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From Benjamin Bannier <benjamin.bann...@mesosphere.io>
Subject Re: Review Request 69819: Added equality operator for `ResourceQuantities`.
Date Thu, 31 Jan 2019 12:29:28 GMT


> On Jan. 28, 2019, 8:49 p.m., Benjamin Mahler wrote:
> > When we added `ResourceQuantities`, we wanted to support two use cases:
> > 
> > ```
> > guarantees: absent == 0    (i.e. zero_by_default)
> >     limits: absent == +inf (i.e. inf_by_default)
> > ```
> > 
> > This is why zeros are currently stored (unlike `Resources` objects, where they are
removed): having the ability to distinguish between 0 and absent allows us to support both
use cases. However, the introduction of equality and containment operations are not so obvious:
> > 
> > ```
> >    equality: the approach in this patch is providing inf_by_default equality semantics
AFAICT
> > containment: the approach in the subsequent patch is providing neither zero_by_default
or inf_by_default equality semantics
> > ```
> > 
> > I think that in order to introduce equality and containment, we may have to address
some earlier feedback on `ResourceQuantities`, which was to require a contruction-time choice
between `ZERO_BY_DEFAULT` and `INF_BY_DEFAULT` semantics. This would be stored as a variable
in order to determine (1) whether to store zeros, (2) how to evaluate equality and containment
between two quantities.
> > 
> > Thoughts?

Yes, that makes sense. I am still unsure whether one should build limit- or guarantee-specific
functionality into `ResourceQuantities` though as having a light-weight building block for
more involved semantics, e.g., around quotas.

I am discarding this patch and https://reviews.apache.org/r/69820/ for now as they are not
needed anymore.


- Benjamin


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https://reviews.apache.org/r/69819/#review212390
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On Jan. 29, 2019, 5:20 p.m., Benjamin Bannier wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/69819/
> -----------------------------------------------------------
> 
> (Updated Jan. 29, 2019, 5:20 p.m.)
> 
> 
> Review request for mesos, Benjamin Mahler and Meng Zhu.
> 
> 
> Bugs: MESOS-9523
>     https://issues.apache.org/jira/browse/MESOS-9523
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> This patch adds an `operator==` for `ResourceQuantities`. The operator
> is declared as a `friend` of `ResourceQuantities` so we can directly
> compare the two `ResourceQuantities::quantities` which can be less
> expensive.
> 
> 
> Diffs
> -----
> 
>   src/common/resource_quantities.hpp 11eb426104577bbbbb7977c2307df3e4917085cd 
>   src/common/resource_quantities.cpp 320983929cd7d14973c4b98d6ed5338de690ff5f 
> 
> 
> Diff: https://reviews.apache.org/r/69819/diff/2/
> 
> 
> Testing
> -------
> 
> `make check`
> 
> 
> Thanks,
> 
> Benjamin Bannier
> 
>


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