Pat White byelipk

Exercises

Is it okay to initialize all the weights to the same value as long as that value is selected randomly using He initialization?

No. All weights should be initialized to different random values and should not have the same initial value. If weights are symmetrical, meaning they have the same value, it makes it almost impossible for backpropagation to converge to a good solution.

Think of it this way: if all the weights are the same, it's like having just one neuron per layer, but much slower.

The technique we use to break this symmetry is to sample weights randomly.

O(1)

This denotes constant time. Running a statement like if (true) {...} is constant time. Another example of constant time is looking up a value in an object, array, or a hash table.

O(log n)

This denotes logrithmic time. Divide and conquer or recursive algorithms have a O(log n) time complexity.

O(n)

What is a CSRF?

This attack works by including malicous code, usually a link, in a website that accesses another site the user is believed to be authenticated with. If that user session is still authenticated, the attacker may execute unauthroized commands.

Most web applications store session data in a cookie. Browsers will automatically send the cookie on every request to a domain, if it can find the cookie for the domain. The catch is that if the request comes from a different domain, the browser will still send along the cookie.

The Transmission Control Protocol (TCP) was designed to be courteous to the different traffic uses on a network. This notion is at the heart of what makes TCP so reliable, even in the face of competing demands for resources on the poorest of networks.

What makes TCP so reliable? Under the hood, TCP implements a concept called the congestion window. The congrstion window is the number of packets the sender can transmit over the wire until it receives an acknowledgment from the receiver. For example, if we set the congestion window to 1, the sender could send 1 packet to the reciever, then it would have to wait to recieve an acknowledgment. Only then could it send a second packet.

The SSL protocol was implement by Netscape back in the day to facilitate commerce over the internet. E-commerce, as it became known as, required encryption to ensure that customer's personal information was kept safe, and the proper authentication and integrity guarentees were in place.

When SSL is used correctly, a third party cannot read or modify any of the actual data sent over the connection.

The TLS protocol is designed to provide three services to all applications running above it:

Encryption
Authentication

	import numpy as np

	def fetch_batch(X, y, epoch, n_batches, batch_index, batch_size):
	"""
	A generic function that returns the next batch of data to train on.

	Parameters
	==========

	:X: The training examples

	from collections import Counter

	def take_n(data, n, test_condition=lambda x: True):
	"""
	Return index position of first N items that match a test condition.

	Parameters
	==========

	:data: An enumerable, such as a list.

	# A utility written in Ruby to download video from M3U8 files.
	#
	# From Wikipedia:
	#
	# An M3U file is a plain text file that specifies the locations of one or more
	# media files. The file is saved with the "m3u" filename extension if the text
	# is encoded in the local system's default non-Unicode encoding (e.g., a
	# Windows codepage), or with the "m3u8" extension if the text is UTF-8 encoded.

	require 'optparse'

	def time_diff(start_time, end_time)
	seconds_diff = (start_time - end_time).to_i.abs

	hours = seconds_diff / 3600
	seconds_diff -= hours * 3600

	minutes = seconds_diff / 60
	seconds_diff -= minutes * 60

	seconds = seconds_diff

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