CODEWITHSUNDEEP
kerasconv-neural-networkloss-function
Zarrie
Zarrie

Reputation: 333

Loss & val_loss of keras CNN

I have a dataset of about 160k images of 160 classes and I'm trying to classify them using CNN. Training on 120k images for 20 epochs i start with loss ~ 4.9 and val_loss ~ 4.6 which improves to about 3.3 and 3.2 after 20 epochs. I Really tried to read the documentation of Keras and understand what does that mean, but i couldn't, so I'm asking if someone would explain to me in the context of my model what does that mean for my model. I mean what does the loss score represent? What does it say for the model? 

num_classes = 154
batch_size = 64
input_shape = (50,50,3)
epochs = 20

X, y = load_data()

# input image dimensions
img_rows, img_cols = 50, 50

x_train = x_train.astype('float32')
x_test = x_test.astype('float32')
x_train /= 255
x_test /= 255

# convert class vectors to binary class matrices
y_train = keras.utils.to_categorical(y_train, num_classes)
y_test = keras.utils.to_categorical(y_test, num_classes)

model = Sequential()
model.add(Conv2D(64, kernel_size=(5, 5),
                 activation='relu',
                 padding = 'same',
                 input_shape=input_shape))
model.add(Conv2D(128, (3, 3), activation='relu'))
model.add(MaxPooling2D(pool_size=(3, 3)))
model.add(Dropout(0.20))
model.add(Conv2D(128, (3, 3), activation='relu'))
model.add(MaxPooling2D(pool_size=(2, 2)))
model.add(Dropout(0.25))
model.add(Flatten())
model.add(Dense(128, activation='relu'))
model.add(Dropout(0.5))
model.add(Dense(num_classes, activation='softmax'))

model.compile(loss=keras.losses.categorical_crossentropy,
              optimizer=keras.optimizers.Adadelta(),
              metrics=['accuracy'])

Upvotes: -1

Views: 1424

Answers (1)

Akshay Ravindran
Akshay Ravindran

Reputation: 11

I think it will help to watch a few tutorials online on CNN, to begin with. Basically, you want your loss to reduce with the training epochs which is what is observed in your case. Typically we look at how both losses are evolving over the entire training period. Observing how the train and validation loss is changing helps us have an understand whether the model is overfitting or not. You can check This link for a basic explanation to detect overfitting.

Ideally, you would want both your training as well as test loss to reduce with iterations. It is a measure of the error committed by the model in classification (as accuracy increase you expect the loss to reduce)

Upvotes: 1

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