PROBE on Applications for Dynamic Algorithms

1
PROBE on Applications for Dynamic Algorithms

• Organizing Committee
• Guy Blelloch
• Valerie KingDanny Sleator
• Bob TarjanMikkel Thorup
• Students
• Umut Acar (CMU, graduate)Jorge Vittes (CMU,
  undergraduate)Renato Werneck (Princeton,
  graduate)

2
A Brief History of Dynamic Algorithms

• Maintaining sorted lists with O(log n)-time
  updates AVL, 62
• Maintaining convex hulls in poly-logarithmic time
  Overmars, 80
• Maintaining trees with O(log n)-time edge updates
  Sleator and Tarjan, 81
• Graph connectivity in poly-log time Henzinger
  and King, 95
• Kinetic algorithms for geometric problems Guibas
  , 97
• All pairs shortest paths in better than static
  time King, 99
• 100s of papers all together

3
Potential Applications

• Most data in the "Real World" changes over time

• Web pages get added, modified and deleted

• Flights are delayed

• Robots need to deal with moving obstacles

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But

• Most systems process data in batch mode
• and use ad hoc techniques for dynamic changes,
  e.g.
• building a web indices from scratch and keeping a
  few indices that are updated at different rates
• loading static routing tables on a weekly basis
  and using humans to deal with special
  circumstances.

5
Example Train Dispatching

• Results from an industry survey on "Algorithms
  and
• Control Systems for Computer-Aided Train
  Dispatching" Hellstrom , 1998
• "A small disturbance in the traffic propagates
  fast influencing many trains"
• The 1 problem identified in "key problem areas"
  was
• "Most of the published work done so far has been
  on the static properties of models and
  algorithms, leaving dynamic aspects disregarded."

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Goals of the Workshop and PROBE

• To better understand
• current applications of dynamic algorithms
• problem areas in which they might be used
• the state of the art in the design and
  performance of dynamic algorithms, both in theory
  and practice
• and to develop
• new problems for which to find dynamic algorithms
• new techniques and algorithms
• better connections between algorithms community
  and domain experts.

7
Logistics

• Current tentative plan for workshop
• Co-located with SODA (January 04, New Orleans)
• Ongoing research
• Umut Acar (CMU), Mikkel Thorup (ATT), and Renato
  Werneck (Princeton) are working on a common
  experimental testbed for comparing dynamic tree
  algorithms.
• Umut Acar, Jorge Vittes, Guy Blelloch Automatic
  dynamization