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The effectiveness of
choice of programming
language as a diversity
seeking decision
Meine van der Meulen
Miguel Revilla
16 March 2005
The UVa Online Judge
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Initiative of University of Valladolid
1,500 Problems
Over 50,000 authors
3,385,851 Programs (Monday)
C, C++, Pascal, Java
16 March 2005
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Specifications selected
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3 specifications selected:
 Memory-less
 Two
integer inputs
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3n+1 Problem
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1. input n
2. print n
3. if n=1 then stop
4. if n is odd then n := 3n+1
5. if n is even then n := n/2
6. GOTO 2
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Example:
22 11 34 17 52
26 13 40 20 10
5 16 8 4 2 1
3n+1 Problem (2)
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For any two numbers i and j, you are to
determine the maximum cycle length over all
integers between and including i and j
i,j  1..1,000,000
Output: i, j, and the maximum cycle length
Sample input
1 10
100 200
Sample output:
1 10 20
100 200 125
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Testing of the programs
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2,500 pairs of i and j with i, j  1..50
We only consider first submissions
Time limit on each demand
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We accept small deviations:
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 “The
answer is: “
 Commas, empty lines
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Outputs for analysis
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Identical results grouped in “equivalence
classes”
Score functions generated from equivalence
classes
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Some example failure regions
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Diversity: Eckhardt and Lee
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Score function: (, x)
Probability of choosing a program: P( = )
Difficulty function: (x)
Probability of choosing a demand: P(X = x)
Probability of failure on demand:
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Model applied to diverse pairs
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pfd for a single version:
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pfd for a homogeneous pair
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pfd for a diverse-language pair
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3n+1; First program in C
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3n+1; First program in C++
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Factovisors; First program in C
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Conclusion
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For unreliable programs multiple-language
diversity does not make a difference
For more reliable programs, multiple-language
diversity is as good as or better than
homogeneous diversity
Further research: see whether this can be
observed for other specifications as well
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3n+1; One program in Pascal
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