ops.py

import math
import numpy as np 
import tensorflow as tf

from tensorflow.python.framework import ops


class batch_norm(object):
    def __init__(self, epsilon=1e-5, momentum = 0.9, name="batch_norm"):
        with tf.variable_scope(name):
            self.epsilon = epsilon
            self.momentum = momentum
            self.name = name

    def __call__(self, x, train=True):
        return tf.contrib.layers.batch_norm(x, decay=self.momentum, updates_collections=None,
                                            epsilon=self.epsilon, scale=True, scope=self.name)


def binary_cross_entropy(preds, targets, name=None):
    """Computes binary cross entropy given `preds`.

    For brevity, let `x = `, `z = targets`.  The logistic loss is

        loss(x, z) = - sum_i (x[i] * log(z[i]) + (1 - x[i]) * log(1 - z[i]))

    Args:
        preds: A `Tensor` of type `float32` or `float64`.
        targets: A `Tensor` of the same type and shape as `preds`.
    """
    eps = 1e-12
    with ops.op_scope([preds, targets], name, "bce_loss") as name:
        preds = ops.convert_to_tensor(preds, name="preds")
        targets = ops.convert_to_tensor(targets, name="targets")
        return tf.reduce_mean(-(targets * tf.log(preds + eps) +
                              (1. - targets) * tf.log(1. - preds + eps)))


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):
        w = 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_, w, strides=[1, d_h, d_w, 1], padding='SAME')

        biases = tf.get_variable('biases', [output_dim],
                                 initializer=tf.constant_initializer(0.0))
        conv = tf.reshape(tf.nn.bias_add(conv, biases), conv.get_shape())

        return conv


def deconv2d(input_, output_shape, k_h=5, k_w=5, d_h=2, d_w=2, stddev=0.02,
             name="deconv2d", with_w=False):
    with tf.variable_scope(name):
        # filter : [height, width, output_channels, in_channels]
        w = tf.get_variable('w', [k_h, k_w, output_shape[-1], input_.get_shape()[-1]],
                            initializer=tf.random_normal_initializer(stddev=stddev))
        
        try:
            deconv = tf.nn.conv2d_transpose(input_, w, output_shape=output_shape,
                                strides=[1, d_h, d_w, 1])

        # Support for verisons of TensorFlow before 0.7.0
        except AttributeError:
            deconv = tf.nn.deconv2d(input_, w, output_shape=output_shape,
                                strides=[1, d_h, d_w, 1])

        biases = tf.get_variable('biases', [output_shape[-1]],
                                 initializer=tf.constant_initializer(0.0))
        deconv = tf.reshape(tf.nn.bias_add(deconv, biases), deconv.get_shape())

        if with_w:
            return deconv, w, biases
        else:
            return deconv
      

def lrelu(x, leak=0.2, name="lrelu"):
    return tf.maximum(x, leak*x)


def linear(input_, output_size, scope=None, stddev=0.02, bias_start=0.0, with_w=False):
    shape = input_.get_shape().as_list()

    with tf.variable_scope(scope or "Linear"):
        matrix = tf.get_variable("Matrix", [shape[1], output_size], tf.float32,
                                 tf.random_normal_initializer(stddev=stddev))
        bias = tf.get_variable("Bias", [output_size],
            initializer=tf.constant_initializer(bias_start))
        if with_w:
            return tf.matmul(input_, matrix) + bias, matrix, bias
        else:
            return tf.matmul(input_, matrix) + bias