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bscheuring1-Visitor
1-Visitor
June 29, 2015
Solved

Slow Mechanism Analysis

  • June 29, 2015
  • 4 replies
  • 7044 views

I have been running a fair amount of analyses in Mechanism lately and the average time it takes to run these ranges anywhere from 1.5 to as long as 6 hours. What I don't understand is my CPU usage rarely goes above 15% and I have plenty of RAM (32gb) to spare.  Are there any config options to make this process a little less painful in terms of run times?  Do I need to upgrade my PC?  What are the usual bottlenecks when running analyses in Mechanism?


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Best answer by danderson

Brian,

Take a closer look at your components and assembly setup.

Are all component placement constraints defined, No assumed references or orientations? (3 placement constraints along with orientation constraints all defined)
What analysis features do you have included in the part files or assembly file? (are you using them to roll up weight, etc)

Are there any part files that take a long time to regenerate? (depending on analysis you are running the part may regenerate once for each step in the mechanism analysis)

What external references do the parts or assembly have? (example "copy geom" or  selected edge, this may contribute to parts regenerating one or more times for each step in the mechanism analysis)

The faster the assembly regenerates normally the faster the mechanism analysis will run and post process the graphs.

Hope this helps,
Don Anderson

4 replies

J
JonathanHodgson13-Aquamarine
13-Aquamarine
June 29, 2015

Hi Brian,

I'm not familiar with Mechanism, but from my experience using Mechanica I'd suggest that it's busy writing and reading data to and from disk (or network).

If you open up Resource Monitor from Task Manager, are your disks seeing a lot of usage (or is the HDD light on the computer constantly on or flickering)?  Or is the network tab in Task Manager showing constant traffic?

Does Mechanism have any settings for temporary data file locations?

An alternative possibility is that Mechanism is a single-thread process and you have a six-core CPU... exactly what CPU do you have (the full description from My Computer, or Control Panel -> System)?

D
DavorGranic16-Pearl
16-Pearl
June 30, 2015

Hi Brian,

Im doing fair amount of mechanisms myself but my analysis times were never that high(15min max).

Using lot of cams and smaller time increments usually slow analysis down.

Can you give us example of what your mechanisms look like? But im guessing problem is completly unrelated to design.

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bscheuring1-VisitorAuthor
1-Visitor
June 30, 2015

Thanks for your replies!!!

My computer specs are as follows:

Processor: Intel(R) Core (TM) i7-4700MQ CPU @ 2.40GHz 2.40 GHz

RAM: 32GB

System type: 64-bit

My PC where I work is pretty much on lock down and I can't view the Resource Monitor without admin rights so I won't be able to view the usage as asked.  It's a little ridiculous I know.

All the models are stored locally on my HDD.

As for the temp files, I'm not sure if Mechanism uses anything separate from the other temp files stored.

Here is the assembly I am working with.  I have the assembly powered with a servo motor on the hydraulic cylinder in the lower left corner of the pic.  Basically this assembly closes inwards on top of itself. 

sample.PNG

J
JonathanHodgson13-Aquamarine
13-Aquamarine
June 30, 2015

OK, the i7-4700MQ is a pretty fast CPU which pretends to have 8 cores (I assume you haven't disabled hyperthreading) - in fact, 15% may well be 12.5% (1 core flat out) plus a percent or two of system overhead.  Unless someone else knows otherwise, it's probably a safe guess that Mechanism will only use one core.

I've had a quick look in Mechanism and can't see any evidence of temp files either, so I think the next point of suspicion is that something in your model or analysis settings is causing very slow convergence - over to the Mechanism experts!

If all my assumptions / guesses above are correct, then there's little point in upgrading your system at least - the best you could get would be about a 20% reduction in run time (by moving to a desktop with one of the fastest Xeons or i7s), whereas fixing the convergence should give a much greater improvement.

B
bscheuring1-VisitorAuthor
1-Visitor
June 30, 2015

Here's a shot of the Task Manager during analysis.

taskmanager.PNG

J
JonathanHodgson13-Aquamarine
13-Aquamarine
June 30, 2015

Eight cores showing, so it does seem very likely that it's one core running flat-out.  Personally I prefer the other view, One Graph All CPUs - there you should see a nice flat line showing the total processor load, rather than watching how Windows spreads the load among the cores (which I really couldn't care less about - although I notice that it's only loading four of the cores, not sharing the load onto the 'virtual' ones).

I also enable Show Kernel Times, which (as I understand it) will at least give some indication of when the CPU is occupied with disk access and other 'low-level' activity.

B
bscheuring1-VisitorAuthor
1-Visitor
June 30, 2015

Kind of like this....

tm2.PNG

    D
    danderson1-VisitorAnswer
    1-Visitor
    July 2, 2015

    Brian,

    Take a closer look at your components and assembly setup.

    Are all component placement constraints defined, No assumed references or orientations? (3 placement constraints along with orientation constraints all defined)
    What analysis features do you have included in the part files or assembly file? (are you using them to roll up weight, etc)

    Are there any part files that take a long time to regenerate? (depending on analysis you are running the part may regenerate once for each step in the mechanism analysis)

    What external references do the parts or assembly have? (example "copy geom" or  selected edge, this may contribute to parts regenerating one or more times for each step in the mechanism analysis)

    The faster the assembly regenerates normally the faster the mechanism analysis will run and post process the graphs.

    Hope this helps,
    Don Anderson

      B
      bscheuring1-VisitorAuthor
      1-Visitor
      July 8, 2015

      When I have more time to elaborate on the problem I found I will however I reduced the run time down to about 2 mins.

      Thanks for the help Don!!!

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