From: Ramsay Jones <ramsay@ramsayjones.plus.com>
Date: Tue, 03 Apr 2018 23:17:06 GMT
Subject: Re: [PATCH 2/6] commit: add generation number to struct commmit
Message-ID: <08d3c9dd-3589-5c1c-4cea-982e8ed28f3e@ramsayjones.plus.com>
In-Reply-To: <20180403182800.GA8377@sigill.intra.peff.net>



On 03/04/18 19:28, Jeff King wrote:
> On Tue, Apr 03, 2018 at 11:05:36AM -0700, Brandon Williams wrote:
> 
>> On 04/03, Derrick Stolee wrote:
>>> The generation number of a commit is defined recursively as follows:
>>>
>>> * If a commit A has no parents, then the generation number of A is one.
>>> * If a commit A has parents, then the generation number of A is one
>>>   more than the maximum generation number among the parents of A.
>>>
>>> Add a uint32_t generation field to struct commit so we can pass this
>>
>> Is there any reason to believe this would be too small of a value in the
>> future?  Or is a 32 bit unsigned good enough?
> 
> The linux kernel took ~10 years to produce 500k commits. Even assuming
> those were all linear (and they're not), that gives us ~80,000 years of
> leeway. So even if the pace of development speeds up or we have a
> quicker project, it still seems we have a pretty reasonable safety
> margin.

I didn't read the patches closely, but isn't it ~20,000 years?

Given that '#define GENERATION_NUMBER_MAX 0x3FFFFFFF', that is. ;-)

ATB,
Ramsay Jones