ops.py

import tensorflow as tf
from tensorflow.python.framework import ops

# Implementation of conv layer with regularization
# Credit - https://github.com/bamos/dcgan-completion.tensorflow/blob/master/ops.py
def conv2d(input_, output_dim, k_h=5, k_w=5, d_h=2, d_w=2, stddev=0.02, name="conv2d"):
    with tf.variable_scope(name):
        weights = tf.get_variable('w', [k_h, k_w, input_.get_shape()[-1], output_dim],
                            initializer=tf.truncated_normal_initializer(stddev=stddev))
        conv = tf.nn.conv2d(input_, weights, strides=[1, d_h, d_w, 1], padding='SAME')
        biases = tf.get_variable('b', [output_dim], initializer=tf.constant_initializer(0.0))
        conv = tf.nn.bias_add(conv, biases)
        reg = tf.nn.l2_loss(weights) + tf.nn.l2_loss(biases)
        return conv, reg


def lrelu(x, leak=0.2, name="lrelu"):
    with tf.variable_scope(name):
        f1 = 0.5 * (1 + leak)
        f2 = 0.5 * (1 - leak)
    return f1 * x + f2 * abs(x)


class batch_norm(object):
    """Code modification of http://stackoverflow.com/a/33950177"""
    def __init__(self, epsilon=1e-5, momentum=0.9, name="batch_norm"):
        with tf.variable_scope(name):
            self.epsilon = epsilon
            self.momentum = momentum

            self.ema = tf.train.ExponentialMovingAverage(decay=self.momentum)
            self.name = name

    def __call__(self, x, train=True):
        shape = x.get_shape().as_list()

        if train:
            with tf.variable_scope(self.name) as scope:
                self.beta = tf.get_variable("beta", [shape[-1]],
                                    initializer=tf.constant_initializer(0.))
                self.gamma = tf.get_variable("gamma", [shape[-1]],
                                    initializer=tf.random_normal_initializer(1., 0.02))

                batch_mean, batch_var = tf.nn.moments(x, [0, 1, 2], name='moments')
                ema_apply_op = self.ema.apply([batch_mean, batch_var])
                self.ema_mean, self.ema_var = self.ema.average(batch_mean), self.ema.average(batch_var)

                with tf.control_dependencies([ema_apply_op]):
                    mean, var = tf.identity(batch_mean), tf.identity(batch_var)
        else:
            mean, var = self.ema_mean, self.ema_var

        normed = tf.nn.batch_norm_with_global_normalization(
                x, mean, var, self.beta, self.gamma, self.epsilon, scale_after_normalization=True)

        return normed


def my_batch_norm(x, n_out, phase_train):
    """
    Batch normalization on convolutional maps.
    Ref.: http://stackoverflow.com/questions/33949786/how-could-i-use-batch-normalization-in-tensorflow
    Args:
        x:           Tensor, 4D BHWD input maps
        n_out:       integer, depth of input maps
        phase_train: boolean tf.Varialbe, true indicates training phase
        scope:       string, variable scope
    Return:
        normed:      batch-normalized maps
    """
    with tf.variable_scope('bn'):
        beta = tf.Variable(tf.constant(0.0, shape=[n_out]),
                                     name='beta', trainable=True)
        gamma = tf.Variable(tf.constant(1.0, shape=[n_out]),
                                      name='gamma', trainable=True)
        batch_mean, batch_var = tf.nn.moments(x, [0,1,2], name='moments')
        ema = tf.train.ExponentialMovingAverage(decay=0.5)

        def mean_var_with_update():
            ema_apply_op = ema.apply([batch_mean, batch_var])
            with tf.control_dependencies([ema_apply_op]):
                return tf.identity(batch_mean), tf.identity(batch_var)

        mean, var = tf.cond(phase_train,
                            mean_var_with_update,
                            lambda: (ema.average(batch_mean), ema.average(batch_var)))
        normed = tf.nn.batch_normalization(x, mean, var, beta, gamma, 1e-3)
    return normed


def dice_coef(y_true_f, y_pred_f):
    EPS = 1e-5
    smooth = 1.
    intersection = tf.reduce_sum(y_true_f * y_pred_f, keep_dims=True) +EPS
    return (2. * intersection + smooth) / (tf.reduce_sum(y_true_f, keep_dims=True) + tf.reduce_sum(y_pred_f, keep_dims=True) + smooth)


def dice_coef_loss(y_true, y_pred):
    return -dice_coef(y_true, y_pred)