Presenting Interactive Contest Problems in the ICPC Scoring Model

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1 Presenting Interactive Contest Problems in the ICPC Scoring Model ICPC Southern California Region Ed Skochinski Jefery Roberts Marc Furon

2 Swamp County Park

3 Escape from Swamp County Park

4 Escape from Swamp County Park

5 Escape from Swamp County Park

6 Escape from Swamp County Park

7 Escape from Swamp County Park

8 Escape from Swamp County Park

9 Escape from Swamp County Park Interactive Problem Input not all known in advance Contestant program moves through the park one step at a time, discovering barbed vines in the way as it goes The contestant program must find the exit within a finite number of moves to be accepted

10 Adding variety to ICPC problems Traditional problems are batch-oriented Read a text input stream Do something Produce a text output stream Judges will tell you if the result is acceptable or not

11 Visual Challenge Experimental problems with visual, nontext, interactive behavior Implementation of the user interaction becomes a major factor Judging has a subjective component The oooooh, wow factor! Are contestants and/or judges skilled in user interface design and evaluation?

12 Java Challenge Program vs. program competition Competition may not be transitive Java API to interact with the environment A defeats B and B defeats C does not imply A defeats C...but the ICPC is a sporting event, after all Expands the nature of the contest Programming Contest becomes Programming and Game Strategy Contest Evaluation is relative to each other, not to the judges' criteria

13 Other possible expansions Binary I/O Southern California has done this in the past to ask certain problems Read a floppy file system Interpret telemetry data Implement fixed-width font OCR Non-deterministic output More than one possible acceptable result Output post-processed by judges to render a decision

14 How about interactive problems? Have contestant program interact with a judge-provided program Several additional problem types become possible

15 Requirements for Interactive Problems Enforce interaction / control access to input Permit adaptive behavior Maintain the ICPC scoring model Provide an objective test for acceptance Language independence

16 Requirements for Interactive Problems Enforce interaction / control access to input Permit adaptive behavior Maintain the ICPC scoring model Provide an objective test for acceptance Language independence Solution: client-server

17 Implementing Named Pipes C/C++ mkfifo server_to_client./a.out < server_to_client server configfile auditfile > server_to_client Java NO public classes, NO aout.java class aout { public static void main() } mkfifo server_to_client java -cp. aout < server_to_client server configfile auditfile > server_to_client Client starts the dialog!

18 Judges' Responses SYNTAX ERROR RUNTIME ERROR Yes, judges still get uncompilable code! Don't use this for protocol errors. automatic judging may mask error, check execution log PRESENTATION ERROR protocol violation

19 Judges' Responses TIME LIMIT EXCEEDED WRONG ANSWER Runaway CPU I/O timeout Transaction budget exceeded bad deduction or claim Use TIME LIMIT EXCEEDED for exceeding the transaction budget ACCEPTED watch for spurious client output before issuing ACCEPTED.

20 What makes a suitable interactive problem? Online algorithms Games Simulations

21 Recommendations Protocol Use pass/fail criteria, not optimality Train the contestants Text-based, terse, easy to parse Before the contest starts & after warmup Give handshaking code examples Identify problems in descriptions Allow access to the production server Equivalent to on-the-job training Don't let server divulge judge's test case Produce an audit (transcript)

22 Past Experience Southern California has asked two such problems in recent contests Escape from Swamp County Park : escape from the maze in time UniClue : deduce the murder circumstances in a simplified version of Clue Problems were challenging, but achievable 10 teams solved the maze, 5 others tried 5 teams solved Clue, 6 others tried

23 Related Work The JAST environment presented at the 2007 CLI Symposium uses similar techniques to implement a Java Challenge style tournament in a language-independent manner

24 Where to get the code (available 30 Apr 2008)

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