EE422CSoftware Design and Implementation II

Vallath Nandakumar

Fall 2015

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Lecture 1 Announcements

Read syllabus before next classTopics for today

• Introductions• course/syllabus overview• Java

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Websites

Canvas: courses.utexas.eduMy Home Page: ece.users.utexas.edu/~vallathn

Course web-page: accessible from my home pageSlides: will be postedHandouts: Programming Assignments: Subversion repository...

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The teaching team

Instructor• Vallath Nandakumar (

vallathn@austin.utexas.edu)• Office hours: Th 12:30-1:00pm (first week)

• TBD for later weeks• First time teaching this class, and first time in EE• PhD in EECS from UC Berkeley• Several years in Tektronix, AMD in chip design

Graduate TA• Jocelyn Egner (jocelynegner@utexas.edu)• Office hours: TBD

Undergraduate TA• Xavier Salazar (x.salazar1729@utexas.edu)• Office hours: See web page

Contacting the teaching staff

• Post on Piazza if the question might be of general interest.

• Email the instructor or instructors.• Go to office hours.• Emailing through Canvas is not encouraged,

unless it is a response to something the instructor has sent, or a comment that the instructor has made on Canvas.

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Piazza

• Used to make some instructor announcements• Students may ask follow-on questions or make

comments.• Important for students to read these instructor

announcements in a timely manner.• Students may post notes, discussions, or ask

questions.• Students may share allowed assignment-related

material.• May use Piazza to find partner for group

assignments.

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iClicker

• Register your iClicker remote at iClicker.com• Bring your iClicker to every lecture.• Answer at least 3/4 of the questions to get credit

for that day.• If you have questions, email me with your iClicker

remote ID and your UT EID.

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Discussion Section s

• Will be conducted by the TA’s• Might have graded quizzes• Arrive on time, and leave only at the end• Come prepared with questions for TA’s about the

assignments etc.

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EE422C in Context

softwaredesign and

implementationII

(in java)

software engineering

systemssoftware

other nonECE areas

other ECE areas

introductoryprogrammingin C

embedded systems

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goals for this class (1)

how to create appropriate abstractions (e.g., procedural and data) to solve complex programming problems

a practical understanding of a variety of common data structures• when and where they are applicable, and how to

use themknowledge of the advanced constructs of a high level

programming language (java)

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goals for this class (2)

a good understanding of basic software engineering principles and practices• how to analyze a problem?• how to design a system?• how to write good code (conforming to style

standards)?• how to design and test for correctness?• how to analyze program performance?

prepare you to use this knowledge in future courses that require you to develop software/hardware systems

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high points of syllabus

prerequisite, EE312C programming• if no prereq or doesn't seem prereq met, see

meyou are responsible for all materials presented in

classes, whether you attend or not• material presented in class is in addition to the

book.the purpose of the lecture notes is to help you listen

in class ONLYtextbook: data structures and problem solving using

java, 4th edition by mark allen weiss, ISBN 0321541405.

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schedule highlights

• today is our first formal lecture• there will be two in-class exams, and a final exam• programming assignments (6-7) will come out

throughout the semester

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java programming

our first topic of study is java; what’s different from C (or C++)

we will be doing all programming assignments in the java programming language

computer resources available• you can also get a Java compiler and do

assignments at home; but your code must compile/execute on ENS machines

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assignments and grading (1)

assignments will be 6-7 programs • programs to be completed independently

unless i state otherwise• we might do some pair and/or team

programmingTwo in-class exams during the semester

• may have pop quizzes any timegrades made up of:

• 65% exams/quizzes• 35% assignments/exercises, iClicker

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assignments and grading (2)

exam grades may be curved if warrantedassignments turned in late will NOT be acceptedyour program must compile and run successfully on

the ENS lab configuration when graded assignments are normally graded on a 35 point

scale• each assignment may have different criteria• partial credit may be given• correctness, style, performance, etc. will be

scored

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syllabus

all the remaining details of the course policies, rules, grading criteria, and procedures are in the syllabus document on the class blackboard page - read it for next week and be prepared to ask questions

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questions about course administration?

iClicker question

The purpose of iClicker is to:

A.Wake you upB.Make sure you understand just-taught conceptsC.Encourage attendanceD.All of the above

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what is software engineering?

SWE is to CS as ChemE is to chemistrySWEs use a disciplined approach to the

development of software-driven systemsSWE ! = programmer; SE is a relatively new field of

study that applies to all types of systems that are developed as usable products

there are many different jobs that SWEs doit is a challenging career because of the inherent

problems of software - as well as the rate of change in computing technologies, and the ever broadening range of applications

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software is complex

malleableintangibleabstractsolves complex problemsinteracts with other software and hardware

consequently, often software is buggy

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what is a bug?

etymology [wikipedia]• perhaps first use of term in hardware

engineering to describe mechanical failures, e.g.,It has been just so in all of my inventions. The first step is an intuition, and comes with a burst, then difficulties arise—this thing gives out and [it is] then that "Bugs"—as such little faults and difficulties are called—show themselves and months of intense watching, study and labor are requisite before commercial success or failure is certainly reached.

Thomas Edison, 1878

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first actual case of bug being found

harvard mark II

ariane-5, 1996crashed–went off-course 37 sec into flight sequence

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Photos: ESA/CNES

mars polar lander, 1999crashed–premature shut down at 40 meters altitude

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Photos: JPL/NASA

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USS yorktown, 1997“dead in the water” for 3 hours

Photo: navsource.org

What is the Heartbleed bug?

• Exploits a vulnerability in OpenSSL software library, used to implement the Transport Layer Security protocol used in web, instant messaging etc.

• Exposes user’s passwords, cookies and other data to the attacker.

• Not a virus.• One small bug in Open-Source software that

made millions of computers vulnerable.

Buffer over-read bug

The extra data that is sent back is fetched from the server’s memory, due to the bug. It could include passwords and private keys.

Like if someone you had called in to fix your plumbing were to look through your closets for information.

When was this bug introduced discovered, and fixed?Introduced in Dec. 2011, by one of the authors

(Seggelmann) of the (open-source) software team.

Discovered on April 1, by Neel Mehta of Google, and Codenomicon.

Fixed right away, but servers have to use the new software.

khurshid: assertion-driven error recovery 31

warranties–two decades ago

ACM SIGSOFT Software Engineering Notes, Vol. 12, No. 3, July 87

khurshid: assertion-driven error recovery 32

warranties–two decades ago (2)

ACM SIGSOFT Software Engineering Notes, Vol. 12, No. 3, July 87

khurshid: assertion-driven error recovery 33

warranties–today

apple• “Apple warrants the media on which the Apple Software is

recorded and delivered by Apple to be free from defects in materials and

workmanship under normal use for a period of ninety (90) days from the date of original retail purchase.”

• “... THE APPLE SOFTWARE IS PROVIDED "AS IS", WITH ALL FAULTS AND WITHOUT WARRANTY OF ANY KIND ...”

google• “... is provided "as is," with no warranties whatsoever.”

microsoft• “... the Software will perform substantially in accordance with

the accompanying materials for a period of ninety (90) days ...”

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economic impact

“The Economic Impact of Inadequate Infrastructure for Software Testing” NIST Report, May 2002

$59.5B annual cost of inadequate software testing infrastructure

$22.2B annual potential cost reduction from feasible infrastructure improvements

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do you know of any correct program? :-)

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what’s in a name?

anomalybugcrashdefecterror, exceptionfailure, fault, flaw, freezeglitchholeissue...

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correctness

common (partial) properties• segfaults, uncaught exceptions• resource leaks• data races, deadlocks

specific properties• requirements• specification

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traditional waterfall model

requirementsanalysis

designchecking

implementationunit testing

integrationsystem testing

maintenanceverification

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phases (1)

requirements• specify what the software should do• analysis: eliminate/reduce ambiguities,

inconsistencies, and incompletenessdesign

• specify how the software should work• split software into modules, write specifications• checking: check conformance to requirements

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phases (2)

implementation• specify how the modules work• unit testing: test each module in isolation

integration• specify how the modules interact• integration testing: test module interactions• system testing: test entire system

maintenance• evolve software as requirements change• regression testing: test changes

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testing effort

reported to be >50% of development cost [eg. Beizer’90]

microsoft: 75% time spent testing• 50% testers who spend all time testing• 50% developers who spend half time testing

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when to test

the later a bug is found, the higher the cost• orders of magnitude increase in later phases• also the smaller chance of a proper fix

old saying: test often, test earlynew methodology: test-driven development

• write tests before code

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software still buggy

folklore: 1-10 (residual) bugs per 1000 nbnc lines of code (after testing)

consensus: total correctness impossible to achieve for complex software• risk-driven finding/elimination of bugs• focus on specific correctness properties

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approaches for detecting bugs

software testingmodel checking(static) program analysis

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software testing

dynamic approach• run code for some inputs, check outputs

checks correctness for some executionsmain questions

• test-input generation• test-suite adequacy (coverage criteria)• test oracles

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model checking

typically hybrid dynamic/static approachchecks correctness for all executionssome techniques

• explicit-state model checking• symbolic model checking• abstraction-based model checking

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static analysis

static approachchecks correctness for all executionssome techniques

• abstract interpretation• dataflow analysis• verification-condition generation

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current status

testing remains the most widely used approach for bug finding• validation: are we building the right system?• verification: are we building the system right?

a lot of recent progress (say last 7-8 years) on model checking and static analysis• model checking: from hardware to software• static analysis: from sound to practical

vibrant research in the areagap between research and practice

iClicker question

Model-checking and static analysis of programs is hard because of “state-space explosion”. If there is a 1-Mbit memory, the number of states to consider is:

A.1 millionB.2^(1 million)C.Other

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iClicker question

After 1 clock cycle where a memory write can happen, the number of states to explore is:

A.2 millionB.2^(2 million)C.2^(1 million) * 2D.Other

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next time

basics of java and eclipsehands-on experience with small programs

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?/!