[Imstk-developers] high-speed thread in iMSTK

Thu Jun 22 16:26:15 EDT 2017

"use trylock and come back later to the mesh which was already locked" -
what I mean by this was to first do trylock on all the meshes a thread
needs to update, and then do regular lock (which will put the thread into
the wait queue) for each mesh for which trylock failed. Once the other
thread releases the lock, this thread will awaken and start updating the
mesh.

Regards

Dženan Zukić, PhD, Senior R&D Engineer, Kitware (Carrboro, N.C.)

On Thu, Jun 22, 2017 at 4:00 PM, Milef, Nicholas Boris <milefn at rpi.edu>
wrote:

> The problem with that is that if one thread runs faster than another, then
> it might not be updated on a certain thread. For instance, if the physics
> thread keep acquiring the mesh data, then the mesh data will never update
> on the render thread (or vice-versa).
>
> What if we used a job-based approach? That way we would only need to lock
> the job submission and not the mesh data. I'm trying to think ahead for
> when we move normal computation or mesh interpolation to another thread
> (more times for contention). Logging is already on another thread, so that
> adds even more contention if you try to print mesh data.
>
> http://seanmiddleditch.com/multi-threaded-game-engines/
> ------------------------------
> *From:* Dzenan Zukic [dzenan.zukic at kitware.com]
> *Sent:* Thursday, June 22, 2017 3:50 PM
> *To:* Milef, Nicholas Boris
> *Cc:* Zhaohui Xia; imstk-developers at imstk.org
>
> *Subject:* Re: [Imstk-developers] high-speed thread in iMSTK
>
> Each mesh could have its own mutex, which needs to be obtained by the
> thread which wants to write it. Or if a thread can do something else, use
> trylock and come back later to the mesh which was already locked.
>
> Regards
>
> Dženan Zukić, PhD, Senior R&D Engineer, Kitware (Carrboro, N.C.)
>
> On Thu, Jun 22, 2017 at 3:45 PM, Milef, Nicholas Boris <milefn at rpi.edu>
> wrote:
>
>> Ok, after talking to Zhaohui and profiling, it appears to be a thread
>> synchronization issue (which is why it only shows up in debug mode).
>>
>> This is the problem:
>> The render thread reads the mesh data. If the transform hasn't been
>> applied, it gets applied.
>> The physics thread writes the mesh data. If the transform hasn't been
>> applied, it gets applied.
>>
>> The problem is that the render thread continually modifies the data as
>> it's reading it. Meanwhile, the physics thread is setting data very quickly
>> (or vice-versa, depending who wins the race condition). We saw earlier that
>> the physics thread was less than 1 FPS, but now the render thread is less
>> than 1 FPS. We don't synchronize between threads (which is another
>> problem), so this is what's causing this.
>>
>> Any ideas on how to proceed?
>> ------------------------------
>> *From:* Imstk-developers [imstk-developers-bounces at imstk.org] on behalf
>> of Dzenan Zukic [dzenan.zukic at kitware.com]
>> *Sent:* Friday, June 09, 2017 11:53 AM
>> *To:* Zhaohui Xia
>>
>> *Cc:* imstk-developers at imstk.org
>> *Subject:* Re: [Imstk-developers] high-speed thread in iMSTK
>>
>> Hi Zhaohui,
>>
>> something like this
>> <https://stackoverflow.com/questions/41264827/setting-optimization-settings-in-visual-studio-through-cmake>
>> should work, you need to modify debug mode instead of release though.
>>
>> Regards
>>
>> Dženan Zukić, PhD, Senior R&D Engineer, Kitware (Carrboro, N.C.)
>>
>> On Fri, Jun 9, 2017 at 11:50 AM, Zhaohui Xia <unihui at gmail.com> wrote:
>>
>>> Hi Dzenan,
>>>
>>>
>>>
>>> Thanks for your advice. We need to set it for all the projects in the
>>> solution, is this correct?
>>>
>>> Can we change it in the .CMakeList file to change the whole settings in
>>> an easy way?
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Zhaohui
>>>
>>> *From:* Dzenan Zukic [mailto:dzenan.zukic at kitware.com]
>>> *Sent:* 2017年6月9日 8:57
>>> *To:* Zhaohui Xia <unihui at gmail.com>
>>> *Cc:* Andinet Enquobahrie <andinet.enqu at kitware.com>;
>>> imstk-developers at imstk.org
>>>
>>> *Subject:* Re: [Imstk-developers] high-speed thread in iMSTK
>>>
>>>
>>>
>>> Hi Zhaohui,
>>>
>>>
>>>
>>> to enable a somewhat higher speed of debug mode, you can manually change
>>> the compiler settings for individual projects, see this
>>> <https://msdn.microsoft.com/en-us/library/8f8h5cxt.aspx> and this
>>> <https://msdn.microsoft.com/en-us/library/k1ack8f1.aspx>. Enabling
>>> optimizations increases difficulty of debugging, so you might enable more
>>> optimizations for the Visual Studio projects you are not trying to debug,
>>> and keep optimization disabled or at a low setting for the ones you are
>>> modifying.
>>>
>>>
>>>
>>> Regards
>>>
>>>
>>> Dženan Zukić, PhD, Senior R&D Engineer, Kitware (Carrboro, N.C.)
>>>
>>>
>>>
>>> On Thu, Jun 8, 2017 at 3:33 PM, Zhaohui Xia <unihui at gmail.com> wrote:
>>>
>>> Hi Andinet,
>>>
>>>
>>>
>>> I am afraid I made a mistake. The device thread is definitely a
>>> high-speed thread. I figure out the issue, because I forget to close
>>> something when I change the code in that thread.
>>>
>>>
>>>
>>> I think there is no performance bottlenecks currently in the main thread
>>> under Release mode (60-70HZ), since the mesh size (1000 vertices) is
>>> not very big now.
>>>
>>> But under Debug mode, the speed is too slow, it is just 0.16HZ for the
>>> same mesh. Do we have any ways to improve it, e.g. changing some settings?
>>> It would be very helpful for work if it can run faster.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Zhaohui
>>>
>>> *From:* Andinet Enquobahrie [mailto:andinet.enqu at kitware.com]
>>> *Sent:* 2017年6月8日 13:29
>>> *To:* Zhaohui Xia <unihui at gmail.com>
>>> *Cc:* imstk-developers at imstk.org
>>> *Subject:* Re: [Imstk-developers] high-speed thread in iMSTK
>>>
>>>
>>>
>>> Zhaohui
>>>
>>>
>>>
>>> Can you profile your code and let us know the key performance
>>> bottlenecks in iMSTK?
>>>
>>>
>>>
>>> This is something Dr. Des is also interested. We will be exploring ways
>>> of accelerating some of the modules.
>>>
>>>
>>>
>>> thanks
>>>
>>> Andinet
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Thu, Jun 8, 2017 at 12:40 PM, Zhaohui Xia <unihui at gmail.com> wrote:
>>>
>>> Hi All,
>>>
>>>
>>>
>>> Do we have a high-speed thread (e.g. 1000HZ) in iMSTK? I tried different
>>> modules e.g VRPNDeviceServer (device) and SceneMange (main thread), but the
>>> maximum frame rates of them are 60-70HZ under Release mode.
>>>
>>> I also tried to set the Loopdelay to 0.001 or smaller (from my
>>> understand, its default value is 0 should have the fastest speed, but it
>>> also 60-70HZ).
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Zhaohui
>>>
>>> ------------------------------------------------------------
>>> -----------------------------------------------
>>>
>>> Zhaohui Xia, Ph.D.
>>> Postdoctoral Research Associate, Center for Modeling, Simulation and
>>> Imaging in Medicine (CeMSIM)
>>> Rensselaer Polytechnic Institute
>>>
>>>
>>> _______________________________________________
>>> Imstk-developers mailing list
>>> Imstk-developers at imstk.org
>>> http://public.kitware.com/mailman/listinfo/imstk-developers
>>>
>>>
>>>
>>>
>>>
>>> --
>>>
>>> Andinet Enquobahrie, Ph.D., MBA
>>> Director of Medical Computing
>>> Kitware, Inc.
>>>
>>> http://www.kitware.com
>>>
>>> (919) 969-6990 x311 <%28919%29%20969-6990%20x311>
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Imstk-developers mailing list
>>> Imstk-developers at imstk.org
>>> http://public.kitware.com/mailman/listinfo/imstk-developers
>>>
>>>
>>>
>>
>>
>
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