[Opensim-dev] Open Simulator Metrics Reporting Changes (Phase 1) (UNCLASSIFIED)

Fri Apr 17 21:57:48 UTC 2015

+1 on straightening the metrics reported, as long Dahlia's remarks about 
time dilation are cleared out. MisterBlue should chime in too.


On 4/17/2015 8:28 AM, Maxwell, Douglas CIV USARMY ARL (US) wrote:
> Classification: UNCLASSIFIED
> Caveats: NONE
>
> Good Morning Everyone, I'd like to share with you a synopsis of a report
> prepared for me by Steven Zielinski and Sean Mondesire.  This is the result
> of the discussions held with the dev list last month regarding frame rate
> and sampling.  We are preparing to release a number of patches to the open
> simulator developers that will fix a number of inaccurate simulator
> statistics and data collection mechanisms we uncovered while profiling the
> code.  These changes are critical to the correct sampling of the simulator's
> behavior and will affect future development as we introduce new scaling
> (think DSG-after-next) and fidelity enhancements.
>
> The code fixes have been rolled into the MOSES and testing has been positive
> thus far.  Below is a brief discussion of each of the updates for your
> consideration and preparation for the coming patches.  Your constructive
> feedback is welcome.
>
> Sim FPS:
> Previous Metric/Definition:  This was the amount of frames being processed
> during a single second multiplied by a correction factor to make it look as
> though they were processing close to 60 frames per second.
>
> New Metric/Definition:  This is the amount of frames being processed during
> a single second. This is calculated by adding a single frame to a counter
> inside the StatsReporter, and then dividing by the time between statistics
> heartbeats.
>
> Physics FPS:
> Previous:  This was originally handled by the individual physics engines.
> There was a need for a change because there was no threading off of the
> physics engine. Each time the physics engine was updated the program would
> pause and wait for the calculations to complete. Looking into Bullet's
> calculation we found that there was an algorithm numSubSteps *
> m_fixedTimeStep * 1000 * NominalFrameRate. When looking at this further it
> was determined that numSubSteps was the minFrameTime / m_fixedTimeStep. Thus
> the above math becomes minFrameTime * 1000 * NominalFrameRate. This was then
> added to the SimStatsReporter where they divide by 1000. Which left us with
> minFrameTime * NominalFrameRate. This meant that every run through the
> update loop add .089 * 55 to the physics time value of SimStatsReporter.
> This equaled 4.895 so the number of frames times 4.895 resulted in the
> physics FPS for bullet.
>
> New:  This is now the amount of frames being processed during a single
> second. This is calculated by adding a single frame to a counter inside the
> StatsReporter, and then dividing by the time between statistics heartbeats.
> This matches the Sim FPS because they are currently running on the same
> thread and only a single frame of physics is updated when a single frame of
> the simulation is updated.
>
> Total Frame Time:
> Previous:  Here we needed to add a stopwatch instead of using the original
> EnvironmentTickCount. The reason for the change was that the
> EnvironmentTickCount only updates a few times a second while the stopwatch
> will get an exact time in milliseconds. This change was also done for the
> physics and simulation time. Also this used to only grab a single frame
> (including the sleep and statistics gathering) and display the result.  The
> single frame was changed on both the physics and simulation time as well.
>
> New:  This is now an average for the past N frames of the total time it took
> to complete a frame. Where N is the value given inside of the OpenSim.ini
> file by the variable NumberOfFrames inside of the Statistics section. This
> includes the time that opensim slept to match the current frame time.
>
> Physics Time:
> Previous:  Only had the changes listed in total frame time.
>
> New:  This is now an average for the past N frames of the total time it took
> to complete a physics update to the scene. Where N is the value given inside
> of the OpenSim.ini file by the variable NumberOfFrames inside of the
> Statistics section. This includes the time that opensim ran the
> preprocessing of physics and the physics update. If physics is disabled the
> time it took to check whether physics was disabled is used.
>
> Simulation Time:
> Previous: Changed the things listed in total frame time. Also changed that
> instead of calculating each section (tempOnRezMS, eventMS, backupMS,
> terrainMS, landMS) there were only two sections. The reason for two
> sections, the physics section separates parts of the simulation section.
> Each section that was originally included has remained the same.
>
> New:  This is now an average for the past N frames of the total time it took
> for the simulation to run. Where N is the value given inside of the
> OpenSim.ini file by the variable NumberOfFrames inside of the Statistics
> section. This does not include the time that physics was running or the time
> that open sim slept to match the current frame time.
>
> Time Dilation:
> Previous:  Originally just returned the PhysicsScene value for TimeDilation
> which is 1.0.
>
> New:  The time it took for the physics and simulation to run not including
> the sleep time, divided by the minFrameTime passed into the program from the
> OpenSimDefaults.ini file variable MinFrameTime. This would mean that a value
> of 1 is no sleep necessary, less than 1 and the program slept for some
> remaining amount of time, and greater than 1 the physics and simulation took
> longer to run than the allotted time.
> ((simulationFrameTime+physicsFrameTime)/minFrameTime)  All times are based
> on a single frame and not averaged across multiple data points.
>
>
> v/r -doug
>   
> Douglas Maxwell, MSME
> Science and Technology Manager
> Virtual World Strategic Applications
> U.S. Army Research Lab
> Simulation & Training Technology Center (STTC)
> (c) (407) 242-0209
>
>
>
>
> Classification: UNCLASSIFIED
> Caveats: NONE
>
>
>
>
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