inception_v3_finetune.py

import math
import numpy as np
from keras.layers import (
    Dense,
    Activation,
    Dropout,
    Flatten,
    AveragePooling2D,
)
from keras.optimizers import Adam
from keras.models import Model
from keras.callbacks import LearningRateScheduler
from keras import backend as K
from keras.utils.generic_utils import get_custom_objects
from keras.applications.inception_v3 import InceptionV3


BATCH_SIZE = 32
VALIDATION_SPLIT = 0.1
N_CLASSES = 16
EPOCHS = 7


def swish(x):
    return K.sigmoid(x) * x


get_custom_objects().update({"swish": Activation(swish)})


# Learning Step Decay by 10e-1 after every 4 epochs
def step_decay(epoch):
    initial_lrate = 0.001
    drop = 0.1
    epochs_drop = 4.0
    lrate = initial_lrate * math.pow(drop, math.floor((epoch) / epochs_drop))
    return lrate


# Calculates Precision Accuracy
def precision(y_true, y_pred):
    """Precision metric.

    Computes the precision, a metric for multi-label classification of
    how many selected items are relevant.
    """
    true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1)))
    predicted_positives = K.sum(K.round(K.clip(y_pred, 0, 1)))
    precision = true_positives / (predicted_positives + K.epsilon())
    return precision


# Calculates Recall Accuracy
def recall(y_true, y_pred):
    """Recall metric.

    Computes the recall, a metric for multi-label classification of
    how many relevant items are selected.
    """
    true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1)))
    possible_positives = K.sum(K.round(K.clip(y_true, 0, 1)))
    recall = true_positives / (possible_positives + K.epsilon())
    return recall


# Calculates F1 score
def f1(y_true, y_pred):
    def precision(y_true, y_pred):
        true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1)))
        predicted_positives = K.sum(K.round(K.clip(y_pred, 0, 1)))
        precision = true_positives / (predicted_positives + K.epsilon())
        return precision

    def recall(y_true, y_pred):
        true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1)))
        possible_positives = K.sum(K.round(K.clip(y_true, 0, 1)))
        recall = true_positives / (possible_positives + K.epsilon())
        return recall

    precision = precision(y_true, y_pred)
    recall = recall(y_true, y_pred)
    return 2 * ((precision * recall) / (precision + recall + K.epsilon()))


# Inecption_V3 model define
def build_inceptionV3(
    img_shape=(416, 416, 3),
    n_classes=16,
    l2_reg=0.0,
    load_pretrained=True,
    freeze_layers_from="base_model",
):
    # Decide if load pretrained weights from imagenet
    if load_pretrained:
        weights = "imagenet"
    else:
        weights = None

    # Get base model
    base_model = InceptionV3(
        include_top=False,
        weights=weights,
        input_tensor=None,
        input_shape=img_shape
    )

    # Add final layers
    x = base_model.output
    x = AveragePooling2D((8, 8), strides=(8, 8), name="avg_pool")(x)
    x = Flatten(name="flatten")(x)
    x = Dense(
              512,
              activation="swish",
              name="dense_1",
              kernel_initializer="he_uniform"
    )(x)
    x = Dropout(0.25)(x)
    predictions = Dense(
        n_classes,
        activation="softmax",
        name="predictions",
        kernel_initializer="he_uniform",
    )(x)

    # This is the model to be trained
    model = Model(inputs=base_model.input, outputs=predictions)

    # Freeze some layers
    if freeze_layers_from is not None:
        if freeze_layers_from == "base_model":
            print("   Freezing base model layers")
            for layer in base_model.layers:
                layer.trainable = False
        else:
            for i, layer in enumerate(model.layers):
                print(i, layer.name)
            print("   Freezing from layer 0 to " + str(freeze_layers_from))
            for layer in model.layers[:freeze_layers_from]:
                layer.trainable = False
            for layer in model.layers[freeze_layers_from:]:
                layer.trainable = True

    # Compiling Model with Adam Optimizer
    adam = Adam(0.0001)
    model.compile(
        loss="categorical_crossentropy",
        optimizer=adam,
        metrics=[precision, recall, f1]
    )
    return model


if __name__ == "__main__":

    # Loading Cropped Images for Training resized to 416x416
    # x_train_crop = np.load('X_train_crop.npy')
    # y_train_crop = np.load('Y_train_crop.npy')
    # y_train_crop = np_utils.to_categorical(y_train, N_CLASSES)

    # Loading Original Images for training resized to 416x416
    # x_train_original = np.load('X_train.npy')
    # y_train_original = np.load('Y_train.npy')
    # x_valid          = np.load('X_valid.npy')
    # y_valid          = np.load('Y_valid.npy')

    # Loading Original Images for Testing resized to 416x416
    x_test = np.load("X_test.npy")
    y_test = np.load("Y_test_categorical.npy")

    # print(x_train.shape, y_train.shape)

    # Learning Rate Schedule
    lrate = LearningRateScheduler(step_decay)

    # Loading Model
    model = build_inceptionV3()

    # Loading Trained weights
    model.load_weights("inception_v3_crops+images.h5")

    # Model Fitting
    # history = model.fit(x_train_original, y_train_original,
    #       batch_size=BATCH_SIZE,
    #       epochs=EPOCHS,
    #       verbose= 1,
    #     # steps_per_epoch=x_train.shape[0]//BATCH_SIZE,
    #     callbacks = [lrate],
    #     validation_data=(x_valid, y_valid)
    #     )

    # Save model weights
    # model.save_weights('inception_v3_crops+images.h5')

    # Calculate score over test data
    score = model.evaluate(x_test, y_test, verbose=1, batch_size=BATCH_SIZE)

    # Prints Precision, Recall, and F-1 score
    print(score)