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From Klaus Ma <klaus1982...@gmail.com>
Subject Re: Review Request 43635: Changed scalar resources to use fixed-point internally.
Date Wed, 17 Feb 2016 00:30:58 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/43635/#review119382
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docs/attributes-resources.md (line 7)
<https://reviews.apache.org/r/43635/#comment180724>

    Any related to this patches?



docs/attributes-resources.md (line 39)
<https://reviews.apache.org/r/43635/#comment180725>

    There seems two space before "Those are used to ..." in review board; but it's OK drop
this issues if it's one in the code.



include/mesos/mesos.proto (line 513)
<https://reviews.apache.org/r/43635/#comment180726>

    Remove one space before "Any additional precision"



src/common/values.cpp (line 52)
<https://reviews.apache.org/r/43635/#comment180719>

    remove empty line.



src/common/values.cpp (line 59)
<https://reviews.apache.org/r/43635/#comment180729>

    Replace 1000 with const integer



src/common/values.cpp (line 60)
<https://reviews.apache.org/r/43635/#comment180730>

    Regarnding `lround`, it maybe overcommit resources, if framework keep launching task with
smaller CPU usage; I'd suggest to discard the additional precission directly (e.g. 1.2345
-> 1.234). If there's any idle resources because of discarding, oversubscription will help.
    
    And we need to reject operation request with small resources which is handled in MESOS-1807.



src/common/values.cpp (line 61)
<https://reviews.apache.org/r/43635/#comment180717>

    Should we `setprecision`?



src/common/values.cpp (line 67)
<https://reviews.apache.org/r/43635/#comment180723>

    Let's add check on overflow; it will be helpful if scalar value was big. Scalar is a general
type, there maybe used with a big value, e.g. total size of distributed filesystem.



src/tests/resources_tests.cpp (line 23)
<https://reviews.apache.org/r/43635/#comment180731>

    Seems those two headers are not necessary.


- Klaus Ma


On Feb. 17, 2016, 7:29 a.m., Neil Conway wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/43635/
> -----------------------------------------------------------
> 
> (Updated Feb. 17, 2016, 7:29 a.m.)
> 
> 
> Review request for mesos, Joris Van Remoortere and Michael Park.
> 
> 
> Bugs: MESOS-4687
>     https://issues.apache.org/jira/browse/MESOS-4687
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Scalar resource values are represented using floating point. As a result, users
> could see unexpected results when accepting offers and making reservations for
> fractional resources: values like "0.1" cannot be precisely represented using
> standard floating point, and the resource values returned to frameworks might
> contain an unpredictable amount of roundoff error.
> 
> This commit adjusts the master to use fixed-point when doing internal
> computations on scalar resource values. The fixed-point format only supports
> three decimal digits of precision: that is, fractional resource values like
> "0.001" will be supported, but "0.0001" will not be.
> 
> 
> Diffs
> -----
> 
>   docs/attributes-resources.md 818da8ab0c672144b02f526b2b805cf0505d2c7e 
>   docs/upgrades.md 4f30d725c6ed28c09a1c5528fd4193c3f06b2d93 
>   include/mesos/mesos.proto e24d3e03a7dc7c6bfd07f34531cb593fe4925646 
>   include/mesos/v1/mesos.proto d909e60ddfd8e3ba2075f82c372edde04cd99d54 
>   src/common/resources.cpp 5d731870542166cec11f9956ccdf16207b2d22cc 
>   src/common/values.cpp c64407bc97ad858300f4661d616e0480920fc541 
>   src/master/allocator/mesos/hierarchical.cpp a9d2c23162892e22220f97d89a076d2311091d91

>   src/tests/resources_tests.cpp 96864c3945729fe33be8b243b9c826fb12e90eff 
>   src/v1/resources.cpp 207eb61d6a6d03d314539d42751cac65fcffa9af 
>   src/v1/values.cpp 58ea9875804bf0287855a1e9855855e5e54de4c4 
> 
> Diff: https://reviews.apache.org/r/43635/diff/
> 
> 
> Testing
> -------
> 
> make check
> 
> Manually verified that some of the floating point oddities in https://issues.apache.org/jira/browse/MESOS-4071
do not occur when this patch is applied, although I wasn't able to reproduce the crash described
in that ticket.
> 
> REVIEW NOTES:
> 
> * We don't currently emit a warning when discarding additional digits of precision from
input scalar resource values. Should we? That would require identifying all the points where
a resource value is seemed to be "user-provided", and also runs the risk of generating a ton
of log messages when an old framework is used.
> * Similarly, if the user gives us a resource value and we don't do anything to it, we
won't discard any additional precision that appears in the value -- the precision only gets
discarded when we apply an operator like `+` or `-`. Unclear if we should trim additional
precision from all scalar resource values more aggressively.
> 
> 
> Thanks,
> 
> Neil Conway
> 
>


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