Given funding and staff, it would be
technically possible to rewrite E+ for multi-threading. But a better use of tax
dollars seems to be to wait for compilers to get better. I suspect that soon enough
we’ll be able just use advanced compiler features and not have to
re-write much code.
Right now, you can make full use of the extra
cores by running multiple instances of EnergyPlus at same time.
From:
Sent: Thursday, August 21, 2008
9:18 PM
To:
Subject: RE: [EnergyPlus_Support]
Re: E+ runtime speed
Is it technically possible to re-write E+ that would enable it
to do multi-threading, so we can use the extra computing of multi-processors or
multi-cores? Perhaps given the funding? Or the equations and energy
balances behind E+ would not allow such multi-threading?
From:
Sent: Friday, August 22, 2008 6:46
AM
To:
Subject: RE: [EnergyPlus_
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")
- Does more cache memory help?
- Does the operating system (especially Windows XP
vs.
- If 2GB memory is good, is 4GB twice as good?
- 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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