Talk:Cache-oblivious algorithm

This article is within the scope of WikiProject Computer science, a collaborative effort to improve the coverage of Computer science related articles on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.Computer scienceWikipedia:WikiProject Computer scienceTemplate:WikiProject Computer scienceComputer science articles

Low

This article has been rated as Low-importance on the project's importance scale.

Things you can help WikiProject Computer science with:

Here are some tasks awaiting attention:

Article requests :
- Requested articles/Applied arts and sciences/Computer science, computing, and Internet
Cleanup :
- Computer science articles needing attention
- Computer science articles needing expert attention
Copyedit :
- Computing
Expand :
- Computer science
Infobox :
- Computer science articles without infoboxes
Maintain :
- Timeline of computing 2020–present
Photo :
- Find pictures for the biographies of computer scientists (see List of computer scientists)
- Computing articles needing images
Stubs :
- Computer science stubs
Unreferenced :
- WikiProject Computer science/Unreferenced BLPs
Project-related :
- Tag all relevant articles in Category:Computer science and sub-categories with {{WikiProject Computer science}}

"This can be implemented in practice with the Least Recently Used policy, which is shown to be within a factor of 2 of the offline optimal replacement strategy."

I wrote this, but in hindsight I think it's wrong. The Move-To-Front heuristic is 2-optimal, but I'm not sure if that's equivalent to LRU. Seems not ...

Vecter 23:35, 7 June 2007 (UTC)[reply]

No, it's basically correct. The following lemma is proved in the Frigo paper from the references:

Lemma 12. Consider an algorithm that causes Q'(n;Z,L) cache misses on a problem of size n using a (Z, L) ideal cache. Then, the same algorithm incurs Q(n;Z,L) ≤ 2Q'(z;Z/2,L) cache misses on a (Z,L) cache that uses LRU replacement.

Note that, technically, you need an LRU cache of twice the size of the optimal-replacement cache to simulate it within a factor of two.

—Steven G. Johnson 16:10, 8 June 2007 (UTC)[reply]

cache-oblivious unrolled linked lists

"it is possible to design a variant of unrolled linked lists which is cache-oblivious" is false. The closest thing is the packed-memory array, but its append is slow. Normal and unrolled linked lists have constant time append. —Preceding unsigned comment added by 190.135.57.152 (talk) 00:10, 27 May 2010 (UTC)[reply]