Alpha4 release status

BogDan bog_dan_ro at yahoo.com
Tue Jun 19 13:38:40 UTC 2012 

>
>So, if we use the new assets:/ schema, do we get all the performance improvements? 

Yes, only "assets:/" should do the job.

>Or, do other changes still need to be done to the library to get performance improvements?
>

No other changes are needed.

>
>Just clarifying :) Thanks for all your hard work.
>
>
>On Sun, Jun 17, 2012 at 3:58 AM, BogDan Vatra <taipanromania at gmail.com> wrote:
>
>Hello everyone,
>>
>>I have some good and bad news.
>>
>>I changed the atomics in order to make the safe, I chose the fifth
>>approach and it seems they are just a little bit slower, because it
>>has to do an extra function call. The good news are there is no ABI
>>break, so I can still play my favorite GPLv3 Qt game which I bought it
>>a few months ago :). No, I'm not crazy :)! I bought a GPLv3 game
>>because I like it! It also helped me a lot to test alpha4 branch. The
>>bad news is that the application start up is still slower comparing
>>with alpha3, this is because I've done a little hack in android assets
>>implementation to keep the compatibility with alpha3. But if the
>>assets access will be updated to alpha4, the start up is almost the
>>same. I'm not going to fix this problem now, because I don't have
>>enough time, after alpha4 is out, we'll focus on performance and
>>bugfixes only.
>>
>>
>>Cheers,
>>BogDan.
>>
>>
>>2012/6/15 Tyler Mandry <tmandry at gmail.com>:
>>
>>> I say try 5) and benchmark it.
>>>
>>> I understand that you're trying to keep backward compatibility, but for such
>>> fundamental and important changes, IMO it is far better to break the ABI now
>>> than to pay for it in the future. Besides, we are still in alpha, breaking
>>> the ABI should be considered a regular occurrence ;)
>>>
>>>
>>> On Sunday, June 10, 2012 12:15:12 PM UTC-7, BogDan wrote:
>>>>
>>>> Hi,
>>>>
>>>> Many thanks for kind words !
>>>>
>>>> Sadly, the magic happened :). The good news is that it was my fault,
>>>> the bad news it that my worst nightmare happened ... :(
>>>> After I write my first mail I begin to cherry-pick all my changes from
>>>> alpha4 and put them on top of alpha3 branch, then I spot a patch which
>>>> caught my attention, and I really hoped it's not the cause of this
>>>> problem, but it was ...
>>>> Some time ago somebody complained on this mailing list about the fact
>>>> that he could not be able to compile necessitas anymore using ndk-r7,
>>>> soon I discovered that the atomics functions where not exported
>>>> anymore in ndk-r7, then my nightmare began, first I post the problem
>>>> on android-ndk mailing list[1], then Google suggest me that I should
>>>> switch to gcc's built in atomics which I did[2]. I knew that the gcc
>>>> built in atomics are not the fastest in the world, but I never thought
>>>> that they are that bad. Android atomics support on necessitas is a
>>>> long story, which began more than a year ago, I'll try to make it
>>>> shorter for you :)
>>>> For the very first android atomics implementation, I used Qt's arm
>>>> atomics, but I had to switch to gcc built-in atomics (yes, the second
>>>> implementation was based on gcc atomics) because Qt's arm5 atomics
>>>> where useless for Android, I'll try to explain why: The problem is
>>>> that Qt's arm5 atomics are not SMP safe, so, is probable that your app
>>>> will crash on a dual-core device. arm5 is very important because it is
>>>> supported by all arm android devices, so it must be SMP safe. I
>>>> address this problem last year at QCS[3], and somebody offer to help,
>>>> but sadly nothing happened. So, I had to find a solution myself, GCC's
>>>> implementation is using a sort of memory barrier (a mutext or
>>>> something) to make it SMP safe, that why is so slow, then I discover
>>>> that google is providing atomics in libc, which they should be SMP
>>>> safe, so I switched to android atomics, then google change their mind
>>>> and now they are dropping the support, so I had to switch back to gcc.
>>>>
>>>> To "fix" this problem I see the following "solutions":
>>>> 1. Ignore Google warning and keep using android atomics.
>>>> 2. Stay with gcc atomics, but is too slow.
>>>> 3. Build Qt libs with fast atomics, but find a way to have safe
>>>> atomics for arm5.
>>>> 4. Build Qt libs with fast atomics, but use GCC atomics for apps.
>>>> 5. Build Qt libs with fast atomics, but don't make qt atomics inline
>>>> anymore, this way your apps will use what qt provides for that
>>>> platform. They will be a little by slower but they should be safe.
>>>> This is my favorite solution, but I afraid that it will break the ABI
>>>> ...
>>>>
>>>> It is safe to build Qt libs with fast atomics for arm5 because arm5
>>>> libs will be downloaded Ministro *only* on arm5 devices and AFAIK
>>>> there is no SMP arm5 device. The problem is that your apps are not
>>>> downloaded by Ministro :) and if they are built only using armv5 they
>>>> will be loaded by a SMP device and they will have problems, so arm5
>>>> atomics must be SMP safe.
>>>>
>>>> Anyway we have to address the problem once and for all !
>>>>
>>>> If any of you has any other Ideas please don't hesitate to share them with
>>>> us.
>>>> Also any comments/feedback will be very appreciated.
>>>>
>>>> Cheers,
>>>> BogDan.
>>>>
>>>>
>>>> [1]
>>>> https://groups.google.com/group/android-ndk/browse_thread/thread/a792d8392b01f389/ecbad8bb4981ed8d
>>>> [2]
>>>> http://commits.kde.org/android-qt/aa14a65fd29f20adb7aa22b354c975d76266bed1
>>>> [3] http://community.kde.org/Necessitas/Meetings/QtCS2011
>>>>
>>>>
>>>> 2012/6/10 Bruno Zerbo <bruno.zerbo at gmail.com>:
>>>> > Thanks BogDan for your work.
>>>> > cheers,
>>>> > Bruno
>>>> >
>>>> >
>>>> > 2012/6/10 BogDan Vatra <taipanromania at gmail.com>
>>>> >>
>>>> >> Hello folks,
>>>> >>
>>>> >>  Unfortunately I have more bad news regarding alpha4 release, I
>>>> >> manage to fix the OpenGL problem, but I discover another one. The
>>>> >> startup of all applications has slowdown a lot (2-4 times), the
>>>> >> problem is the difference between alpha3 and alpha4 is huge (1000+
>>>> >> patches). Alpha3 is based on Qt 4.8.0-rc and alpha4 is based on Qt
>>>> >> 4.8.2, to be sure the problem is not caused by me, I have to
>>>> >> cherry-pick all my changes and put them on top of alpha3, them, if is
>>>> >> not my fault the pain begins, I'll have to merge Qt 4.8.0, check, then
>>>> >> Qt 4.8.1, then Qt 4.8.2. This is going to be a very slow and painful
>>>> >> process which will take days (even weeks) so, I don't believe alpha4
>>>> >> will be out before QCS, unless a miracle happens and I'll found the
>>>> >> issue in the next days.
>>>> >>
>>>> >> Sorry for the bad news ...
>>>> >>
>>>> >> Cheers,
>>>> >> BogDan.
>>>> >>
>>>> >>
>>>> >> 2012/6/4 BogDan <taipanromania at gmail.com>:
>>>> >> > This http://files.kde.org/necessitas/installer/MinistroActivity.apk
>>>> >> > is
>>>> >> > the link to Ministro.
>>>> >> >
>>>> >> > BogDan.
>>>> >> >
>>>> >> >
>>>> >> > On Jun 4, 2:02 pm, BogDan Vatra <taipanroma... at gmail.com> wrote:
>>>> >> >> Hi everyone,
>>>> >> >>
>>>> >> >>  As you may know the alpha4 release is approaching, the plan is to
>>>> >> >> have it ready before Qt Contributors Summit. It is almost completed,
>>>> >> >> I
>>>> >> >> need a few days to polish the style plugin and Minitro and another
>>>> >> >> few
>>>> >> >> to add support for context menus.
>>>> >> >>
>>>> >> >>   A few days ago I pushed to Minnistro's "unstable" repository the
>>>> >> >> current alpha4 branch in order to check if the existing released
>>>> >> >> apps
>>>> >> >> are still working. Even we've made some heavy changes and even if I
>>>> >> >> warn you that it may break the compatibility with older versions, I
>>>> >> >> wanted alpha4 to be backward compatible with alpha3, it is also a
>>>> >> >> test
>>>> >> >> for Necessitas developers to see if we can keep our promise: to ship
>>>> >> >> releases which are backward compatible!
>>>> >> >>
>>>> >> >> If you want to try it yourself please follow the next two steps:
>>>> >> >>  - uninstall official Ministro and use this
>>>> >> >> onehttp://files.kde.org/necessitas/MinistroActivity.apk.
>>>> >> >>  - install and run Ministro configuration tool (from market) and
>>>> >> >> choose unstable repository.
>>>> >> >>
>>>> >> >> Don't forget that Ministro is not stable and it may crash/hang, if
>>>> >> >> you
>>>> >> >> encounter any problems please reply on this thread.
>>>> >> >>
>>>> >> >> Shorty after the repository was ready, I tried a few apps from
>>>> >> >> market
>>>> >> >> and two major problems pop up:
>>>> >> >> - The first problem was related to some missing symbols and was
>>>> >> >> caused
>>>> >> >> by compilation/linking flags.
>>>> >> >> - The second one is related to OpenGL and it seems to be caused by
>>>> >> >> the
>>>> >> >> merge with Qt 4.8.2.
>>>> >> >>
>>>> >> >> 1. Missing symbols problem: Android comes with almost no support for
>>>> >> >> C++, so to compile Qt we used (static) gnu-libstdc++.
>>>> >> >> Then I discovered that this was a big mistake (for more information
>>>> >> >> check Android NDK docs/CPLUSPLUS-SUPPORT.html "II.3. Static
>>>> >> >> runtimes:"
>>>> >> >> section).
>>>> >> >> We can not use link libstdc++ statically if we are using more than
>>>> >> >> one
>>>> >> >> shared libraries in a project. To fix this problem I had two
>>>> >> >> choices:
>>>> >> >>  - to use the shared libstdc++ implementation and to change all the
>>>> >> >> scripts in order to add it to ministro (1.2M).
>>>> >> >>  - to "embed" the whole library into QtCore library (it adds and
>>>> >> >> extra
>>>> >> >> 600K) but this change requires no additional changes.
>>>> >> >>
>>>> >> >> I choose the second one [1],[2] because it was safe and easy and
>>>> >> >> mostly because it didn't needed any other changes.
>>>> >> >> If anybody has something against this change speak now or forever
>>>> >> >> hold
>>>> >> >> your peace !
>>>> >> >>
>>>> >> >> I'd like to add exceptions and RTTI by default, if the size and
>>>> >> >> speed
>>>> >> >> will not be affected.
>>>> >> >>
>>>> >> >> 2. OpenGL problem: After I merged alpha4 branch with upstream Qt
>>>> >> >> 4.8.2, most of the OpenGL apps are not working anymore, I tried to
>>>> >> >> fix
>>>> >> >> it my self but I end up with a very ugly workarround. It seems that
>>>> >> >>
>>>> >> >>
>>>> >> >> "boolQGLContext::areSharing(constQGLContext*context1,constQGLContext*contex
>>>> >> >> t2)"
>>>> >> >> always returns false. I tried to trace the problem but with no luck
>>>> >> >> and I end up adding a super dirty workarround: on android,
>>>> >> >> "QGLContext::areSharing", will always returns true. I really don't
>>>> >> >> like it, so until we'll figure out what is wrong the release process
>>>> >> >> will stop ...
>>>> >> >>
>>>> >> >> Any help will on this matter be very appreciated !
>>>> >> >>
>>>> >> >> I've spot another minor problem with old assets support it was
>>>> >> >> caused
>>>> >> >> by "QString QDeclarativeTypeLoader::absoluteFilePath(const QString
>>>> >> >> &path)" I fixed it locally but I didn't had time to push the fix to
>>>> >> >> Minsitro's repository yet.
>>>> >> >> I'll keep you post with the progress and with any Ministro
>>>> >> >> repository
>>>> >> >> changes.
>>>> >> >>
>>>> >> >> Cheers,
>>>> >> >> BogDan.
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> [1]http://quickgit.kde.org/index.php?p=android-qt.git&a=commit&h=8c4c862...
>>>> >> >>
>>>> >> >>
>>>> >> >> [2]http://quickgit.kde.org/index.php?p=android-qt.git&a=commit&h=abe85f4...
>>>> >
>>>> >
>>
>
>
>
>-- 
>Tyler Mandry
>
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