1) anything that slows down disk access speed can affect run time. Virus
programs might be checking new files created by E+ and slowing things down. I
have bigger problems when the drives get fragmented.
2) If you have multiple cores and/or multiple processors you can see
how they are loaded on an individual basis in the Task Manager’s performance
tab. The E+ executable tends to take an entire core/processor and keep it until
it is done. The Operating System covers up the hardware differences between multiple
processors and multiple cores as far as E+ is concerned, but there will be
memory and disk access speed differences. We routinely use dual, quad core
workstations that can run 8 instances of E+ at the same time.
3) Again the task manager can report out how much memory E+ is using during
a run. Additional memory, up to about 2 gigs, is very helpful. I would
recommend at least 1 gig RAM per core/processor.
From:
Sent: Friday, August 22, 2008
10:41 AM
To:
Subject: [EnergyPlus_Support] Re:
E+ runtime speed
Whoa!
Thanks for the detailed response!
Here are a few additional questions / clarifications:
- I'll try running E+ w/ virus protection shut off
(and PC off the Web). I wasn't aware that McAfee or its ilk would slow
down this type of process.
- I am told by Dell that "Core Duo" and
"Core Quad" PCs are single processor machines with
multiple cores (whatever that means). I'm not sure if that makes a
difference to E+; how can I tell?
- Do we know how much memory is required to hold
the entire program? and whether additional memory helps (much)?
- Since I already have plans to automate the
graphing of output data (numbers alone are SO cumbersome to analyze), do
you care to share any details re: how you did that and what difficulties
or pitfalls you ran into?
Thanks!
--- In
>
> If you are going to do a complex building, expect to wait for answers. And
completely forget about other interesting software like CFD. My last E+ project
with 28 zones took a couple of hours to run. I'm using purchased air and not a
full HVAC system, but I have a lot surfaces and non-rectangular spaces. I
routinely run a few days simulation time to check for errors and then batch
several full runs to work over night...while I sleep...(3 year old 3.4 gig p4,
3 gig 800 meghz memory, raid 0 disk array)...I like sleeping so much I wrote
some utilities to parse and graph my result files automatically after the E+
runs. Nothing like fresh coffee and comparison graphs with breakfast.
>
> Faster processor good - new machines are not pushing the processor speed
in favor of overall operational system performance. Now a clean machine with
minimal overhead extras will be faster.
> Core Duo or Core Quad - E+ does not directly use multiple processors.
However, these processors often have larger internal memory caches, so
performance is improved when only one processor works with the whole cache.
Multiple processors should help if you run something else like a word processor
or Excel while you are waiting, which leads to don't run a bunch of stuff in
the background while you are calculating.
> Big, on chip internal memory cache very good, less time spent waiting for
slower external memory. When I built my computer, I had to trade away the cost
of large internal cache.
> More memory good to a point, you only need enough memory to hold the
entire program without using disk access virtual memory. Fastest front side
memory bus with matched memory is good.
> E+ does spend a lot of time writing files so fast drives, perhaps striped,
and large drive buffers probably helps a bit. Now if you are tapping virtual memory
at all for some reason, run virtual memory on a different fast disk drive
dedicated to only virtual memory. A different volume on the same hard drive
doesn't do the trick.
>
> Time is money, work smarter, it often beats faster, more expensive mistakes...
>
> Ned Lyon, P.E. (MA)
> Staff Consultant
> SIMPSON GUMPERTZ & HEGER
> 781.907.9000 main
> 781.907.9350 direct
> 781.907.9009 fax
> www.sgh.com
>
> From:
> Sent: Thursday, August 21, 2008 4:58 PM
> To:
> Subject: [EnergyPlus_
>
>
> Dear E+ Support,
>
> May I have an update on this post?
>
> In summary, this old post says that:
>
> * Higher processor speed is good
> * More memory helps
> * Multiple processors do not help (e.g., "Core Duo" or Core
Quad")
>
> 1. Does more cache memory help?
> 2. Does the operating system (especially Windows XP vs.
> 3. If 2GB memory is good, is 4GB twice as good?
> 4. Same question for processor speed.
> I am now using a 1.7GHz Core Duo PC with 2GB of RAM. Time is money, and
8-10 minutes seems too long to wait for 20 zones and a full weather year, so
I'm evaluating options.
>
> Thanks in advance!
>
> p.s., The advantage of being impatient is that I've learned numerous ways
to speed things up on my "too slow" PC from this forum that I would
otherwise not know about.
>
>
> --- In
> >
> > For simple buildings, EnergyPlus can be quite fast. However, there
> > are a few hints to help the runtimes.
> >
> > 1. Plain and simple, get the most memory into your computer that you
> > can. We have one file that is a 4 zone building and reports many
> > variables. On a 1.8GHZ computer with 768MB memory, it was running
> > about 8 minutes for a full annual run. On my newer 2.1 GHZ computer
> > with 2G of memory it is about 2 minutes.
> >
> > 2. We continually try to hack away at the run times. Some
> > developers are more atuned to reducing runtimes than others.
> >
> > 3. There are some other hints to try to use: Report on only the
> > variables you need and report on them at hourly or less
> > resolution. Use a lower time step frequency (i.e. 4 rather than 6
> > times per hour).
> >
> > 4. "Does E+ have a "shoebox mode" where is lumps every
thing into a
> > simplified building? I know it has an option to lump windows, but
from what
> > I've seen this is not enough." Not really -- however, if
shadowing
> > is not that important, you can use the "minimal shadowing"
option on
> > the BUILDING object. I am not sure how much that helps.
> >
> > Manually, you can lump like orientation and construction walls into
> > one giant wall -- but this takes considerable work. As you noted you
> > can put multipliers on windows (and in V1.4 doors).
> >
> > 5. "I noticed that Running without HVAC was MUCH faster. What
are best
> > settings to speed up the HVAC code?" Also, you could try the
> > purchased air solution for HVAC -- that should be much faster than
> > other HVAC modes. If you are comparing multiple buildings, the
> > decrease in accuracy of the results may not be as important as
> > getting them running quickly. We also have the System Convergence
> > Limits object -- that can be used to try to fine tune the HVAC
results.
> >
> > 6. "If I get a new 4 processor computer, is E+ written to
efficiency
> > take advantage of multiple processors? Are there any
benchmarks?"
> >
> > We do not use options in the complier to try to make use of multiple
> > processors, as many people will not have that kind of
> > architecture. Getting the most memory you can on the computer does
> > seem to help, as noted above.
> >
> > 7. For a simple building, 50 minutes sounds way too long -- unless
> > your computer is fairly old. How many zones is it? If you would
> > like us to look at it, please upload or send directly.
> >
> >
> > Linda
> >
> > EnergyPlus WebSite: http://www.energypl
> > Owner: EnergyPlus_Support list
> > Member: EnergyPlus Development Team
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
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