From: Nicolas Pitre <nico@cam.org>
Date: Thu, 29 Jun 2006 16:35:36 GMT
Subject: Re: [RFC] Cache negative delta pairs
Message-ID: <Pine.LNX.4.64.0606291233120.1213@localhost.localdomain>
In-Reply-To: <Pine.LNX.4.64.0606291053280.1213@localhost.localdomain>

On Thu, 29 Jun 2006, Nicolas Pitre wrote:

> And this can be pushed even further by just including the sha1 of the 
> victim object inside the list of objects therefore computing a hash of 
> all objects (the victim and the window) for which no delta results. The 
> cache is therefore a list of hash values corresponding to bad 
> victim+window combinations.
> 
> So given my GIT repository such a cache would be 7610 * 40 = 304400 
> bytes if we stick to the full 40 bytes of sha1 to hash bad combinations.

Correction: the 40 bytes figure is for _ascii_ representation of sha1 
values.  The cache doesn't need ascii and therefore this number can be 
reduced by half.


Nicolas