Re: [PATCH 0/9] Prefix-compress on-disk index entries

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On Thu, Apr 5, 2012 at 4:44 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Nguyen Thai Ngoc Duy <pclouds@xxxxxxxxx> writes:
>
>> On Wed, Apr 4, 2012 at 5:53 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
>> ...
>> I wonder what causes user time drop from .29s to .13s here. I think
>> the main patch should increase computation, even only slightly, not
>> less.
>
> The main patch reduced the amount of the data needs to be sent to the
> machinery to checksum and write to disk by about 45%, saving both I/O
> and computation.

I hacked together a quick patch to try predictive coding the other
fields of the index. I got a further 34% improvement in size over
this series. Patches to come. I just used the previous cache entry as
the predictor and reused varint.h together with zigzag encoding[1].

That's a total improvement in size over v2 of 62%.

[1] https://developers.google.com/protocol-buffers/docs/encoding#types
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