Chi / Larissa Face Detection #16 – Tweaking CNN Parameters

Preface

To explore the CNN inner workings a bit more, I want to use this post to tweak some parameters and see how that impacts the filters that were learned by the TFlearn model. Off the top of my naive head, I can think of a few parameters in our CNN that can be optimized:

  • Number of convolutional layers
  • Filter size of convolutional layers
  • Number of filters in each convolutional layer
  • Presence of max pooling layers
  • Size of max pooling
  • Number of nodes in the fully connected layer

Because I’m going to aim to train a few different models, I’m back on AWS so I don’t have to wait 5 minutes per model.

I’ll probably start by tweaking the convolutional layers and go from there.

In [1]:
# Install tflearn
import os
os.system("sudo pip install tflearn")
Out[1]:
0

Feature Building

In [2]:
import numpy as np
import pandas as pd
import copy
from matplotlib import pyplot as plt
%matplotlib inline
In [3]:
# Temporarily load from np arrays
chi_photos_np = np.load('chi_photos_np_0.03_compress.npy')
lars_photos_np = np.load('lars_photos_np_0.03_compress.npy')
In [4]:
# View shape of numpy array
chi_photos_np.shape
Out[4]:
(203, 91, 91)
In [5]:
# Set width var
width = chi_photos_np.shape[-1]
width
Out[5]:
91

Scaling Inputs

In [6]:
# Try out scaler on a manually set data (min of 0, max of 255)
from sklearn.preprocessing import MinMaxScaler
In [7]:
# Set test data list to train on (min of 0, max of 255)
test_list = np.array([0, 255]).reshape(-1, 1)
test_list
Out[7]:
array([[  0],
       [255]])
In [8]:
# Initialize scaler
scaler = MinMaxScaler()
In [9]:
# Fit test list
scaler.fit(test_list)
/usr/lib64/python2.7/dist-packages/sklearn/utils/validation.py:429: DataConversionWarning: Data with input dtype int64 was converted to float64 by MinMaxScaler.
  warnings.warn(msg, _DataConversionWarning)
Out[9]:
MinMaxScaler(copy=True, feature_range=(0, 1))

Reshaping 3D Array To 4D Array

In [10]:
chi_photos_np.reshape(-1, width, width, 1).shape
Out[10]:
(203, 91, 91, 1)

Putting It All Together

In [11]:
# Reshape to prepare for scaler
chi_photos_np_flat = chi_photos_np.reshape(1, -1)
chi_photos_np_flat[:10]
Out[11]:
array([[135, 139, 139, ..., 210, 142, 136]], dtype=uint8)
In [12]:
# Scale
chi_photos_np_scaled = scaler.transform(chi_photos_np_flat)
chi_photos_np_scaled[:10]
Out[12]:
array([[ 0.52941176,  0.54509804,  0.54509804, ...,  0.82352941,
         0.55686275,  0.53333333]])
In [13]:
# Reshape to prepare for scaler
lars_photos_np_flat = lars_photos_np.reshape(1, -1)
lars_photos_np_scaled = scaler.transform(lars_photos_np_flat)
In [14]:
# Reshape
chi_photos_reshaped = chi_photos_np_scaled.reshape(-1, width, width, 1)
lars_photos_reshaped = lars_photos_np_scaled.reshape(-1, width, width, 1)

print('{} has shape: {}'. format('chi_photos_reshaped', chi_photos_reshaped.shape))
print('{} has shape: {}'. format('lars_photos_reshaped', lars_photos_reshaped.shape))
chi_photos_reshaped has shape: (203, 91, 91, 1)
lars_photos_reshaped has shape: (200, 91, 91, 1)
In [15]:
# Create copy of chi's photos to start populating x_input
x_input = copy.deepcopy(chi_photos_reshaped)

print('{} has shape: {}'. format('x_input', x_input.shape))
x_input has shape: (203, 91, 91, 1)
In [16]:
# Concatentate lars' photos to existing x_input
x_input = np.append(x_input, lars_photos_reshaped, axis = 0)

print('{} has shape: {}'. format('x_input', x_input.shape))
x_input has shape: (403, 91, 91, 1)

Preparing Labels

In [17]:
# Create label arrays
y_chi = np.array([[1, 0] for i in chi_photos_reshaped])
y_lars = np.array([[0, 1] for i in lars_photos_reshaped])

print('{} has shape: {}'. format('y_chi', y_chi.shape))
print('{} has shape: {}'. format('y_lars', y_lars.shape))
y_chi has shape: (203, 2)
y_lars has shape: (200, 2)
In [18]:
# Preview the first few elements
y_chi[:5]
Out[18]:
array([[1, 0],
       [1, 0],
       [1, 0],
       [1, 0],
       [1, 0]])
In [19]:
y_lars[:5]
Out[19]:
array([[0, 1],
       [0, 1],
       [0, 1],
       [0, 1],
       [0, 1]])
In [20]:
# Create copy of chi's labels to start populating y_input
y_input = copy.deepcopy(y_chi)

print('{} has shape: {}'. format('y_input', y_input.shape))
y_input has shape: (203, 2)
In [21]:
# Concatentate lars' labels to existing y_input
y_input = np.append(y_input, y_lars, axis = 0)

print('{} has shape: {}'. format('y_input', y_input.shape))
y_input has shape: (403, 2)

CNN #1 – Less Convolutional Filters

I want to try less convolutional filters because looking at 2048 filters on one graph is a bit much haha, a bit hard to tell exactly what’s going on.

If I use 3 filters in each layer of our CNN, I should get a stack of 3 convolutional outputs after conv layer 1, and 9 convolutional outputs after conv layer 2. Hopefully that will be a bit easier on the eyes.

In [22]:
# TFlearn libraries
import tflearn
from tflearn.layers.conv import conv_2d, max_pool_2d
from tflearn.layers.core import input_data, dropout, fully_connected
from tflearn.layers.estimator import regression
In [23]:
# sentdex's code to build the neural net using tflearn
#   Input layer --> conv layer w/ max pooling --> conv layer w/ max pooling --> fully connected layer --> output layer
convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

convnet = conv_2d(convnet, 3, 10, activation = 'relu', name = 'conv_1')
convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

convnet = conv_2d(convnet, 3, 10, activation = 'relu', name = 'conv_2')
convnet = max_pool_2d(convnet, 2, name = 'max_pool_2')

convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
convnet = dropout(convnet, 0.8, name = 'dropout_1')

convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.01, loss = 'categorical_crossentropy', name = 'targets')

Train Test Split

In [24]:
# Import library
from sklearn.model_selection import train_test_split
In [25]:
print(x_input.shape)
print(y_input.shape)
(403, 91, 91, 1)
(403, 2)
In [26]:
# Perform train test split
x_train, x_test, y_train, y_test = train_test_split(x_input, y_input, test_size = 0.1, stratify = y_input)

x_train = np.array(x_train, dtype = np.float64)
x_test = np.array(x_test, dtype = np.float64)
y_train = np.array(y_train, dtype = np.float64)
y_test = np.array(y_test, dtype = np.float64)

Training

In [27]:
# Train with data
model = tflearn.DNN(convnet)
model.fit(
    {'input': x_train},
    {'targets': y_train},
    n_epoch = 10,
    validation_set = ({'input': x_test}, {'targets': y_test}),
    snapshot_step = 500,
    show_metric = True
)
Training Step: 59  | total loss: 0.13480 | time: 0.107s
| SGD | epoch: 010 | loss: 0.13480 - acc: 0.9952 -- iter: 320/362
Training Step: 60  | total loss: 0.12240 | time: 1.133s
| SGD | epoch: 010 | loss: 0.12240 - acc: 0.9958 | val_loss: 0.03329 - val_acc: 1.0000 -- iter: 362/362
--

View Convolutional Filters

In [54]:
import six

def display_convolutions(model, layer, padding=4, filename=''):
    if isinstance(layer, six.string_types):
        vars = tflearn.get_layer_variables_by_name(layer)
        variable = vars[0]
    else:
        variable = layer.W

    data = model.get_weights(variable)

    # N is the total number of convolutions
    N = data.shape[2] * data.shape[3]
    print('There are {} filters in {}'.format(N, layer))

    # Ensure the resulting image is square
    filters_per_row = int(np.ceil(np.sqrt(N)))
    # Assume the filters are square
    filter_size = data.shape[0]
    # Size of the result image including padding
    result_size = filters_per_row * (filter_size + padding) - padding
    # Initialize result image to all zeros
    result = np.zeros((result_size, result_size))

    # Tile the filters into the result image
    filter_x = 0
    filter_y = 0
    for n in range(data.shape[3]):
        for c in range(data.shape[2]):
            if filter_x == filters_per_row:
                filter_y += 1
                filter_x = 0
            for i in range(filter_size):
                for j in range(filter_size):
                    result[filter_y * (filter_size + padding) + i, filter_x * (filter_size + padding) + j] = \
                        data[i, j, c, n]
            filter_x += 1

    # Normalize image to 0-1
    min = result.min()
    max = result.max()
    result = (result - min) / (max - min)

    # Plot figure
    plt.figure(figsize=(10, 10))
    plt.axis('off')
    plt.imshow(result, cmap='gray', interpolation='nearest')

    # Save plot if filename is set
    if filename != '':
        plt.savefig(filename, bbox_inches='tight', pad_inches=0)

    plt.show()
In [29]:
# Display first convolutional layer filters
display_convolutions(model, 'conv_1')
There are 3 filters in conv_1
chi_lars_face_detection_16_1
In [30]:
# Display first convolutional layer filters ( filters)
display_convolutions(model, 'conv_2')
There are 9 filters in conv_2
chi_lars_face_detection_16_2

Hmm… they could potentially represent some part of someone’s face, but it’s still a bit too pixelated to tell… What if I go smaller filter size?

CNN #2 – Smaller Filter Sizes

I used a 10 x 10 filter in each of the layers… let’s go down to a… I dunno, maybe 3 x 3 just for fun?

In [31]:
import tensorflow as tf

with tf.Graph().as_default():
    # Build CNN
    convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

    convnet = conv_2d(convnet, 3, 3, activation = 'relu', name = 'conv_1')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

    convnet = conv_2d(convnet, 3, 3, activation = 'relu', name = 'conv_2')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_2')

    convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
    convnet = dropout(convnet, 0.8, name = 'dropout_1')

    convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
    convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.01, loss = 'categorical_crossentropy', name = 'targets')
       
    # Train Model
    model = tflearn.DNN(convnet)
    model.fit(
        {'input': x_train},
        {'targets': y_train},
        n_epoch = 6,
        validation_set = ({'input': x_test}, {'targets': y_test}),
        snapshot_step = 500,
        show_metric = True
    )
    
    # Display convolutional filters
    display_convolutions(model, 'conv_1')
    display_convolutions(model, 'conv_2')
Training Step: 35  | total loss: 0.42921 | time: 0.096s
| SGD | epoch: 006 | loss: 0.42921 - acc: 0.9963 -- iter: 320/362
Training Step: 36  | total loss: 0.41741 | time: 1.120s
| SGD | epoch: 006 | loss: 0.41741 - acc: 0.9971 | val_loss: 0.33021 - val_acc: 1.0000 -- iter: 362/362
--
There are 3 filters in conv_1
chi_lars_face_detection_16_3
There are 9 filters in conv_2
chi_lars_face_detection_16_4

First of all, I had to import tensorflow and add in

with tf.Graph().as_default():

to somehow separate the new model into another “graph session”. What are these? I’m not sure, but this stack overflow inquiry helped me out a bit. With that, I got my new model training with the same variable names where it was giving me an error earlier.

I trained the model until 6 epochs because that’s when I saw accuracy peak. A manual early stopping mechanism, if you will. Even with 6 epochs and only 3 x 3 filters with 3 filters per convolutional layer, we still reach 99% accuracy!

Again, the filters don’t quite mean anything to me (I’m not sure it can mean anything being 3 pixels by 3 pixels), but I do see some generally brighter colored filters and darker colored filters… perhaps these could represent the face / background and hair respectively!

Let’s try going the other way and making huge filters… why not just cover the entire photo… let’s try it out.

CNN #3 – Larger Filter Sizes

Let’s just use a 91 x 91 filter and see what happens. Maybe this will lend itself to a recognizable filter a bit more.

In [32]:
with tf.Graph().as_default():
    # Build CNN
    convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_1')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_2')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_2')

    convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
    convnet = dropout(convnet, 0.8, name = 'dropout_1')

    convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
    convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.01, loss = 'categorical_crossentropy', name = 'targets')
       
    # Train Model
    model = tflearn.DNN(convnet)
    model.fit(
        {'input': x_train},
        {'targets': y_train},
        n_epoch = 6,
        validation_set = ({'input': x_test}, {'targets': y_test}),
        snapshot_step = 500,
        show_metric = True
    )
    
    # Display convolutional filters
    display_convolutions(model, 'conv_1')
    display_convolutions(model, 'conv_2')
Training Step: 35  | total loss: 0.03914 | time: 0.279s
| SGD | epoch: 006 | loss: 0.03914 - acc: 0.9951 -- iter: 320/362
Training Step: 36  | total loss: 0.03266 | time: 1.344s
| SGD | epoch: 006 | loss: 0.03266 - acc: 0.9961 | val_loss: 0.00603 - val_acc: 1.0000 -- iter: 362/362
--
There are 3 filters in conv_1
chi_lars_face_detection_16_5
There are 9 filters in conv_2
chi_lars_face_detection_16_6

Interesting, it still doesn’t quite make sense to me, but it’s starting to take some type of shape in the second level filters. In that bottom right one in the second layer filters, I can almost even see a face if I squint… Or maybe that’s just my hope and dreams deceiving my eyes right before me. I’m not even sure if we’d be able to really make any sense of the second layer filters because they would be filtering on the activations / outputs of the first layer filter. Only the first layer filter is a filter acting on the original image itself. It’s plausible that one of these may have the silhouette of a person because my filter size is the size of the entire image. There theoretically isn’t even any strides happening here.

Regardless, we would love to see the filters take a smoothed shape as that will indicate the filters have successfully learned some kind of pattern.

Let’s try 3 layers to see what kind of difference that makes.

CNN #4 – More Convolutional Layers

In [43]:
with tf.Graph().as_default():
    # Build CNN
    convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_1')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_2')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_2')
    
    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_3')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_3')

    convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
    convnet = dropout(convnet, 0.8, name = 'dropout_1')

    convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
    convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.01, loss = 'categorical_crossentropy', name = 'targets')
       
    # Train Model
    model = tflearn.DNN(convnet)
    model.fit(
        {'input': x_train},
        {'targets': y_train},
        n_epoch = 10,
        validation_set = ({'input': x_test}, {'targets': y_test}),
        snapshot_step = 500,
        show_metric = True
    )
    
    # Display convolutional filters
    display_convolutions(model, 'conv_1')
    display_convolutions(model, 'conv_2')
    display_convolutions(model, 'conv_3')
Training Step: 59  | total loss: 0.34903 | time: 0.483s
| SGD | epoch: 010 | loss: 0.34903 - acc: 0.9584 -- iter: 320/362
Training Step: 60  | total loss: 0.30831 | time: 1.597s
| SGD | epoch: 010 | loss: 0.30831 - acc: 0.9639 | val_loss: 0.01252 - val_acc: 1.0000 -- iter: 362/362
--
There are 3 filters in conv_1
chi_lars_face_detection_16_7
There are 9 filters in conv_2
chi_lars_face_detection_16_8
There are 9 filters in conv_3
chi_lars_face_detection_16_9

My first thought… how come the third convolution layer only has 9 filters as well? Each output from the second layer (9 outputs) should each be convoluted with the 3 third-layer convolution filter, creating 27 outputs, no? That seems to be what happened between convolutional layers 1 and 2, but I’m not sure why the third filter doesn’t follow this logic… I guess that’s what I get for using a method I’m not too familiar with, on a python package I’m not too familiar with, while viewing the filters through a copied and pasted code I’m not too familiar with.

Baby steps, though, let’s not worry about that too much right now as it looks like it is still giving me the filters (or perhaps at least a subset of the 3rd convolutional layer filters) for each convolutional layer. In fact, I’m going to remove the third layer altogether because it’s way too abstracted for me to understand right now and probably just complicates things.

We are actually starting to see the emergence of some smoother shapes throughout all the filters. The filters are still quite grainy in the grand scheme of things, so maybe I need to train it longer and see if the filters smooth out even more… let’s just go crazy and do 200 epochs. Well, I guess if I were really crazy I’d leave it to train for thousands of epochs overnight, but let’s call 20x more epochs “crazy” for now. Plus, it converges to like 99% accuracy after the 6th epoch anyways.

I also realized that if I’m using a filter size of 91, then the output of my first convolution is probably a single pixel as there is only one unique location that a 91 pixel wide filter can have on a 91 pixel wide image! I’m not even sure how it’s doing the second convolution at this point because how can you convolute a 1 pixel wide image with a 91 pixel wide filter? Hmm let’s just train 1 convolution layer as well.

CNN #5 – More Epochs

In [60]:
with tf.Graph().as_default():
    # Build CNN
    convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

    convnet = conv_2d(convnet, 3, 91, activation = 'relu', name = 'conv_1')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

    convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
    convnet = dropout(convnet, 0.8, name = 'dropout_1')

    convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
    convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.001, loss = 'categorical_crossentropy', name = 'targets')
       
    # Train Model
    model = tflearn.DNN(convnet)
    model.fit(
        {'input': x_train},
        {'targets': y_train},
        n_epoch = 100,
        validation_set = ({'input': x_test}, {'targets': y_test}),
        snapshot_step = 500,
        show_metric = True
    )
    
    # Display convolutional filters
    display_convolutions(model, 'conv_1')
Training Step: 599  | total loss: 0.04104 | time: 0.148s
| SGD | epoch: 100 | loss: 0.04104 - acc: 0.9938 -- iter: 320/362
Training Step: 600  | total loss: 0.03810 | time: 1.182s
| SGD | epoch: 100 | loss: 0.03810 - acc: 0.9944 | val_loss: 0.00898 - val_acc: 1.0000 -- iter: 362/362
--
There are 3 filters in conv_1
chi_lars_face_detection_16_10

At about 0.15s per epoch, plus overhead time, this took us around 3 mins to train. Not too shabby! The top two filters don’t look too smooth to me, but filter on the bottom, call me crazy, kind of has an outline of somebody with long hair. Note quite as crisp as the mock up I drew:

But I do see the general shape! The fact that my 91 x 91 filter theoretically yields an output of 1 pixel really bothers me… I don’t quite want to go back to 10 pixels yet either though, because that really didn’t do much for me. I’m going to try keeping one layer, but more filters of a smaller size.

CNN #6 – More Filters, Smaller Filter Size

In [62]:
with tf.Graph().as_default():
    # Build CNN
    convnet = input_data(shape = [None, 91, 91, 1], name = 'input')

    convnet = conv_2d(convnet, 9, 30, activation = 'relu', name = 'conv_1')
    convnet = max_pool_2d(convnet, 2, name = 'max_pool_1')

    convnet = fully_connected(convnet, 1024, activation = 'relu', name = 'fully_connected_1')
    convnet = dropout(convnet, 0.8, name = 'dropout_1')

    convnet = fully_connected(convnet, 2, activation = 'softmax', name = 'fully_connected_2')
    convnet = regression(convnet, optimizer = 'sgd', learning_rate = 0.001, loss = 'categorical_crossentropy', name = 'targets')
       
    # Train Model
    model = tflearn.DNN(convnet)
    model.fit(
        {'input': x_train},
        {'targets': y_train},
        n_epoch = 100,
        validation_set = ({'input': x_test}, {'targets': y_test}),
        snapshot_step = 500,
        show_metric = True
    )
    
    # Display convolutional filters
    display_convolutions(model, 'conv_1')
Training Step: 599  | total loss: 0.03676 | time: 0.151s
| SGD | epoch: 100 | loss: 0.03676 - acc: 0.9946 -- iter: 320/362
Training Step: 600  | total loss: 0.03411 | time: 1.186s
| SGD | epoch: 100 | loss: 0.03411 - acc: 0.9951 | val_loss: 0.00794 - val_acc: 1.0000 -- iter: 362/362
--
There are 9 filters in conv_1
chi_lars_face_detection_16_11

Not really doing too much here. I think my experiment and test set here is a little too controlled because, with any model, as soon as I get up to 6-7 epochs my validation accuracy goes to 100%. Realistically, the test set is so similar to the training set that there really is no difference other than odd facial expressions here and there.

I think what I need to do perhaps is to actually use the test photos I took in post #13 (me with pants on my head, holding the onion… etc) as my test set and validate on those to get a more natural sense of how the model is doing.

Let’s continue this in our next post.

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