[Bf-committers] The Story Of My Attempts At Contributing Code To Blender

[lumpengnom at posteo.de]

Hi Ryan and Dalai,

I would like to chime in regarding the "thousands of collections" use 
case:
When importing CAD geometry it is very common to have a hierarchy of 
collections in the hundreds or thousands of collections.
Since this hierarchy is useful for organisational purposes it is often 
preferable to keep this hierarchy intact instead of spending time on 
re-organizing the scene.
A performance boost for scenes with lots of collections would therefore 
be very welcome.

Best Regards
Johannes (Lumpengnom)



Am 17.08.2021 06:41 schrieb Ryan Inch via Bf-committers:
> Hi Dalai,
> Thank you for looking into this and getting back to me with more
> specific details.
> 
> I think there may be a slight misunderstanding with how my patch is
> designed.  If by first matching user you mean the first layer
> collection in the tree, of a collection which has been linked to
> multiple layer collections, then my patch doesn't do this, it doesn't
> just take the first layer collection it comes across.  My patch walks
> through the layer collection tree and the collection tree at the same
> time, when there are no structural changes it should always keep the
> trees perfectly in sync, when there are structural changes it takes
> only the invalid layer collections (layer collections that have been
> either significantly moved, or removed) and then remaps or removes
> only those invalid layer collections (the rest are relinked as when
> there are no structural changes) by order so that the correct layer
> collection should always end up at the correct new position in the
> tree.  As far as I am aware there is no way for the order to change in
> a move, so it should always remap the layer collections successfully.
> 
> Note:  While figuring out a simple example to illustrate this, I did
> find and fix a small bug where some layer collections got missed, and
> I found that ASan had issues with the order I was deleting
> collections, so I fixed that too.  I guess this is why patch review is
> a thing. ;)
> 
> I've updated my diff with the fixes, but I would be very interested in
> hearing more about this problem that the studio ran into and that my
> patch didn't fix, and if it works now with the update.  If Bastien
> would like to chime in here, that would be great.  It's too bad he
> didn't mention it at the time, as it only took a couple days to fix,
> but better late than never.
> 
> Note2: When I updated my diff I found that I had missed a change
> unrelated to the syncing algorithm, so my performance metrics were
> slightly off.  The new metrics are:
>     296 microseconds to resync 1000 collections when configured so
> that each of the 1000 has 1 child. (2x faster than Bastien's)
>     294 microseconds to resync 1000 collections when configured as a
> flat list with all of the collections under the scene collection. (75x
> faster than Bastien's)
> 
> When I looked over Bastien's patch a couple performance improvements
> did come to mind, and I wouldn't necessarily mind working on them with
> him, however, I think that the overall method of mine has more
> inherent performance gains, and shouldn't be abandoned without a fair
> trial.
> 
> I too hope that communication can be improved so that situations like
> this don't arise in the future, and I'm here if you want any feedback
> on new communication guidelines, or whatever.  Without the missed
> communication, I think there could have been a highly performant
> solution merged into master months ago.
> 
> Speaking of missed communication, I noticed that you mentioned in
> blender.chat a desire to have unit tests included with the patch and
> that there is currently a lack of unit tests in core areas.  Now that
> I think about it, I agree it would be a good idea to have unit tests
> for layer collections (although I'm not very familiar with unit tests
> and would need some direction to create my own), but unfortunately,
> there was never any mention of them on any of my patches so I didn't
> consider them before.
> 
> Here is a simple test to show that my patch remaps the equivalent
> layer collection and not just the first that it comes across:
> 1. Create a set of collections like so:
>     Collection
>     - Collection 1
>     Collection 2
>     - Collection 1 (linked)
> 2. Turn off the exclude checkbox for Collection 1 under Collection 2
> 3. Move the excluded collection to before/above Collection.
> 4. See that the moved collection is still excluded.
> 
> Note3: This didn't work before I updated my patch with my bug fix, but
> works now that I've found and fixed it.
> 
> I know that it'll be somewhat of hassle looking into my patch again,
> but I think it's got the potential to be a really good contribution,
> and I hope you'll still consider it.  I also hope Bastien will
> contribute his thoughts because I'd like to work with everyone on
> this.
> 
> As a final note, I'm pushing a bit strongly for my patch because I
> think it will provide the greatest benefit to Blender (a 100%-7400%
> performance increase, in some situations, is no small thing), but if
> there is some inherent, insurmountable, flaw in the underlying design,
> then I will of course be willing to work with Bastien on his patch to
> provide the much needed performance improvements, because while the
> collection system may not have been designed with 1000s of collections
> in mind, it's a valid use case and one that I think is only impeded by
> some implementation details.
> 
> All the best,
> Ryan
> 
> 
> On 2021-08-13 06:00 AM, bf-committers-request at blender.org wrote:
>> Date: Thu, 12 Aug 2021 17:42:22 +0200
>> From: Dalai Felinto <dalai at blender.org>
>> To: bf-blender developers <bf-committers at blender.org>
>> Cc: Ryan Inch <mythologylover75 at gmail.com>
>> Subject: Re: [Bf-committers] The Story Of My Attempts At Contributing
>> 	Code To Blender
>> Message-ID:
>> 	<CAKD4fWex1zXZ1J9U4uVuN1nuaX1A5NbNWyFJgFAfDfoT72+pww at mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>> 
>> Hi Ryan,
>> More details about your specific patch (D9599).
>> 
>> The solution you found has some merits, however it is incomplete and
>> doesn't work as well as the one that we now have in master. More
>> specifically it doesn't account for cases when the collection is 
>> linked
>> inside more than one collection (it would just get the first matching 
>> user
>> of said collection).
>> 
>> This problem wasn't considered a priority until a related issue came 
>> up
>> (overrides resync in some production files). By then Bastien tried 
>> your
>> patch which didn't fix the problem. He then proceed to create his own
>> solution, which is what ended up being merged.
>> 
>> The use case of 9,000 collections is not one that was taken into
>> consideration for the solution. It simply doesn't represent the type 
>> of
>> scene the system is built for. That said this can be improved a bit. 
>> So if
>> you are interested on help this further please reach out to Bastien, 
>> he has
>> some ideas on how the code can iterate a bit faster on the 
>> collections. He
>> is also available if you need more clarifications on the shortcomes of 
>> your
>> patch.
>> 
>> If you need more clarifications let me know. All in all I hope we (the
>> development team) can improve the communication even further to 
>> prevent
>> situations like this one.
>> 
>> -Dalai-
>> --------------------------------------------------------------------
>> Dalai Felinto - dalai at blender.org - www.blender.org
>> Blender Development Coordinator
>> Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
>> 
>> 
>> Op wo 11 aug. 2021 om 10:25 schreef Dalai Felinto <dalai at blender.org>:
>> 
>>> Hi Ryan,
>>> Thanks for your email.
>>> 
>>> I will talk to Bastien to understand better the decision process for 
>>> this
>>> particular patch. See what caused your patch to be abandoned, and if 
>>> there
>>> is room for further performance improvements. I will get back to you 
>>> here.
>>> 
>>> Furthermore, you brought a few points that the Blender project has to
>>> improve:
>>> 
>>> * Communication of the modules agendas.
>>> * Module to be more open to contributors.
>>> * Patch review process (e.g., clear process or assigning, set 
>>> expectations
>>> upfront, better communication).
>>> 
>>> As a rule of thumb any developer who is driven to collaborate to 
>>> Blender
>>> overall agenda and shows the dedication and competence should be 
>>> welcomed
>>> into the modules. Even for modules where the bar is a bit higher, 
>>> such as
>>> the core module [1].
>>> 
>>> All in all this comes in in a good time. In a few weeks Thomas Dinges 
>>> will
>>> start helping to coordinate the online development community. And 
>>> this is a
>>> very clear use case of what he can look at to help for improvements.
>>> 
>>> Meanwhile as a general rule if a module is not working well this can 
>>> be
>>> escalated to the bf-admins [2]. As a last resource if someone think 
>>> that
>>> the bf-admins are not addressing things properly or in a fashionable 
>>> time,
>>> it can escalate further to Ton.
>>> 
>>> [1] -
>>> https://code.blender.org/2021/02/module-teams-for-core-blender-development/
>>> [2] - https://wiki.blender.org/wiki/Modules#Blender
>>> 
>>> Regards,
>>> -Dalai-
>>> --------------------------------------------------------------------
>>> Dalai Felinto - dalai at blender.org - www.blender.org
>>> Blender Development Coordinator
>>> Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
>>> 
>>> 
>>> Op wo 11 aug. 2021 om 01:17 schreef Ryan Inch via Bf-committers <
>>> bf-committers at blender.org>:
>>> 
>>>> To the core Blender developers.
>>>> Hello again, Collection Manager dev here.
>>>> Let me start off by saying that I care a lot about Blender, it's 
>>>> been a
>>>> huge influence on my life and an inspiring story of the little DCC 
>>>> app
>>>> that could, and I want nothing but the best for it. So it highly 
>>>> saddens
>>>> me that I feel I need to write this email.
>>>> 
>>>> I've been a part of the Blender community and writing add-ons for it 
>>>> for
>>>> eight years and a user of Blender for even longer.  I love the power 
>>>> it
>>>> gives me to create, and have always tried to give back with what I 
>>>> have
>>>> to give (Unfortunately, money is not one of those ways, so I have
>>>> contributed code, feedback, and support instead).
>>>> 
>>>> In 2019 I separated the Collection Manager out of a larger add-on 
>>>> and
>>>> submitted it to be included in Blender as a bundled add-on on the 
>>>> advice
>>>> of Brendon Murphy (meta-androcto).  Soon after my submission, I was
>>>> contacted by Paul Kotelevets (1D_Inc) who expressed the short 
>>>> comings of
>>>> the current collections system for complex scene setup and precise
>>>> modeling that requires multiple reference images.  Together, along 
>>>> with
>>>> others who gave feedback, we have advanced the usability of Blender 
>>>> for
>>>> complex setups and increased the capabilities of the new collection
>>>> system.  When I started this project I assumed that it would be 
>>>> highly
>>>> welcomed, because collections were one of the pillars of the 2.8
>>>> project, however, it was mostly ignored.  Still, I continued on with 
>>>> the
>>>> project because it was useful to me and was essential to others for
>>>> their jobs.
>>>> 
>>>> In the year and a half I've worked on the project, I've become 
>>>> pretty
>>>> familiar with the python side of collections and layer collections, 
>>>> but
>>>> during that time I ran into problems that I thought would be better
>>>> solved on the C side of Blender, so I spent ~6 months familiarizing
>>>> myself with layer collections and attempting to solve some of the
>>>> problems I'd run into, and then ultimately trying to stabilize layer
>>>> collections as a first step to further improvements.  I submitted 
>>>> three
>>>> patches during this time, one of which went nowhere (and rightly 
>>>> so),
>>>> one of which was a draft and that I used to ask for help when stuck 
>>>> (to
>>>> which was replied: Thanks for the patch, but it's up to you to 
>>>> present a
>>>> working code, otherwise it's likely a loss of time for 
>>>> everybody...),
>>>> and then a final one, which did contain working code.
>>>> 
>>>> I submitted the final patch on November 18th 2020 and assigned 
>>>> Bastien
>>>> Montagne, Brecht Van Lommel, and Dalai Felinto as reviewers; two 
>>>> months
>>>> later I updated the patch to the latest master and linked a good 
>>>> test
>>>> file I had made; ~2 weeks after that, Bastien responded that the 
>>>> patch
>>>> hadn't been forgotten and that he'd just had a lot on his plate; a 
>>>> few
>>>> days after this Hans Goudey (HooglyBoogly) reviewed the patch and
>>>> provided some really good comments (he didn't have to do this and 
>>>> I'm
>>>> really grateful to him), which I then addressed a couple weeks later 
>>>> (I
>>>> had been busy and things didn't seem urgent); three months later I
>>>> updated the patch to the latest master again; and then almost two 
>>>> months
>>>> after that it was abandoned by Bastien who had apparently just 
>>>> committed
>>>> his own solution.
>>>> 
>>>> As you might imagine, this was fairly distressing to me as I had put 
>>>> a
>>>> lot of time and effort into creating and then maintaining it.  I had
>>>> been content to be patient and not push for my patch, because I 
>>>> thought
>>>> it was of a low priority and I knew from various sources of Blender
>>>> communication that Bastien had been very busy and I didn't want to 
>>>> add
>>>> to the stress he was under.  So, after the patch was closed, I 
>>>> looked
>>>> into the one that replaced it and at Bastien's weekly reports to try 
>>>> and
>>>> figure out what had happened.
>>>> 
>>>> On inspection of Bastien's weekly reports, I found that he had been
>>>> working on his own solution for a month or so, but I hadn't 
>>>> connected
>>>> the dots because I thought he was working on stuff for library 
>>>> overrides
>>>> and that if he had needed something to preserve layer collections he
>>>> would have used the already working code that had been sitting in 
>>>> the
>>>> patch tracker for six months (or if a different direction was 
>>>> required,
>>>> told me and brought me onboard with developing the new patch).  And 
>>>> when
>>>> I looked at the patch that replaced mine, I found a comment by 
>>>> Brecht
>>>> saying it was "Great to see this tackled.", as if now that a "real"
>>>> programmer was working on it, it was suddenly much more important 
>>>> and
>>>> welcomed.
>>>> 
>>>> There are two issues here, with the first being how everything was
>>>> handled, the lack of communication and the disregard for the time I
>>>> spent attempting to contribute.  I have seen in official Blender
>>>> communications that one of the goals of Blender is to onboard new
>>>> developers, this is a perfect example of how not to do that. 
>>>> Campbell
>>>> Barton once said something in IRC about GSoC students that I have 
>>>> always
>>>> found inspiring:
>>>> 
>>>> "Typically for students who don't know what they want they ask a lot 
>>>> of
>>>> Q's... and never get involved.
>>>> (sounds a bit negative... just my experience tho)
>>>> Basically they waste our time.
>>>> People who are motivated don't wait for others to tell them what to 
>>>> do,
>>>> they start interesting projects themselves."
>>>> 
>>>> Now I'm not a GSoC student, but I started an interesting project, 
>>>> and
>>>> filled a gap that the core developers didn't have the time to 
>>>> address.
>>>> I didn't ask a lot of questions, because I'm pretty good at figuring
>>>> things out on my own, and I attempted to get involved. When I 
>>>> started, I
>>>> expected to be welcomed and onboarded by a great open source project
>>>> that was in need of more contributors and that I could work with to
>>>> improve a tool I care deeply about, but what I found was a project 
>>>> that
>>>> paid little attention to my contributions, did nothing to onboard 
>>>> me,
>>>> seems to care little for community contributions, and was mostly
>>>> unwilling to work with me.
>>>> 
>>>> The second issue here is with the code of the patch (D12016) that 
>>>> was
>>>> approved over mine (D9599).  While as far as I can tell, they are
>>>> functionally equivalent, Bastien's is much slower than mine, 
>>>> especially
>>>> when it comes to many layer collections under one parent.  From my 
>>>> tests
>>>> (debug, lite build, with Bastien's CLOGGING removed so as to match 
>>>> my
>>>> patch) the average time it took to resync 1000 collections when
>>>> configured so that each of the 1000 had 1 child was 612 microseconds 
>>>> for
>>>> Bastien's and 261 microseconds for my patch.  That's almost 2.5 
>>>> times
>>>> slower for his patch.  When the 1000 collections were configured as 
>>>> a
>>>> flat list under the scene collection, Bastiens took on average 22290
>>>> microseconds, while mine, on average, took only 252 microseconds.
>>>> That's almost 88.5 times slower for his patch.
>>>> 
>>>> You may be thinking that 1000 collections is unrealistically high 
>>>> and
>>>> that no one actually uses that many, but Paul Kotelevets (a diamond
>>>> level sponser, BTW) has told me that he regularly uses 7-9,000
>>>> collections in his work, so my test case is on the low side and the
>>>> performance costs of Bastien's patch will be even greater than what 
>>>> I
>>>> have outlined here.
>>>> 
>>>> I believe the performance problems with Bastien's patch stem mainly 
>>>> from
>>>> three places, the BLI_findptr which is used to check whether the 
>>>> layer
>>>> collection is valid as a child when generating the layer collection 
>>>> tree
>>>> wrapper with additional data, the method that is used when searching
>>>> through the wrapper, and the fact that each layer collection has to 
>>>> be
>>>> searched out from the wrapper, even when it is already in sync with 
>>>> the
>>>> collection tree.  The problem with all this searching is that for 
>>>> each
>>>> collection it tries to find under the current parent it has to loop 
>>>> over
>>>> all the previous collections under that parent, and this happens in 
>>>> 2
>>>> distinct areas.  And I believe this is also why it's so much slower 
>>>> when
>>>> all the collections are under one parent.
>>>> 
>>>> I think the reason mine is so much faster is that it does much less
>>>> searching.  My patch processes the layer collection tree in a depth
>>>> first search and finds only the invalid layer collections and stores
>>>> them in order, then the collection tree and layer collection tree 
>>>> are
>>>> walked through in tandem, re-linking the valid layer collections as 
>>>> it
>>>> goes, moving the invalid layer collections to their new positions 
>>>> when
>>>> needed, and then removing the invalid layer collections from the
>>>> original processed list after they've been added to the new layer
>>>> collection tree.  As little searching as possible is done, with the
>>>> initial order of the layer collections, the fact that they are 
>>>> invalid,
>>>> and the fact that the collection associated with that layer 
>>>> collection
>>>> matches the collection in the collection tree provides the needed 
>>>> data
>>>> to relink them successfully.
>>>> 
>>>> I will admit that there's always the possibility that my patch 
>>>> doesn't
>>>> handle some corner case, but nothing was identified in my own 
>>>> testing or
>>>> the review given to my patch, so I think it's safe to say the only
>>>> difference between the two is the underlying method, the 
>>>> performance,
>>>> and the authors.
>>>> 
>>>> Given what has happened I'd like to just wash my hands of this and
>>>> forget wasting all of our time with me trying to contribute to the C
>>>> side of Blender and just stick to developing my add-on for those 
>>>> that
>>>> rely on it, but I can't, the performance implications are too large 
>>>> and
>>>> I can't in good conscience ignore this.  I'm willing to try and work
>>>> with you on this, whether that's with my patch, or on Bastien's to
>>>> improve his patch's performance (if it is uncovered that there is 
>>>> some
>>>> unsolvable limitation with mine), but I hope I have conveyed that a 
>>>> much
>>>> better outcome with much less work for all parties could have been
>>>> achieved had I been worked with, instead of around.
>>>> 
>>>> Sincerely yours,
>>>> an offboarded developer.
>>>> 
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