Conv2d Tensorflow results wrong - accuracy = 0.0000e+00

Question

I am using tensorflow and keras to classify build a classification model. When running the code below it seems that the output does not seem to converge after each epoch, with the loss steadily increasing and the accuracy contantly set to 0.0000e+00. I am new to machine learning and am not too sure why this is happening.

from sklearn.model_selection import train_test_split
from sklearn.preprocessing import LabelEncoder
from tensorflow.keras.models import Sequential
from tensorflow.keras import Sequential
from tensorflow.keras.layers import Dense, Dropout, Activation, Flatten
from tensorflow.keras.layers import Conv2D, MaxPooling2D
import numpy as np

import time
import tensorflow as tf

from google.colab import drive

drive.mount('/content/drive')
import pandas as pd 
data = pd.read_csv("hmnist_28_28_RGB.csv") 
X = data.iloc[:, 0:-1]
y = data.iloc[:, -1]

X = X / 255.0
X = X.values.reshape(-1,28,28,3)
print(X.shape)

model = Sequential()
model.add(Conv2D(256, (3, 3), input_shape=X.shape[1:]))
model.add(Activation('relu'))
model.add(MaxPooling2D(pool_size=(2, 2)))


model.add(Conv2D(256, (3, 3)))
model.add(Activation('relu'))
model.add(MaxPooling2D(pool_size=(2, 2)))

model.add(Flatten())  # this converts our 3D feature maps to 1D feature vectors

model.add(Dense(64))

model.add(Dense(1))
model.add(Activation('sigmoid'))
model.compile(loss='binary_crossentropy',
              optimizer='adam',
              metrics=['accuracy'])

model.fit(X, y, batch_size=32, epochs=10, validation_split=0.3)

Output

(378, 28, 28, 3)
Epoch 1/10
9/9 [==============================] - 4s 429ms/step - loss: -34.6735 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 2/10
9/9 [==============================] - 4s 400ms/step - loss: -1074.2162 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 3/10
9/9 [==============================] - 4s 399ms/step - loss: -7446.1872 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 4/10
9/9 [==============================] - 4s 396ms/step - loss: -30012.9553 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 5/10
9/9 [==============================] - 4s 406ms/step - loss: -89006.4180 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 6/10
9/9 [==============================] - 4s 400ms/step - loss: -221087.9078 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 7/10
9/9 [==============================] - 4s 399ms/step - loss: -480032.9313 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 8/10
9/9 [==============================] - 4s 403ms/step - loss: -956052.3375 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 9/10
9/9 [==============================] - 4s 396ms/step - loss: -1733128.9000 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00
Epoch 10/10
9/9 [==============================] - 4s 401ms/step - loss: -2953626.5750 - accuracy: 0.0000e+00 - val_loss: nan - val_accuracy: 0.0000e+00

Answer 1

You need to make several changes to your model to make it work.

There are 7 different labels in the dataset, so your last layer needs 7 output neurons.

For your last layer you are currently using sigmoid activation. This is not suitable for multi-class classification. Instead you should use the softmax activation.

As loss function you are using loss='binary_crossentropy' . This is only to be used for binary classification. In your case, since your labels consist of integers loss='sparse_categorical_crossentropy' should be used. You can find more information here .

With the following changes to the last lines of your code:

model.add(Dense(7))
model.add(Activation('softmax'))
model.compile(loss='sparse_categorical_crossentropy',
              optimizer='adam',
              metrics=['accuracy'])

model.fit(X, y, batch_size=32, epochs=10, validation_split=0.3)

You'll get this training history:

(10015, 28, 28, 3)
Epoch 1/10
220/220 [==============================] - 89s 403ms/step - loss: 1.0345 - accuracy: 0.6193 - val_loss: 1.7980 - val_accuracy: 0.4353
Epoch 2/10
220/220 [==============================] - 88s 398ms/step - loss: 0.8282 - accuracy: 0.6851 - val_loss: 3.3646 - val_accuracy: 0.0676
Epoch 3/10
220/220 [==============================] - 88s 399ms/step - loss: 0.6944 - accuracy: 0.7502 - val_loss: 2.9686 - val_accuracy: 0.1228
Epoch 4/10
220/220 [==============================] - 87s 395ms/step - loss: 0.6630 - accuracy: 0.7611 - val_loss: 3.3777 - val_accuracy: 0.0646
Epoch 5/10
220/220 [==============================] - 87s 396ms/step - loss: 0.5976 - accuracy: 0.7812 - val_loss: 2.3929 - val_accuracy: 0.2532
Epoch 6/10
220/220 [==============================] - 87s 396ms/step - loss: 0.5577 - accuracy: 0.7935 - val_loss: 2.9879 - val_accuracy: 0.2592
Epoch 7/10
220/220 [==============================] - 88s 398ms/step - loss: 0.7644 - accuracy: 0.7215 - val_loss: 2.5258 - val_accuracy: 0.2852
Epoch 8/10
220/220 [==============================] - 87s 395ms/step - loss: 0.5629 - accuracy: 0.7879 - val_loss: 2.6053 - val_accuracy: 0.3055
Epoch 9/10
220/220 [==============================] - 89s 404ms/step - loss: 0.5380 - accuracy: 0.8008 - val_loss: 2.7401 - val_accuracy: 0.1694
Epoch 10/10
220/220 [==============================] - 92s 419ms/step - loss: 0.5296 - accuracy: 0.8065 - val_loss: 3.7208 - val_accuracy: 0.0529

The model still needs to be optimized to achieve better results, but in general it works.

I was using this file for the training.