From: Geert Bosch <bosch@adacore.com>
Date: Sat, 22 Apr 2006 12:35:14 GMT
Subject: Re: RFC: New diff-delta.c implementation
Message-ID: <6794F5B2-A277-4CD9-9BA8-509F86378E68@adacore.com>
In-Reply-To: <7v7j5hkglq.fsf@assigned-by-dhcp.cox.net>


On Apr 22, 2006, at 07:13, Junio C Hamano wrote:
> (Please line-wrap sensibly).
Apologies. I'm using a broken mailer, which insists
on breaking longish lines. I'll try to avoid this.

> I think we tried that with Nico/Davide's delta already, and IIRC
> we had mixed results.
>
> It really depends on how big an index for a source is.  Keep
> in mind that we keep --window (default=10) of the source
> text in-core, and you are suggesting to keep index in-core
> as well, so we need to take memory pressure into account.
The point is that if we do the following comparisons:

   diff A B
   diff A C
   diff A D

then we should keep A and its index in core for all
three comparisons. Discarding and recreating can never
be better :)
> Having said that, the initial number you posted suggests the
> algorithm is very fast, in which case reusing index may not
> matter.  We will see ;-).

BTW, after applying the obvious fixes, I get the following
message:
potomac%./git-pack-objects --no-reuse-delta --stdout <lst
Generating pack...
Done counting 16984 objects.
Deltifying 16984 objects.
100% (16984/16984) done
fatal: delta size changed

Is this expected now I have a different algorithm?

   -Geert