Re: Sha1 lookup and GIT_USE_LOOKUP

[Marc Pegon <pegon.marc@gmail.com>]

On Wed, Jun 8, 2011 at 8:55 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Marc Pegon <pegon.marc@gmail.com> writes:
>
>> Since this environment variable is not set by default, git will always
>> use a simple binary search, won't it ?
>
> Yes.
>
>> Also, when searching for a sha1 given a sha1 prefix, among packed
>> objects, find_short_packed_object also does a simple binary search.
>> Wouldn't it be simpler to just use the sha1_entry_pos method ?
>
> Unknown ;-).
>
> The environment variable is there exactly for people like you who are
> interested in finding out which one yields better performance by
> benchmarking.  Once we can get a convincing result, we can either
> deprecate the more involved sha1_entry_pos() if it turns out to be not
> worth it, or we can always use it if it turns out to be significantly
> better.

Perhaps we could compare the two methods by counting for each one the
average number of iterations it takes to find an object in a pack.
But anyways, I guess GIT_USE_LOOKUP should also have an influence on
the method used to find an object given a sha1 prefix, and the code
that does a simple binary search should not be duplicated as it is
now, right ?

> Thanks.
>