1. CS 180 Problem Solving and Object Oriented Programming Fall 2010 Notes for Week 1: August 23-27, 2010 Aditya Mathur Department of Computer Science Purdue University West Lafayette, IN, USA http://www.cs.purdue.edu/homes/apm/courses/CS180Fall2010/

2. About CS 180 2CS 180. Fall 2010. Week 18/25/10

3. Course Web Site and Other Resources Course Web site: http://www.cs.purdue.edu/homes/apm/courses/CS180Fall2010/ 3CS 180. Fall 2010. Week 1 Java Resources: http://download.oracle.com/javase/1.4.2/docs/api/ http://download.oracle.com/javase/tutorial/ 8/25/10

4. Please note…. Classes will begin at 4:30pm and end at 5:20pm. Please try to be in your seat a few minutes before the class begins and leave after the class ends. All students are encouraged to ask questions. You may interrupt the instructor at any time. The instructor is here to help you learn. Make full use of the instructor. Make full use of the instructor’s office hours I want you to succeed in this class and in your major. I will do all I can to help you succeed; this is my primary responsibility as a professor at Purdue. 4CS 180. Fall 2010. Week 18/25/10

5. Assumptions You have little or no expertise in computer programming using Java. You are hard working. You will not sleep during classes, an if you do, you will not snore! You will not use phones during class and turn them off when you enter the class and leave them off until the class is adjourned. You will not disturb others by talking to your neighbors. You will try to participate in the class by asking questions and responding to questions asked by the instructor. You will use iClickers in the class when requested. 5CS 180. Fall 2010. Week 18/25/10

6. Impact of Assumptions Some of you may get bored during the first four weeks of classes, but others may find appealing the slow pace. For those with some Java experience, we recommend participating in the programming competition. Refer to the course web site for details. Please buy an iClicker. You should skip the class if you need to discuss important matters with your friends. But skipping a class is not a good idea! So maybe you might consider rescheduling the important matters with your friend. 6CS 180. Fall 2010. Week 18/25/10

7. Expectations: Academic Honesty Unless specified otherwise, all labs, projects, and exams are to be completed by you without assistance from anyone else other than the course instructor and the graders. Read the Policies page on the course web site. 7CS 180. Fall 2010. Week 18/25/10

8. Expectations: Attendance You will attend all lectures, labs, and recitations. Attendance is not mandatory but highly recommended. If you miss a lecture, lab or recitation then it is your responsibility to (a) learn on your own the material covered (b) find out if there were any announcements that might affect your course grade. 8CS 180. Fall 2010. Week 18/25/10

9. Textbook Title A Gentle Introduction to Concurrent Programming. Authors Barry Wittman, Aditya Mathur, and Tim Korb Edition Draft 3.0, 2010 Avaialble at Boiler CopyMaker, Room 157, Purdue Memorial Union. Additional resource Java Tutorial iClickers You may buy an iClicker from one of several local bookstores. 9CS 180. Fall 2010. Week 18/25/10

10. Grading ComponentWeight (%) Points Exam 1: W 9/29. 8-10pm. EE 129.15 480 Exam 2: Tue 11/09. 8-10pm. EE 192.15 480 Lab exercises [14] 15 540 Project 1 [Individual] 2 64 Project 2 [Individual] 3 96 Project 3 [Individual] 4 128 Project 4 [Team of 2] 6 192 Project 5 [Team of 3] 10 320 Final Exam30 960 TOTAL 100 3260 Relative grading (curved). 10CS 180. Fall 2010. Week 18/25/10

11. Exams You will be allowed to consult one book of your choice during the all exams. 11CS 180. Fall 2010. Week 18/25/10

12. Feedback Weekly feedback: anonymous via iClickers Tell us about the lectures, labs, recitations How are we doing? 12CS 180. Fall 2010. Week 18/25/10 Weekly feedback: open Tell us in an open forum what needs to improve. Constructive criticism of the class is highly appreciated.

13. Week 1: August 23-27, 2010 What is Computer Science? 13CS 180. Fall 2010. Week 18/25/10

14. Computer Science... …is a discipline just as any other discipline like Mechanical Engineering, Electrical Engineering, Biomedical Engineering,… 14CS 180. Fall 2010. Week 18/25/10 …educates and trains students to work as software engineers, information security specialists, systems engineers,…. …deals with software that drives a large number of devices and systems that we use in our day to day lives,… …consists of subfields such as algorithms, artificial intelligence, computational science and engineering, databases, graphics and visualization, information retrieval, information security, machine learning, modeling and simulation, networking, programming languages and compilers, software engineering,…

15. Computer Scientists... …develop software that drives consumer devices such as smart phones, TVs, stereo systems,… 15CS 180. Fall 2010. Week 18/25/10 …develop software systems that control and manage aircrafts, automobiles, health care networks, power grids, intelligent transportation systems,… …develop systems software such as compilers, operating systems, databases, and search engines on which are built a myriad of other user applications,…. …work alongside engineers to develop software that drives devices such as smart phones or more complex systems such as aircrafts,…

16. Week 1: August 23-27, 2010 Readings And Learning Outcomes 16CS 180. Fall 2010. Week 18/25/10

17. Readings and Exercises from the textbook: Week 1 Chapter 1: 1.1, 1.2 Solve: 1.3, 1.4, 1.7, 1.11, 1.14, 1.26 17CS 180. Fall 2010. Week 18/25/10

18. Learning Outcome-1 Through a sequence of well defined steps you will be able to map a problem statement presented in natural language to a computer program written in the Java programming language. 18CS 180. Fall 2010. Week 18/25/10

19. Learning Outcome-2 You will learn the basics of computer programming that will aid you in learning programming languages other than Java. Some of these other languages include C#, Python, and C. 19CS 180. Fall 2010. Week 18/25/10

20. Learning Outcome-3 You will learn the differences between sequential and concurrent solutions to given problem. This will allow you to write concurrent programs that exploit the power of multi-core microprocessors. 20CS 180. Fall 2010. Week 18/25/10

21. Learning Outcome-4 You will learn about Computer Science as a discipline. This will help you decide whether or not Computer Science is for you! 21CS 180. Fall 2010. Week 18/25/10

22. Learning Outcome-5 You will learn how to use DrJava to edit, compile, debug, and execute Java programs. 22CS 180. Fall 2010. Week 18/25/10

23. Learning Outcome-6 You will learn how to program RidgeSoft robots using Java. 23CS 180. Fall 2010. Week 18/25/10

24. Learning Outcome-7 You will learn how to program Android-based smart phones using Java. 24CS 180. Fall 2010. Week 18/25/10

25. Learning Opportunities in CS 180 Lectures: Basic concepts and techniques 25CS 180. Fall 2010. Week 18/25/10 Labs: Practice solving simple problems on the computer; use robots and smart phones Recitations: Practice solving simple problems by hand; lots of discussion and participation; work in small teams Projects: Solve more complex problems; design, implement, test, document.

26. Learning in CS 180: Prerequisite Desire to learn and the ability to work hard. 268/25/10CS 180. Fall 2010. Week 1

27. Learning in CS 180 Practice, practice and practice 27CS 180. Fall 2010. Week 18/25/10 You will write programs that do not compile at first And when they compile they do not run as expected And when they run as expected, you scream Yippee! So do not be discouraged by errors, these are a part of life’s challenges; overcome them! We are here to help you.

28. Week 1: August 23-27, 2010 Problem Solving and OO Programming 28CS 180. Fall 2010. Week 18/25/10

29. What is “problem solving?” “Problem solving” refers to a set of activities performed in order to solve a given problem. This is a generic term and applies to all disciplines, not only to Computer Science. The following sequence of steps for solving a problem was proposed by George Polya in the 1950’s : Understand the problem Devise a plan Execute the plan Review the solution 29CS 180. Fall 2010. Week 18/25/10

30. What is OO programming? OO, or Object Oriented, programming refers to a set of activities that lead to a computer program, written in an object-oriented language, that when executed on a computer will solve a problem. Java is an OO language used in CS 180. Other OO languages include C++, C#, Delphi, Modula, Oberon, Objective C, Simula, Smalltalk, and many more! 30CS 180. Fall 2010. Week 18/25/10

31. What is Problem solving and OO programming? Problem solving and OO programming refers to a set of activities that allow the mapping of a problem to a computer program, written in an object-oriented language, that when executed on a computer will solves the problem. Here is a simplistic summary of activities that aid in solving a problem using OO programming: Understand the problem Design a solution using objects Implement the design as a well documented program in an OO language Test, debug, and correct the program 31CS 180. Fall 2010. Week 18/25/10

32. What is a multi-core microprocessor? A multi-core microprocessor is a microprocessor chip that contains two or more cores. Each core is capable of executing its own sequence of instructions. A dual-core microprocessor contains 2-cores. A quad-core microprocessor contains 4-cores, and so on. 32CS 180. Fall 2010. Week 18/25/10

33. What is a parallel computer? A computer capable of executing two or more programs in parallel is often referred to as a parallel computer. A computer containing a multi-core microprocessor is a parallel computer. A computer containing two or more single-core microprocessors is also a parallel computer. Nearly every desktop and laptop today is a parallel computer containing a multi-core microprocessor. 33CS 180. Fall 2010. Week 18/25/10

34. What is a sequential program? A sequential program is one that is executed by a computer in a strict sequence, one instruction at a time. Thus, every instruction in the program is executed strictly in the specified sequence. 34CS 180. Fall 2010. Week 18/25/10

35. What is a concurrent program? A concurrent program is one that contains instructions that may be executed in parallel, or concurrently, by a parallel computer. A concurrent program written in Java contains two or more threads. Each thread may be executed concurrently on a parallel computer. 35CS 180. Fall 2010. Week 18/25/10

36. Example 1: Problem solving Problem: Find the maximum in a given set of N integers. Step 1: Understand the problem 1. We know what is a set, an integer and what does “maximum” mean. 2.Can N be zero? Can N be negative? We assume that N>0. 3.Suppose the given set is: {4, -5, 29, 4}. N=4. 4.The maximum in this set is 29. 36CS 180. Fall 2010. Week 18/25/10

37. Example 1: Problem solving: Sequential program Find the maximum Pictorial representation of a sequential algorithm: Output: max integer in S Input: Given set Sequential computation 37CS 180. Fall 2010. Week 18/25/10

38. Example 1: Sequential program Step 2: Design a sequential solution 1.Let S denote the given set. 2.Let S.next() denote the next element from the set. S.next() is empty if we have examined all elements of S. 3.Let currentMax=S.next(); 4.Scan each element of S until we have scanned all. The following two steps are performed for each element in S starting from the second. a)Let newElement=S.next(); b)If currentMax<newElement then reset currentMax to newElement; 5.Display currentMax, it is the desired maximum. 38CS 180. Fall 2010. Week 18/25/10

39. Example 1: Sequential program Step 3: Implement the design as a well documented program in an OO language We will write a Java program later in this course. Step 4: Test, debug, and correct the program We will do this after we have written the program. 39CS 180. Fall 2010. Week 18/25/10

40. Example 1: Problem solving: Parallel program Problem: Find the maximum in a given set of N integers. Step 1: Understand the problem 1. We know what is a set, an integer and what does “maximum” mean. 2.Can N be zero? Can N be negative? We assume that N>0. 3.Suppose the given set is: {4, -5, 29, 4}. N=4. 4.The maximum in this set is 29. 5.We can divide S into disjoint sets S1 and S2 such that their union is S. 6.For example, S1={4, -5}, S2={29, 4}. Maximum of S1 is 4 and of S2 is 29. The maximum of these two maximums is 29 which is the desired maximum. 40CS 180. Fall 2010. Week 18/25/10

41. Example 1: Problem solving: Parallel program Split into S1 and S2 such that S=S1 U S2 Pictorial representation of the parallel algorithm: Output: max integer in S Input: Given set Sequential computation Find max of each set using sequential method. Parallel computation Find max of max of each set. Sequential computation 41CS 180. Fall 2010. Week 18/25/10

42. Example 1: Problem solving: Parallel program Step 2a: Design a concurrent solution assuming a dual core machine is to be used for executing this solution. 1.Let S denote the given set. 2.Let S.next() denote the next element from the set. S.next() is empty if we have examined all elements of S. 3.Divide S into sets S1 and S2 such that S=S1 U S2 4.Let maxS1= max(S1) and maxS2=max(S2). 5.Let max be the larger of maxS1 and maxS2 6. max is the desired maximum. 42CS 180. Fall 2010. Week 18/25/10

43. Example 1: Problem solving: Parallel program Step 2b: Design a concurrent solution: max(S) denotes the maximum of integers in set S. 1.Let S.next() denote the next element from the set. S.next() is empty if we have examined all elements of S. 2.Let currentMax=S.next(); 3.Scan each element of S until we have scanned all. The following two steps are performed for each element in S starting from the second. a)Let newElement=S.next(); b)If currentMax<newElement then reset currentMax to newElement; 4. currentMax, is the desired maximum. 43CS 180. Fall 2010. Week 18/25/10

44. Example 1: Problem solving: Parallel program How many threads of computation do you see in our solution? What does each thread do? Will a thread wait? Why and when? 44CS 180. Fall 2010. Week 18/25/10

45. Why parallel program? For faster solution to a problem. Example: search the entire internet for a keyword. For quick response to a request. Example: Customer request for bank balance. 45CS 180. Fall 2010. Week 18/25/10

46. Example 2: Problem Solving Problem: Given real numbers a, b, and c, compute the value of the following expression: 46CS 180. Fall 2010. Week 18/25/10 Step 1: Understand the problem This one is easy! So let us say we have understood the problem!

47. Example 2: Problem Solving: Sequential Solution 47CS 180. Fall 2010. Week 18/25/10 1: Get a, b, and c. 2: Compute x=b*b 3: Compute y=4*a*c 4: Compute z=x-y 5: Compute p= 6: Output p Step 2: Design a sequential solution

48. Example 2: Problem Solving: Parallel Solution Problem: Given real numbers a, b, and c, compute the value of the following expression: 48CS 180. Fall 2010. Week 18/25/10 1: Compute x=b*b 2: Compute y=4*a*c 3: Compute z=x-y 4: Compute p= 5: Output p

49. Example 2: Problem solving: Parallel program Compute sub- expressions Pictorial representation of the parallel algorithm: Output: value of the given expression Input: Given numbers Sequential computation Compute another, dependent, sub-expression Parallel computation Compute the square root Sequential computation 49CS 180. Fall 2010. Week 18/25/10

50. Example 2: Problem solving: Parallel program How many threads of computation do you see in our solution? What does each thread do? Will a thread wait? Why and when? 50CS 180. Fall 2010. Week 18/25/10

51. Discussion What differences do you notice in the two problems? 51CS 180. Fall 2010. Week 18/25/10 What impact would these differences have on a concurrent solution? We solved the problem assuming a dual core computer. Would your solution be different of it were to for a quad-core computer? A concurrent program consists of sequential and concurrent steps. Why? What impact do these steps have on the total time to solve a problem on a multi-core computer?

52. Parallelism in real life: Alice In Wonderland 52CS 180. Fall 2010. Week 18/25/10

53. Two types of parallelism Data parallelism: Distribute data across cores; all cores perform the same computation 53CS 180. Fall 2010. Week 18/25/10 Task Parallelism: Distribute tasks across cores; tasks might act on the same or data.

54. Example 3: Rental car reservation Problem: Develop a program that will allow customers to reserve rental car. 54CS 180. Fall 2010. Week 18/25/10 Question: Should this be a sequential or a concurrent program? Why? In case it is a concurrent program, what form of parallelism do you think it will use?

55. Example 4: Sorting data Problem: Develop a program that will sort a given set of data. 55CS 180. Fall 2010. Week 18/25/10 Question: Should this be a sequential or a concurrent program? Why? In case it is a concurrent program, what form of parallelism do you think it will use?

56. Week 1: August 23-27, 2010 Dissecting a Java program 56CS 180. Fall 2010. Week 18/25/10

57. The edit, compile, execute cycle 57CS 180. Fall 2010. Week 18/25/10 Edit a Java program Compile your program Execute your program Syntax error Run time Error or incorrect output No syntax error Program correct In CS 180 we shall use DrJava for editing, compiling and execution. DrJava is an Integrated Development Environment also known as an IDE. Eclipse, JBuilder, and IntelliJ IDEA are a few other Java IDEs. For programming the RidgeSoft robot we shall use RoboJDE..java file(s).class file(s)

58. Elements of a Sequential Java Program Program to be dissected: Program 1.4 in Chapter 1 pages 12-13. 58CS 180. Fall 2010. Week 18/25/10 Go through this program line by line and understand the meaning of each line.

59. Elements of a Concurrent Java Program Program to be dissected: Program 1.7 in Chapter 1 pages 29-30. 59CS 180. Fall 2010. Week 18/25/10 Go through this program line by line and understand the meaning of each line.

60. Week 1: August 23-27, 2010 Hope you enjoyed this week! 60CS 180. Fall 2010. Week 18/25/10