net to overfit 50 training examples by \n",
|
|
"# tweaking just the learning rate and initialization scale.\n",
|
|
"\n",
|
|
"num_train = 50\n",
|
|
"small_data = {\n",
|
|
" 'X_train': data['X_train'][:num_train],\n",
|
|
" 'y_train': data['y_train'][:num_train],\n",
|
|
" 'X_val': data['X_val'],\n",
|
|
" 'y_val': data['y_val'],\n",
|
|
"}\n",
|
|
"\n",
|
|
"weight_scale = 1e-1 # Experiment with this!\n",
|
|
"learning_rate = 2e-3 # Experiment with this!\n",
|
|
"model = FullyConnectedNet([100, 100, 100, 100],\n",
|
|
" weight_scale=weight_scale, dtype=np.float64)\n",
|
|
"solver = Solver(model, small_data,\n",
|
|
" print_every=10, num_epochs=20, batch_size=25,\n",
|
|
" update_rule='sgd',\n",
|
|
" optim_config={\n",
|
|
" 'learning_rate': learning_rate,\n",
|
|
" }\n",
|
|
" )\n",
|
|
"solver.train()\n",
|
|
"\n",
|
|
"plt.plot(solver.loss_history, 'o')\n",
|
|
"plt.title('Training loss history')\n",
|
|
"plt.xlabel('Iteration')\n",
|
|
"plt.ylabel('Training loss')\n",
|
|
"plt.show()"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {
|
|
"tags": [
|
|
"pdf-inline"
|
|
]
|
|
},
|
|
"source": [
|
|
"#### Inline Question 2: \n",
|
|
"你注意到训练三层网和训练五层网难度的区别了吗？根据你的经验，哪个网络对initalization scale更敏感?为什么会这样呢?\n",
|
|
"\n",
|
|
"## Answer:\n",
|
|
"[FILL THIS IN]\n"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# 更新规则\n",
|
|
"\n",
|
|
"到目前为止，我们使用了普通的随机梯度下降法(SGD)作为我们的更新规则。更复杂的更新规则可以更容易地训练深度网络。我们将实现一些最常用的更新规则，并将它们与普通的SGD进行比较。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# SGD+Momentum\n",
|
|
"\n",
|
|
"带动量的随机梯度下降法是一种广泛使用的更新规则，它使深度网络的收敛速度快于普通的随机梯度下降法。更多信息参见http://cs231n.github.io/neural-networks-3/#sgd 动量更新部分。\n",
|
|
"\n",
|
|
"打开文件`daseCV/optim`，并阅读该文件顶部的文档，以确保你理解了该API。在函数`sgd_momentum`中实现SGD+动量更新规则，并运行以下代码检查你的实现。你会看到errors小于e-8。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"from daseCV.optim import sgd_momentum\n",
|
|
"\n",
|
|
"N, D = 4, 5\n",
|
|
"w = np.linspace(-0.4, 0.6, num=N*D).reshape(N, D)\n",
|
|
"dw = np.linspace(-0.6, 0.4, num=N*D).reshape(N, D)\n",
|
|
"v = np.linspace(0.6, 0.9, num=N*D).reshape(N, D)\n",
|
|
"\n",
|
|
"config = {'learning_rate': 1e-3, 'velocity': v}\n",
|
|
"next_w, _ = sgd_momentum(w, dw, config=config)\n",
|
|
"\n",
|
|
"expected_next_w = np.asarray([\n",
|
|
" [ 0.1406, 0.20738947, 0.27417895, 0.34096842, 0.40775789],\n",
|
|
" [ 0.47454737, 0.54133684, 0.60812632, 0.67491579, 0.74170526],\n",
|
|
" [ 0.80849474, 0.87528421, 0.94207368, 1.00886316, 1.07565263],\n",
|
|
" [ 1.14244211, 1.20923158, 1.27602105, 1.34281053, 1.4096 ]])\n",
|
|
"expected_velocity = np.asarray([\n",
|
|
" [ 0.5406, 0.55475789, 0.56891579, 0.58307368, 0.59723158],\n",
|
|
" [ 0.61138947, 0.62554737, 0.63970526, 0.65386316, 0.66802105],\n",
|
|
" [ 0.68217895, 0.69633684, 0.71049474, 0.72465263, 0.73881053],\n",
|
|
" [ 0.75296842, 0.76712632, 0.78128421, 0.79544211, 0.8096 ]])\n",
|
|
"\n",
|
|
"# Should see relative errors around e-8 or less\n",
|
|
"print('next_w error: ', rel_error(next_w, expected_next_w))\n",
|
|
"print('velocity error: ', rel_error(expected_velocity, config['velocity']))"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"当你完成了上面的步骤，运行以下代码来训练一个具有SGD和SGD+momentum的六层网络。你应该看到SGD+momentum更新规则收敛得更快。\n"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"num_train = 4000\n",
|
|
"small_data = {\n",
|
|
" 'X_train': data['X_train'][:num_train],\n",
|
|
" 'y_train': data['y_train'][:num_train],\n",
|
|
" 'X_val': data['X_val'],\n",
|
|
" 'y_val': data['y_val'],\n",
|
|
"}\n",
|
|
"\n",
|
|
"solvers = {}\n",
|
|
"\n",
|
|
"for update_rule in ['sgd', 'sgd_momentum']:\n",
|
|
" print('running with ', update_rule)\n",
|
|
" model = FullyConnectedNet([100, 100, 100, 100, 100], weight_scale=5e-2)\n",
|
|
"\n",
|
|
" solver = Solver(model, small_data,\n",
|
|
" num_epochs=5, batch_size=100,\n",
|
|
" update_rule=update_rule,\n",
|
|
" optim_config={\n",
|
|
" 'learning_rate': 5e-3,\n",
|
|
" },\n",
|
|
" verbose=True)\n",
|
|
" solvers[update_rule] = solver\n",
|
|
" solver.train()\n",
|
|
" print()\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 1)\n",
|
|
"plt.title('Training loss')\n",
|
|
"plt.xlabel('Iteration')\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 2)\n",
|
|
"plt.title('Training accuracy')\n",
|
|
"plt.xlabel('Epoch')\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 3)\n",
|
|
"plt.title('Validation accuracy')\n",
|
|
"plt.xlabel('Epoch')\n",
|
|
"\n",
|
|
"for update_rule, solver in solvers.items():\n",
|
|
" plt.subplot(3, 1, 1)\n",
|
|
" plt.plot(solver.loss_history, 'o', label=\"loss_%s\" % update_rule)\n",
|
|
" \n",
|
|
" plt.subplot(3, 1, 2)\n",
|
|
" plt.plot(solver.train_acc_history, '-o', label=\"train_acc_%s\" % update_rule)\n",
|
|
"\n",
|
|
" plt.subplot(3, 1, 3)\n",
|
|
" plt.plot(solver.val_acc_history, '-o', label=\"val_acc_%s\" % update_rule)\n",
|
|
" \n",
|
|
"for i in [1, 2, 3]:\n",
|
|
" plt.subplot(3, 1, i)\n",
|
|
" plt.legend(loc='upper center', ncol=4)\n",
|
|
"plt.gcf().set_size_inches(15, 15)\n",
|
|
"plt.show()"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# RMSProp and Adam\n",
|
|
"\n",
|
|
"RMSProp [1] 和Adam [2] 是另外两个更新规则，它们通过使用梯度的二阶矩平均值来设置每个参数的学习速率。\n",
|
|
"\n",
|
|
"在文件`daseCV/optim`中实现`RMSProp`函数和`Adam`函数，并使用下面的代码来检查您的实现。\n",
|
|
"\n",
|
|
"[1] Tijmen Tieleman and Geoffrey Hinton. \"Lecture 6.5-rmsprop: Divide the gradient by a running average of its recent magnitude.\" COURSERA: Neural Networks for Machine Learning 4 (2012).\n",
|
|
"\n",
|
|
"[2] Diederik Kingma and Jimmy Ba, \"Adam: A Method for Stochastic Optimization\", ICLR 2015."
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Test RMSProp implementation\n",
|
|
"from daseCV.optim import rmsprop\n",
|
|
"\n",
|
|
"N, D = 4, 5\n",
|
|
"w = np.linspace(-0.4, 0.6, num=N*D).reshape(N, D)\n",
|
|
"dw = np.linspace(-0.6, 0.4, num=N*D).reshape(N, D)\n",
|
|
"cache = np.linspace(0.6, 0.9, num=N*D).reshape(N, D)\n",
|
|
"\n",
|
|
"config = {'learning_rate': 1e-2, 'cache': cache}\n",
|
|
"next_w, _ = rmsprop(w, dw, config=config)\n",
|
|
"\n",
|
|
"expected_next_w = np.asarray([\n",
|
|
" [-0.39223849, -0.34037513, -0.28849239, -0.23659121, -0.18467247],\n",
|
|
" [-0.132737, -0.08078555, -0.02881884, 0.02316247, 0.07515774],\n",
|
|
" [ 0.12716641, 0.17918792, 0.23122175, 0.28326742, 0.33532447],\n",
|
|
" [ 0.38739248, 0.43947102, 0.49155973, 0.54365823, 0.59576619]])\n",
|
|
"expected_cache = np.asarray([\n",
|
|
" [ 0.5976, 0.6126277, 0.6277108, 0.64284931, 0.65804321],\n",
|
|
" [ 0.67329252, 0.68859723, 0.70395734, 0.71937285, 0.73484377],\n",
|
|
" [ 0.75037008, 0.7659518, 0.78158892, 0.79728144, 0.81302936],\n",
|
|
" [ 0.82883269, 0.84469141, 0.86060554, 0.87657507, 0.8926 ]])\n",
|
|
"\n",
|
|
"# You should see relative errors around e-7 or less\n",
|
|
"print('next_w error: ', rel_error(expected_next_w, next_w))\n",
|
|
"print('cache error: ', rel_error(expected_cache, config['cache']))"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Test Adam implementation\n",
|
|
"from daseCV.optim import adam\n",
|
|
"\n",
|
|
"N, D = 4, 5\n",
|
|
"w = np.linspace(-0.4, 0.6, num=N*D).reshape(N, D)\n",
|
|
"dw = np.linspace(-0.6, 0.4, num=N*D).reshape(N, D)\n",
|
|
"m = np.linspace(0.6, 0.9, num=N*D).reshape(N, D)\n",
|
|
"v = np.linspace(0.7, 0.5, num=N*D).reshape(N, D)\n",
|
|
"\n",
|
|
"config = {'learning_rate': 1e-2, 'm': m, 'v': v, 't': 5}\n",
|
|
"next_w, _ = adam(w, dw, config=config)\n",
|
|
"\n",
|
|
"expected_next_w = np.asarray([\n",
|
|
" [-0.40094747, -0.34836187, -0.29577703, -0.24319299, -0.19060977],\n",
|
|
" [-0.1380274, -0.08544591, -0.03286534, 0.01971428, 0.0722929],\n",
|
|
" [ 0.1248705, 0.17744702, 0.23002243, 0.28259667, 0.33516969],\n",
|
|
" [ 0.38774145, 0.44031188, 0.49288093, 0.54544852, 0.59801459]])\n",
|
|
"expected_v = np.asarray([\n",
|
|
" [ 0.69966, 0.68908382, 0.67851319, 0.66794809, 0.65738853,],\n",
|
|
" [ 0.64683452, 0.63628604, 0.6257431, 0.61520571, 0.60467385,],\n",
|
|
" [ 0.59414753, 0.58362676, 0.57311152, 0.56260183, 0.55209767,],\n",
|
|
" [ 0.54159906, 0.53110598, 0.52061845, 0.51013645, 0.49966, ]])\n",
|
|
"expected_m = np.asarray([\n",
|
|
" [ 0.48, 0.49947368, 0.51894737, 0.53842105, 0.55789474],\n",
|
|
" [ 0.57736842, 0.59684211, 0.61631579, 0.63578947, 0.65526316],\n",
|
|
" [ 0.67473684, 0.69421053, 0.71368421, 0.73315789, 0.75263158],\n",
|
|
" [ 0.77210526, 0.79157895, 0.81105263, 0.83052632, 0.85 ]])\n",
|
|
"\n",
|
|
"# You should see relative errors around e-7 or less\n",
|
|
"print('next_w error: ', rel_error(expected_next_w, next_w))\n",
|
|
"print('v error: ', rel_error(expected_v, config['v']))\n",
|
|
"print('m error: ', rel_error(expected_m, config['m']))"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"当你完成了上面RMSProp和Adam函数后，运行下面的代码训练一对网络，其中分别使用了上述两个方法"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"learning_rates = {'rmsprop': 1e-4, 'adam': 1e-3}\n",
|
|
"for update_rule in ['adam', 'rmsprop']:\n",
|
|
" print('running with ', update_rule)\n",
|
|
" model = FullyConnectedNet([100, 100, 100, 100, 100], weight_scale=5e-2)\n",
|
|
"\n",
|
|
" solver = Solver(model, small_data,\n",
|
|
" num_epochs=5, batch_size=100,\n",
|
|
" update_rule=update_rule,\n",
|
|
" optim_config={\n",
|
|
" 'learning_rate': learning_rates[update_rule]\n",
|
|
" },\n",
|
|
" verbose=True)\n",
|
|
" solvers[update_rule] = solver\n",
|
|
" solver.train()\n",
|
|
" print()\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 1)\n",
|
|
"plt.title('Training loss')\n",
|
|
"plt.xlabel('Iteration')\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 2)\n",
|
|
"plt.title('Training accuracy')\n",
|
|
"plt.xlabel('Epoch')\n",
|
|
"\n",
|
|
"plt.subplot(3, 1, 3)\n",
|
|
"plt.title('Validation accuracy')\n",
|
|
"plt.xlabel('Epoch')\n",
|
|
"\n",
|
|
"for update_rule, solver in list(solvers.items()):\n",
|
|
" plt.subplot(3, 1, 1)\n",
|
|
" plt.plot(solver.loss_history, 'o', label=update_rule)\n",
|
|
" \n",
|
|
" plt.subplot(3, 1, 2)\n",
|
|
" plt.plot(solver.train_acc_history, '-o', label=update_rule)\n",
|
|
"\n",
|
|
" plt.subplot(3, 1, 3)\n",
|
|
" plt.plot(solver.val_acc_history, '-o', label=update_rule)\n",
|
|
" \n",
|
|
"for i in [1, 2, 3]:\n",
|
|
" plt.subplot(3, 1, i)\n",
|
|
" plt.legend(loc='upper center', ncol=4)\n",
|
|
"plt.gcf().set_size_inches(15, 15)\n",
|
|
"plt.show()"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {
|
|
"tags": [
|
|
"pdf-inline"
|
|
]
|
|
},
|
|
"source": [
|
|
"## Inline Question 3:\n",
|
|
"\n",
|
|
"AdaGrad，类似于Adam，是一个per-parameter优化方法，它使用以下更新规则:\n",
|
|
"\n",
|
|
"```\n",
|
|
"cache += dw**2\n",
|
|
"w += - learning_rate * dw / (np.sqrt(cache) + eps)\n",
|
|
"```\n",
|
|
"\n",
|
|
"当使用AdaGrad训练一个网络时，更新的值会变得非常小，而且他的网络学习的非常慢。利用你对AdaGrad更新规则的了解，解释为什么更新的值会变得非常小？ Adam会有同样的问题吗？\n",
|
|
"\n",
|
|
"## Answer: \n",
|
|
"[FILL THIS IN]\n"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# 训练一个效果足够好的模型！\n",
|
|
"\n",
|
|
"在CIFAR-10上尽可能训练最好的全连接模型，将最好的模型存储在`best_model`变量中。我们要求你在验证集上获得至少50%的准确性。\n",
|
|
"\n",
|
|
"如果你细心的话，应该是有可能得到55%以上精度的，但我们不苛求你达到这么高的精度。在后面的作业上，我们会要求你们在CIFAR-10上训练最好的卷积神经网络，我们希望你们把精力放在卷积网络上，而不是全连接网络上。\n",
|
|
"\n",
|
|
"在做这部分之前完成`BatchNormalization.ipynb`和`Dropout.ipynb`可能会对你有帮助，因为这些技术可以帮助你训练强大的模型。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"best_model = None\n",
|
|
"################################################################################\n",
|
|
"# TODO: Train the best FullyConnectedNet that you can on CIFAR-10. You might #\n",
|
|
"# find batch/layer normalization and dropout useful. Store your best model in #\n",
|
|
"# the best_model variable. #\n",
|
|
"################################################################################\n",
|
|
"# *****START OF YOUR CODE (DO NOT DELETE/MODIFY THIS LINE)*****\n",
|
|
"\n",
|
|
"pass\n",
|
|
"\n",
|
|
"# *****END OF YOUR CODE (DO NOT DELETE/MODIFY THIS LINE)*****\n",
|
|
"################################################################################\n",
|
|
"# END OF YOUR CODE #\n",
|
|
"################################################################################"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# 测试你的模型！\n",
|
|
"\n",
|
|
"在验证和测试集上运行您的最佳模型。验证集的准确率应达到50%以上。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"y_test_pred = np.argmax(best_model.loss(data['X_test']), axis=1)\n",
|
|
"y_val_pred = np.argmax(best_model.loss(data['X_val']), axis=1)\n",
|
|
"print('Validation set accuracy: ', (y_val_pred == data['y_val']).mean())\n",
|
|
"print('Test set accuracy: ', (y_test_pred == data['y_test']).mean())"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"---\n",
|
|
"# 重要\n",
|
|
"\n",
|
|
"这里是作业的结尾处，请执行以下步骤:\n",
|
|
"\n",
|
|
"1. 点击`File -> Save`或者用`control+s`组合键，确保你最新的的notebook的作业已经保存到谷歌云。\n",
|
|
"2. 执行以下代码确保 `.py` 文件保存回你的谷歌云。"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"import os\n",
|
|
"\n",
|
|
"FOLDER_TO_SAVE = os.path.join('drive/My Drive/', FOLDERNAME)\n",
|
|
"FILES_TO_SAVE = ['daseCV/classifiers/cnn.py', 'daseCV/classifiers/fc_net.py']\n",
|
|
"\n",
|
|
"for files in FILES_TO_SAVE:\n",
|
|
" with open(os.path.join(FOLDER_TO_SAVE, '/'.join(files.split('/')[1:])), 'w') as f:\n",
|
|
" f.write(''.join(open(files).readlines()))"
|
|
]
|
|
}
|
|
],
|
|
"metadata": {
|
|
"kernelspec": {
|
|
"display_name": "Python 3",
|
|
"language": "python",
|
|
"name": "python3"
|
|
},
|
|
"language_info": {
|
|
"codemirror_mode": {
|
|
"name": "ipython",
|
|
"version": 3
|
|
},
|
|
"file_extension": ".py",
|
|
"mimetype": "text/x-python",
|
|
"name": "python",
|
|
"nbconvert_exporter": "python",
|
|
"pygments_lexer": "ipython3",
|
|
"version": "3.7.0"
|
|
}
|
|
},
|
|
"nbformat": 4,
|
|
"nbformat_minor": 4
|
|
}
|