Re: [PATCH v2 0/8] pack-objects: Create an alternative name hash algorithm (recreated)

> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> This series creates a mechanism to select alternative name hashes using a
>> new --name-hash-version=<n> option. The versions are:
>>
>>   1. Version 1 is the default name hash that already exists. This option
>>      focuses on the final bytes of the path to maximize locality for
>>      cross-path deltas.
>>
>>   2. Version 2 is the new path-component hash function suggested by Jonathan
>>      Tan in the previous version (with some modifications). This hash
>>      function essentially computes the v1 name hash of each path component
>>      and then overlays those hashes with a shift to make the parent
>>      directories contribute less to the final hash, but enough to break many
>>      collisions that exist in v1.
>>
>>   3. Version 3 is the hash function that I submitted under the
>>      --full-name-hash feature in the previous versions. This uses a
>>      pseudorandom hash procedure to minimize collisions but at the expense of
>>      losing on locality. This version is implemented in the final patch of
>>      the series mostly for comparison purposes, as it is unlikely to be
>>      selected as a valuable hash function over v2. The final patch could be
>>      omitted from the merged version.
>>
>> See the patches themselves for detailed results in the p5313-pack-objects.sh
>> performance test and the p5314-name-hash.sh test that demonstrates how many
>> collisions occur with each hash function.
> 
> These do not sound like versions but more like variants to me,
> especially if one is expected to perform better than another in some
> cases and worse in some other cases.  Is it expected that JTan's hash
> to perform better than the original and current hash in almost all
> cases (I would not be surprised at all if that were the case)?