ICFP Programming Contest 2009

• Q: Are you going to use the most recent submissions, or the most recent working submissions.
• A: The most recent working submissions, before 13:00:16

• Q: Will the scoreboard be removed? Will the auto tester be available till 13:00?
• The scoreboard and leaderboard will be be removed with 4 hours to go. The auto testing will be disabled a few minutes before 13:00, to allow the server to focus on accepting your last minute entries and source uploads. Anything uploaded before 13:00:16 will be accepted, but do not count on your teampage being updated in the last hour.

• Q: Will satellites always rotate the same direction as you in your test cases?
• A: Yes, except perhaps satellites round the moon.

• Q: We’re having problems with submission of attached trace for scenarios in problem #3. For instance, attached trace for 3001 works ok on our simulator and produces a score. In fact, we get within 55m of the target and stay there for >900 seconds without firing the engine. However, when I submit this trace, I get timed out error instead of a score. Our simulator appears to work correctly, since we have been able to work through other scenarios (except for problem #3). Can you explain why we’re seeing this result?
• A: It is good practice to check where you are is where you think you should be, and compensate for any simulation or rounding issues.
  (This example failed for us on 3 different VMs, on different architectures, and appears to settle into an orbit 4000M away. We realize this is frustrating, we recommend adding compensation code, because it can read live data from our VM-based sensors.)

• Q: My program keeps crashing! Why? It works fine for me.
• A: Here is a trace of the example running:

  ./hohmann replayXXXX.osf
  0xcafebabe 693 1004
  stepto: 0
  0 2 :  < 2 -2427.97 >  < 3 2.96125 >
  stepto: 1
  CRASH on 1

  Table 6 in the document has a configuration port (0×3E80). This is an inital change the input memory, and must be included in deltas in the output file. So typically the first entry in any submission file format will be the writing of port 0×3E80.

WeightedScore = (SUM of Scores for all 1001 to 3004) +
                f(Score for  4001) +
                f(Score for  4002) +
                f(Score for  4003) +
                f(Score for  4004)

f (x) = if x > 200
        then ((x - 200) * 4) / 3
        else 0

• Q: In problems 400x, the specs mention a refuelling station, plus satellites target0 to target11. However, there seem to be only 11 satellites. Is this an error in the specification?
• There are 12 satillites total, including the refueling station. We have corrected this on the document, v1.8.

• Q: What machine are you running your VM on?
• Redhat, Fedora release 10 (Cambridge), x86_64, gcc -O2 -lm

• Q: Our solution model currently produces very large solutions (>1MB). These are valid solutions, as far as we know, but they are rejected by the uploading system with a database error.
• A: Because of resource limitions, we need to have some sort of limit. We will accept .bz2 versions later this afternoon, if this helps. 1M represents > 22,000 burn event ajustments, which should be plenty.

  Resource clarification: We do not accept solutions > 1M, after compression.

• Q: Its possible you have some issue with validation of task solutions. If you check our submissions for scenario 3003 [...] They all marked as “timed out” although our simulator prints valid score at time step around 0×8099. Then we found a different solution with score time equal to 0xB69, and it was accepted.
• A: Make sure you are actually close to the target. Staying at approximately 999 meters may cause rounding differences. It is good practice to check you distance, and compensate.

• Q: As a quick point of clarification, does firing the thrusters during the 900 seconds cause the timer to restart? We have a run of Meet and Greet that appears to stay within a kilometer for well over 2000 timesteps but that fires thrusters frequently but the score remains zero. Should a solution that fires thrusters frequently but that stays within the target distance pass?
• You need to achive a stable orbit close to the target, without firing thrusters for 900s.

• Q: How is the leaderboard score determined?
• The intention was the summation of the scores for each scenario, where the first group of simulations were worth a total of 400, the second 800, the next 1600, and the final group, 3200.
  One team (who will remain nameless) pointed out that doing nothing on any of the problem 4001 to 4004 gives a score of 200 for all of the four problems. (No fuel used, no satellites met). Rather than have everyone run these, we are weighting the leader board.
  The formula is

  WeightedScore = (SUM of Scores for all 1001 to 3004) +
                  f(Score for  4001) +
                  f(Score for  4002) +
                  f(Score for  4003) +
                  f(Score for  4004)
  
  f (x) = if x > 0
          then ((x - 200) * 4) / 3
          else 0

  This restores the original intent, without changing the individual scores of each test. We do not believe it will make a difference to final 10, and makes the leader score board a more accurate metric of performance.
  So the output score for a specific test remains the same; this only effects the Weighted Scores for the leader board, specifically to avoid everyone needing to run pointless simulations, and an 800 point score inflation.