How to use Algorithm How to use Algorithm Visualizations in Your ClassVisualizations in Your Class

Cliff ShafferVirginia Tech

Susan RodgerDuke University

Tom NapsUniversity of

Wisconsin Oshkosh

Steve EdwardsVirginia Tech

Workshop ScheduleWorkshop ScheduleShaffer: Impediments, AlgoViz,

interactivityNaps: JHAVE, quizzingBreakRodger: JFLAP in the classroomEdwards: AVs in CS2Questions Session/AV Playtime

Get AcquaintedGet AcquaintedWho’s whoHave you used an AV for a class?

Survey Results: InterestSurvey Results: InterestTaken during SIGCSE 2010Warning: Self-selected respondersAre AVs useful?

◦Strongly Agree: 12◦Agree: 17◦Neutral: 1

A (bare) majority indicated that they used some sort of visualization with class

Survey: Impediments to Survey: Impediments to UseUse

Lack of knowledge/time to find good AVs: 13

Time to make good AVs: 2Difficulty integrating in class: 9Lack of time within class constraints:

2Uncertainty about quality outcomes:

1Content not relevant to my classes: 1

Difficulty Integrating in Difficulty Integrating in ClassClassWhy is this so hard?Problems:

◦Compatibility with existing materials◦Class time◦Your effort

Levels of UseLevels of UseLecture aide: Just pick a couple to trySelf-serve tutorial or exercise at homeLab sessionLight quizzing: Self studyHeavy quizzing: collect and send to

instructor (JHAVE, TRAKLA)A section of material: Ex: Hashing

tutorialIntegrated into a full course: JFLAP

Help from/for the Help from/for the CommunityCommunity

http://algoviz.org/◦Build a community of users/developers◦Better disseminate best practices

informationProject Support

◦NSF CCLI grant◦NSF NSDL grant◦Connections to NSDL/Ensemble project

AlgoViz.orgAlgoViz.orgA collection of links to over 500AVsAnnotated bibliography of over 500

papersForums, field reportsOpenAlgoViz

AlgoViz TourAlgoViz Tour

AlgoViz Site TrafficAlgoViz Site TrafficTraffic on AlgoViz Portal

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Portal visit countRegression line

AlgoViz AwardsAlgoViz AwardsCommunity-building exerciseSolicited votes from the public on

a slate of nomineesSix winnersHall of Fame: 6+1Adding more for 2011

◦To be announced at the NSF showcase session on Friday morning

Levels of InteractivityLevels of InteractivityPure animation/slide show

◦Sorting out SortingStep-through

◦Most AVs todayQuizzing

◦JHAVE is step-through + quizzingUser-directed walkthrough

◦TRAKLAExplorationTutorials

My Classroom My Classroom Experiences (1)Experiences (1)My life as an AV researcher is

divorced from my life as an instructor!

Been intending for years to use AVs more in my Data Structures course and my senior Algorithms course

My Classroom My Classroom Experiences (2)Experiences (2)Until recently, only sporadic use

◦Hashing tutorial excepted, since that was driven by a “research” agenda. But that worked well!

This semester, frequent use of AVs in lecture◦Binary Treesome◦TRAKLA: Heaps, BST◦Auckland Huffman Coding◦VT Union/Find

Case Study: VT Hashing Case Study: VT Hashing TutorialTutorialOne week of material on hashingCan replace lecture and textbookDrop in place, a complete unitStudy: in-class study vs. lectureSignificantly better performance

on post test for tutorial group

AV SamplerAV SamplerAnimal Backtracking

(Tutorial/slideshow)Union/Find (lecture aide/step

through)Binary Treesome (interactive)TRAKLA Heaps (Tutorial/interactive)VT Hashing (Tutorial, “test mode”,

exploration)Algorithms in Action: Quicksort