Lecture 15

Learning objectives

After this class, you should be able to:

1. Explain the ideal cache model.
2. Derive the cache complexity of the two simple matrix multiplication algorithms discussed in class, and of the cache aware and cache oblivious algorithms discussed in class.
3. Given an algorithm, derive its cache complexity.
4. Given an algorithm that is cache-inefficient, modify it to make it more efficient.

Reading assignment

1. Handout on cache oblivious algorithms.
2. Review Quicksort (CLR Chapter 7).

Exercises and review questions

• Questions on current lecture's material
  1. If matrices were stored in column major order, then show two simple algorithms, one which has a cache complexity of theta(n³) and one with cache complexity of theta(n³/L).

• Questions on next lecture's material
  1. Explain how quicksort would sort the following list, with the first element chosen as the pivot each time: 1, 2, 3, 4, 5, 6, 7, 8.