Re: [EnergyPlus_Support] E+ runtime speed

[Linda Lawrie <linda@xxxxxxxxxx>]

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.energyplus.gov
Owner: EnergyPlus_Support list
Member: EnergyPlus Development Team



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