Re: [Gnu-arch-users] [PATCH] arch speedups on big trees

[Andrew Suffield]

On Fri, Dec 19, 2003 at 03:46:22PM -0800, Tom Lord wrote:
> 
>     > From: Andrew Suffield <address@hidden>
> 
>     >> Such optimizations require a fairly heavy proof before we can
>     >> trust them: they must prove that the apply_changeset algorithm
>     >> is invarient under them.  You haven't offered such a proof for
>     >> your variation and, in fact, your proposal to specially
>     >> consider only modified or deleted files is flat out wrong.
> 
>     > What's wrong with it?
> 
> Who knows the full list of things that are wrong with it but a subset
> of that list includes consideration of adds (to avoid redundant adds)
> and consideration of renames (both the things being renamed and their
> (recursively) containing directories, bearing in mind that the
> changeset is not guaranteed but is permitted to contain index entries
> for those containing directories).

Sure, renames would probably have to be treated like adds, and cause a
full scan (although I don't know that for sure, it's not so
obviously-safe so I'm not prepared to go there).

It seems fairly obvious to me that deletes and file-patches are safe
though: they operate only on a single logical file, and if we know
what the path to that file is, why do we care where all the other
files are?

I find a demand for proof of this rather like a demand for proof that
1 + 2 == 3 - it's so obviously true that I'm not sure how to start,
and the request makes me wonder if an axiom is missing or rejected.

-- 
  .''`.  ** Debian GNU/Linux ** | Andrew Suffield
 : :' :  http://www.debian.org/ |
 `. `'                          |
   `-             -><-          |

signature.asc
Description: Digital signature