Work Unit Size - can I select it?

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Work Unit Size - can I select it?

Postby vince_lewis » Tue Apr 24, 2018 3:45 pm

As I spread the good word, I get more people using it - and the occasional issue/observation.

One of the guys I work with has a laptop at work, and a desktop at home. He has FAH installed on both.
He works on his laptop maybe 2 days a week, and the rest at home.

His issue is that the WUs keep timing out on both, as he is not constantly using both machines. Shame as he gets about 300k points a day on his desktop at home, in theory.

Is there an option to select smaller work units, so that they complete rather than getting returned to the pile? In theory, the smaller the work units the better as more get completed. I realise there is an overhead associated with each work unit, but it does seem that FAH is geared towards regular use of a machine which isn't always the case.

So, my question again - using FAHcontrol, is it possible to select a maximum length of work unit, to reduce wastage?

Thanks,
Vince
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Re: Work Unit Size - can I select it?

Postby relbourn » Tue Apr 24, 2018 3:59 pm

Seconded. If you have just the "big guns" you become extremely dependent upon them, especially if you optimise towards them. However if this grows as you want it to (exponentially) then without being dependent on many larger "cpu farms" you could see more return from the smaller folk, because there are more of them. Maybe you can get feedback on the # packets that are not being completed by the smaller computers....?
This is just by decreasing overall job size.
If you make it optional then the user often knows how much they will be using their pc/laptop and can select sizes to suite, that would be fully flexible, depending on the overhead of the code...
However if the code is a few megs anyway, then thats not that much overhead is it? not these days anyway...
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Re: Work Unit Size - can I select it?

Postby Joe_H » Tue Apr 24, 2018 5:20 pm

Yes, you can set a max WU size in FAHControl. However it may not help the way you want. What it is based on is the upload size of the completed WU, the default value of Normal is currently considered to be 25 MB. That also depends on the proper settings being made on the servers, and does not necessarily correspond to how long a WU will take to process.

Code to limit assignments by length of time needed to be processed could be done in theory. But it would require keeping a large database of CPU and GPU related information to determine whether a WU could be completed by a particular machine requesting a WU, and in whatever time period is specified. With limited resources for programming such a new, complicated feature I doubt it would be added to the client.

An option has been provided for small WU's that can be completed quickly. That is by using the NaCl folding client for Chrome. Typically a WU for that client takes less than 30 minutes to complete.
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Re: Work Unit Size - can I select it?

Postby vince_lewis » Tue Apr 24, 2018 5:56 pm

Okay, I understand your point. I can tinker with that, no problem.

That said, is there a case for a wider discussion on either making the work units smaller in general - so we throughout more units but smaller ones, and get fewer returned work units - or perhaps uploading partially completed work units rather than wasting the time that was spent?

I apologise if this has been asked many times before and already answered. My interest is purely in trying to maximise throughput for lower powered or less frequently used cores
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Re: Work Unit Size - can I select it?

Postby bruce » Wed Apr 25, 2018 4:07 am

Take a look at http://fah-web.stanford.edu/new/psummary.html. WUs do have deadlines but WUs are a number of days based on the slowest CPU or the slowest GPU that might be assigned that project. The "big guns" you talk about are many, many times faster that slowest supported hardware, and they often complete those same WUs in a matter of hours. Unfortunately for those systems, there's a lot of overhead downloading/uploading/plus the time it takes the server to construct a Gen (N+1) WU from the Gen N WU that was just returned.

As Joe suggested, the Chrome client (and the CellPhone client) are designed to provide short WUs in spite of the inefficiency I'm talking about.

It would be possible to create WUs that are, say 10% of the length of current WUs (with correspondingly shortened deadlines) and to set up tools to select those projects and a methodology that prevents them from brinh run on "big gun" machines. Unfortunately that would be a major development project that would have to compete for FAH's limited development resources. The first question that would be asked is how much it INCREASES FAH's production but the answer would be "It doesn't" so it would automatically be disqualified from the list of desirable development projects. Then, too, we'd have to find researchers who are comfortable intentionally creating projects that run slower.

Bottom line: Use Chrome.
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Re: Work Unit Size - can I select it?

Postby vince_lewis » Wed Apr 25, 2018 7:31 am

Thanks to both Joe and Bruce for speedy replies.
For anyone else reading this thread, I've added the flag max-packet-size with the value small to the CPU core options via FAHcontrol and I'm going to give that a bash.
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Re: Work Unit Size - can I select it?

Postby bruce » Wed Apr 25, 2018 7:37 am

The max-packet-size flag accepts numbers as well as words.

The setting was designed to accommodate low-speed modems, which (for the most part) no long exist. Early clients did a poor job of working on one WU when another one was uploading or downloading and large data transfers would suspend the FAHCore for significant amounts of time.
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