Institute for Personal Robots in Education (IPRE)‏ CSC 170 Computing: Science and Creativity

● Alan Winfield of Bristol Robotics Laboratory ● A Robot tries to save one and then two robots from falling int a hole |_ EARLY ALGORITHMS

WHAT IS AN ALGORITHM? ● An algorithm is any well-defined computational procedure that takes some value or set of values as input and produces some value or set of values as output ● The decimal equivalent of a binary number ● Algorithms can be non computer based ● Cake recipe, instructions to get to from here to there, find a number in a phonebook – Or how back up your contact list on a cell phone ● Algorithms are much older than computers

● Dances, ceremonies, recipes, and building instructions are all conceptually similar to algorithms ● Babylonians defined some fundamental mathematical procedures ~3,600 years ago ● Genes contain algorithms! ● step-by-step processes to transcribe genes and produce proteins ALGORITHMS Photo credit: Daniel Niles

ALGORITHMS YOU MIGHT HAVE USED THIS WEEK Tie your shoe laces Wasn’t easy, was it? Log in to D2L Enter UA Net ID and password, press something Attended CSc 170 Wake up, do your routine, drove, walked or biked nearby ….. Study for a test Is there really any easy way?

ALGORITHMS YOU'VE SEEN IN CSC 170 ● Determine a letter grade if..else ● Interact with the user ask ● Help a player guess a word in fewer tries repeat until loop ● Find if a digit is in a number for loop ● Create a 5 digit number? secretNumber

ALGORITHMS YOU MIGHT HAVE USED THIS WEEK Luhn algorithm Credit card number validation Recommenders You might also be interested in … PageRank Google’s way of measuring “reputation” of web pages EdgeRank Facebook’s method for determining what is highest up on your news feed

FORMS OF CONTROL IN ALGORITHMS Sequencing Application of each step of an algorithm in order (sometimes: find order) Selection Use of Boolean condition to select execution parts Iteration Repetition of part of an algorithm until a condition is met Recursion Repeated application of the same part of algorithm on smaller problems

PROPERTIES OF ALGORITHMS ● Algorithm + Algorithm = Algorithm ● Part of Algorithm = Algorithm ● Several algorithms may solve the same problem, but in differrent time ● Much of Computer Science research involves development of algorithms that solve difficult problems ● And then implementing them in a programming language to do it as quickly as possible ● Believe it or not, it can take seconds or decades

PROVING QUARKS EXIST ● Kenneth G. Wilson, winner of the 1982 Nobel Prize in physics, found he didn’t have adequate computing power to solve his theory numerically, so he wanted easy ways to use large numbers of parallel processors.” ● “He was decades ahead of his time with respect to computing and networks..” ● So Wilson became a pioneer in the field of supercomputing (Cornell) ● UofA CS and BIOr now looking forpatterns in terabytes, or trillions (1,000,000,000,000) of genomic data

ALGORITHM CORRECTNESS ● We don't only want algorithms to be fast and efficient; we also want them to be correct! ● We also have probabalistic and stochastic algorithms that have a randomness or probability to report an answer ● File download time ● Weather predictions ● Potential Friends on Facebook ● Translating text using probabilistic text generation ● Predicting forest fire danger ● Discovering terroristic activities ● Ask the Magic eight ball

How to Express Algorithms… ● A programmer’s spouse tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.” ● The programmer comes home with 12 loaves of bread ● Algorithms need to be expressed in a context-free, unambiguous way for all participants

WAYS TO EXPRESS ALGORITHMS ● Natural Language ● Pseudo Code ● Programming Language ● Snap! Blocks

Let’s write an algorithm in a natural language ● Write an algorithm in English that takes a binary number such as and reports the decimal equivalent = 1x x x x2 0 = = 13 10