On 5/22/2019 2:29 PM, Jakub Narebski wrote:
> Derrick Stolee <stolee@xxxxxxxxx> writes:
>> On 5/20/2019 7:27 PM, Jakub Narebski wrote:
> Restating it yet again:
>
> A. corrected_date(C) = max(committer_date(C),
> max_P(committer_date(P) + offset(P)) + 1)
>
> B. offset(C) = max(corrected_date(C) - committer_date(C),
> max_P(offset(P)) + 1)
The problem with this definition is that it "defines" the corrected date, and
then _adjusts_ it by updating the offset. I consider
corrected_date(C) = committer_date(C) + offset(C)
to be part of the definition. You could restate the definition as follows:
corrected_date = max(committer_date(C) + max_P(offset(P)) + 1,
max_P(corrected_date(P)))
or, equivalently
corrected_date = max(committer_date(C) + max_P(offset(P)) + 1,
max_P(committer_date(P) + offset(P)))
This definition, in a single step, satisfies the conditions below:
>
>> The final definition needs two conditions on the offset of a commit C for
>> every parent P:
>>
>> 1. committer_date(C) + offset(C) > committer_date(P) + offset(P)
>> 2. offset(C) > offset(P)
Plus, the "+ 1" in the first step takes into account that "0" is a special offset
value in the commit-graph file format meaning "not computed".
> Well, we should check/test if performance benefits of "offset date"
> ("corrected date with rising offset") truly holds.
Yes, a full performance test will be required. I have full confidence that the
monotonic offset requirement will have only positive effect. That is, it will
not affect the case where committer-date was better than generation number, but will
help the cases where all the committer-dates are equal.
Thanks,
-Stolee
