UNIVERSITY OF AARHUS DEPARTMENT OF COMPUTER SCIENCE External Memory Algorithms and Data Structures, Fall 1999 

Lecturers · Time and place · Course description · Schedule · Literature · Projects · Evaluation · Prerequisites · Course language · Credits 
In an increasing number of problems, the amount of data to be processed is far too massive to fit into internal memory. Examples include VLSI verification, computer graphics, geographic information systems (GIS), and geological and meteorological databases, where the amount of data may be measured in terabytes.
In such applications, the communication between the fast internal memory and the slow external memory is often the performance bottleneck, and the analysis of algorithms under the assumption of a single level of memory may be meaningless.
Instead, a more realistic measure of the efficiency of an algorithm is the number of I/Ooperations performed between internal memory and disk. Algorithms designed to minimize this number are termed external memory algorithms.
In this course, we will study the design and analysis of efficient external memory algorithms and data structures. Different paradigms for efficiently solving problems in external memory will be covered, and a number of specific algorithms from areas like computational geometry and GIS will be covered.
Date  Topics  Reading 
Sep. 1  Introduction, I/Omodel, Merge sort, Distribution sort  [A97, pp. 18] 
Sep. 3  Btrees  [GT98, pp. 523524, 658664] 
Sep. 7  Btrees  [F99] 
Sep. 10  Heaps in External Memory  [FJKT99] 
Sep. 14  Discussion of Project 1A  
Sep. 17  Buffer Trees  [A95] 
Sep. 21  Batched Range Searching  [A95] 
Sep. 24  Selection, Permutation lower bound  [KL92] 
Sep. 28  Discussion of Project 1B  
Oct. 1  Sorting lower bound  [KL92] 
Oct. 5  Simulation of Parallel Algorithms: Random Permutations  [S98] 
Oct. 8  Random Permutations, Introduction to Orthogonal Range Searching  [S98],[ASV99] 
Oct. 12  Orthogonal Range Searching  [ASV99] 
Oct. 15  Orthogonal Range Searching  [ASV99] 
Oct. 19  Canceled  
Oct. 22  Canceled  
Oct. 26  Weight balanced Btrees  [ASV99] 
Oct. 29  Stabbing queries  [AV96] 
Nov. 2  Discussion of Project 2, Segment trees  
Nov. 5  Trapezoidal decomposition, Triangulation, Endpoint domination  [AVV95] 
Nov. 9  Endpoint domination  [AVV95] 
Nov. 12  Rtrees  [AHVV99] 
Nov. 16  SBtrees  [FG99] 
Nov. 19  SBtrees  [FG99] 
Nov. 23  String sorting  [AFGV97] 
Nov. 26  String sorting, Introduction to Project 3  [AFGV97] 
Nov. 30  Connected components  [ABW98] 
Dec. 3  Minimum spanning trees, Maximal matching, Breadth first search, Connected components  [ABW98],[MR99] 
Dec. 7  Connected components  [MR99] 
Dec. 10  Canceled  
Dec. 14  Canceled  
Dec. 17  Final discussion 