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Re: [GSoC] Optimize mysql-test-runs - Results of new strategy


Hi Pablo,

On 10.08.2014 9:31, Pablo Estrada wrote:
Hello Elena,
You raise good points. I have just rewritten the save_state and load_state
functions. Now they work with a MySQL database and a table that looks like

create table kokiri_data  ( dict varchar(20), labels varchar(200), value
varchar(100), primary key (dict,labels));

Since I wanted to store many dicts into the database, I decided to try this
format. The 'dict' field includes the dictionary that the data belongs to
('upd_count','pred_count' or 'test_info'). The 'labels' field includes the
space-separated list of labels in the dictionary (for a more detailed
explanation, check the README and the code). The value contains the value
of the datum (count of runs, relevance, etc.)

Since the labels are space-separated, this assumes we are not using the
mixed mode. If we use mixed mode, we may change the separator (, or & or %
or $ are good alternatives).

Let me know what you think about this strategy to store into the database.
I felt it was the most simple one, while still allowing to do some querying
on the database (like loading only one metric or one 'unit'
(platform/branch/mix), etc). It may also allow to store many configurations
if necessary.

Okay, lets have it this way. We can change it later if we want to.

In the remaining time, you can do the cleanup, check documentation, and maybe run some last clean experiments with the existing data and different parameters (modes, metrics etc.), to have the statistical results with the latest code, which we'll use later to decide on the final configuration.



On Sat, Aug 9, 2014 at 8:26 AM, Elena Stepanova <elenst@xxxxxxxxxxxxxxxx>

Hi Pablo,

Thanks for the update. Couple of comments inline.

On 08.08.2014 18:17, Pablo Estrada wrote:

Hello Elena,
I just pushed a transaction, with the following changes:

1. Added an internal counter to the kokiri class, and a function to expose
it. This function can show how many update result runs and prediction runs
have been run in total, or per unit (an unit being a platform, a branch or
a mix of both). Using this counter, one can decide to add logic for extra
learning rounds for new platforms (I added it to the wrapper class as an

2. Added functions to load and store status into temporary storage. They
are very simple - they only serialize to a JSON file, but they can be
easily modified to fit the requirements of the implementation. I can add
this in the README. If you'd like for me to add the capacity to connect to
a database and store the data in a table, I can do that too (I think it

Yes, I think we'll have to have it stored in the database.
Chances are, the scripts will run on buildbot slaves rather than on the
master, so storing data in a file just won't do any good.

  would be easiest to store the dicts as json data in text fields). Let me
know if you'd prefer that.

I don't like the idea of storing the entire dicts as json. It doesn't seem
to be justified by... well... anything, except for saving a tiny bit of
time on writing queries. But that's a one-time effort, while this way we
won't be able to [easily] join the statistical data with, lets say,
existing buildbot tables; and it generally won't be efficient and easy to

Besides, keep in mind that for real use, if, lets say, we are running in
'platform' mode, for each call we don't need the whole dict, we only need
the part of dict which relates to this platform, and possibly the standard
one. So, there is really no point loading other 20 platforms' data, which
you will almost inevitably do if you store it in a single json.

The real (not json-ed) data structure seems quite suitable for SQL, so it
makes sense to store it as such.

If you think it will take you long to do that, it's not critical: just
create an example interface for connecting to a database and running *some*
queries to store/read the data, and we'll tune it later.


By the way, these functions allow the two parts of the algorithm to be
called separately, e.g.:

Predicting phase (can be done depending of counts of training rounds for
platform, etc..)
1. Create kokiri instance
2. Load status (call load_status)
3. Input test list, get smaller output
4. Eliminate instance from memory (no need to save state since nothing
changes until results are updated)

Training phase:
1. Create kokiri instance
2. Load status (call load_status)
3. Feed new information
4. Save status (call save_status)
5. Eliminate instance from memory

I added tests that check the new features to the wrapper. Both features
seem to be working okay. Of course, the more prediction rounds for new
platforms, the platform mode improves a bit, but not too dramatically, for
what I've seen. I'll test it a bit more.

I will also add these features to the file_change_correlations branch, and
document everything in the README file.


On Wed, Aug 6, 2014 at 8:04 PM, Elena Stepanova <elenst@xxxxxxxxxxxxxxxx>

  (sorry, forgot the list in my reply, resending)

Hi Pablo,

On 03.08.2014 17:51, Pablo Estrada wrote:

Hi Elena,

  One thing that I want to see there is fully developed platform mode. I


that mode option is still there, so it should not be difficult. I


did it myself while experimenting, but since I only made hasty and crude
changes, I don't expect them to be useful.

I'm not sure what code you are referring to. Can you be more specific on
what seems to be missing? I might have missed something when migrating


the previous architecture...

I was mainly referring to the learning stage. Currently, the learning
stage is "global". You go through X test runs, collect data, distribute
between platform-specific queues, and from X+1 test run you start
predicting based on whatever platform-specific data you have at the

But this is bound to cause rather sporadic quality of prediction, because
it could happen that out of 3000 learning runs, 1000 belongs to platform
while platform B only had 100, and platform C was introduced later, after
your learning cycle. So, for platform B the statistical data will be very
limited, and for platform C there will be none -- you will simply start
randomizing tests from the very beginning (or using data from other
platforms as you suggest below, which is still not quite the same as pure
platform-specific approach).

It seems more reasonable, if the platform-specific mode is used, to do
learning per platform too. It is not just about current investigation
activity, but about the real-life implementation too.

Lets suppose tomorrow we start collecting the data and calculating the
Some platforms will run more often than others, so lets say in 2 weeks
will have X test runs on these platforms so you can start predicting for
them; while other platforms will run less frequently, and it will take 1
month to collect the same amount of data.
And 2 months later there will be Ubuntu Utopic Unicorn which will have no
statistical data at all, and it will be cruel to jump into predicting
right away, without any statistical data at all.

It sounds more complicated than it is, in fact pretty much all you need
add to your algorithm is making 'count' in your run_simulation a dict
rather than a constant.

So, I imagine that when you store your metrics after a test run, you will
also store a number of test runs per platform, and only start predicting
for this particular platform when the count for it reaches the configured

Of the code that's definitely not there, there are a couple things that
could be added:
1. When we calculate the relevance of a test on a given platform, we


want to set the relevance to 0, or we might want to derive a default
relevance from other platforms (An average, the 'standard', etc...).
Currently, it's just set to 0.

I think you could combine this idea with what was described above. While
it makes sense to run *some* full learning cycles on a new platform, it
does not have to be thousands, especially since some non-LTS platforms
and go awfully fast. So, we run these no-too-many cycles, get clean
platform-specific data, and if necessary enrich it with the other
platforms' data.

2. We might also, just in case, want to keep the 'standard' queue for


we don't have the data for this platform (related to the previous

If we do what's described above, we should always have data for the
But if you mean calculating and storing the standard metrics, then yes --
since we are going to store the values rather than re-calculate them
time, there is no reason to be greedy about it. It might even make sense
calculate both metrics that you developed, too. Who knows maybe one day
we'll find out that the other one gives us better results.

  It doesn't matter in which order they fail/finish; the problem is, when
builder2 starts, it doesn't have information about builder1 results,
builder3 doesn't know anything about the first two. So, the metric for


X could not be increased yet.

But in your current calculation, it is. So, naturally, if we happen to
catch the failure on builder1, the metric raises dramatically, and the
failure will be definitely caught on builders 2 and 3.

It is especially important now, when you use incoming lists, and the
running sets might be not identical for builders 1-3 even in standard


Right, I see your point. Although if test_run 1 would catch the error,
test_run 2, although it would be using the same data. might not catch
same errors if the running set makes it such that they are pushed out
to lower relevance. The effect might not be too big, but it definitely


potential to affect the results.

Over-pessimistic part:

It is similar to the previous one, but look at the same problem from a
different angle. Suppose the push broke test X, and the test started
failing on all builders (platforms). So, you have 20 failures, one per


run, for the same push. Now, suppose you caught it on one platform but


on others. Your statistics will still show 19 failures missed vs 1


caught, and recall will be dreadful (~0.05). But in fact, the goal is
achieved: the failure has been caught for this push. It doesn't really
matter whether you catch it 1 time or 20 times. So, recall here should

be 1.

It should mainly affect per-platform approach, but probably the
one can also suffer if running sets are not identical for all builders.

Right. It seems that solving these two issues is non-trivial (the


table does not contain duration of the test_run, or anything). But we
keep in mind these issues.

Right. At this point it doesn't even make sense to solve hem -- in
real-life application, the first one will be gone naturally, just because
there will be no data from unfinished test runs.

The second one only affects recall calculation, in other words --
evaluation of the algorithm. It is interesting from theoretical point of
view, but not critical for real-life application.

  I fixed up the repositories with updated versions of the queries, as
as instructions in the README on how to generate them.

Now I am looking a bit at the buildbot code, just to try to suggest some
design ideas for adding the statistician and the pythia into the MTR
related classes.

As you know, we have the soft pencil-down in a few days, and the hard one
a week later. At this point, there isn't much reason to keep frantically
improving the algorithm (which is never perfect), so you are right not
planning on it.

In the remaining time I suggest to

- address the points above;
- make sure that everything that should be configurable is configurable
(algorithm, mode, learning set, db connection details);
- create structures to store the metrics and reading to/writing from the
- make sure the predicting and the calculating part can be called
- update documentation, clean up logging and code in general.

As long as we have these two parts easily callable, we will find a place
in buildbot/MTR to put them to, so don't waste too much time on it.



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