Can you do better?

Challenge Problems

1. (1/17/96)

• Can you find a tour of length 6 days. 7 hours, and 3 minutes for instance tri.3 (start city 0, start time 100).
• Done.

2. (1/17/96)

• Can you find a tour of length under 60 days for instance uk.100 (start city 99, start time 600).
• The bound is now down to about 24 days - how about aiming for 20?
• The lower bound is still trivial on this one (2 days!)

3. (1/17/96)

• Can you find a tour of less than 12 days 6 hours 32 minutes for instance usa.15 (start city 3, start time 0), or can you verify that this is the optimal tour length.
• A 24 second branch and bound program verifies this is optimal -
• Next on the list is usa.20 (18 720).

4. (1/24/96)

• Let's try for a good tour of the biggest instance - uk.284 268 900

5. (1/24/96)

• And for an intermediate instance, let's look at - usa.50 38 60

5. (2/8/96)

• A partial schedule is available for India's Southern Railway. Are these instances easier or more difficulty than the artificial data? Currently there are three data sets.
• south.12 (start city 1, start time 480) It should be possible to solve this one exactly.
• south.18 (start city 2, start time 480) I expect that this one is at the limit of what can be done with branch and bound.
• south.26 (start city 2, start time 480) What is the best you can do on this one - the current bound is two weeks.