Vensim Performance - Hardware

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goldflo
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Joined: Wed Feb 22, 2017 10:01 am
Vensim version: DSS

Vensim Performance - Hardware

Post by goldflo »

I'm currently working on a very comprehensive Vensim model and each simulation takes about 15 minutes.
That's way too long to be able to work sophistically with Vensim.

What can I do to make Vensim faster without changing the model?
What is the optimal hardware configuration to get the most out of Vensim in terms of speed?
How many cores can be addressed by Vensim? Is there a chance to address more than one?
Administrator
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Joined: Wed Mar 05, 2003 3:10 am

Re: Vensim Performance - Hardware

Post by Administrator »

goldflo wrote:What is the optimal hardware configuration to get the most out of Vensim in terms of speed?
Processor speed is the main one. And a solid state hard drive helps when saving the results.
goldflo wrote:How many cores can be addressed by Vensim? Is there a chance to address more than one?
Just one. Think about the calculation sequence logically, to calculate "A" you need "B" and "C". You could calculate "B" and "C" on separate cores, but you would need to continually check to see if "B" and "C" have been calculated before calculating "A". This is a far larger overhead than just calculating "B" and "C" in sequence.

The following site explains things well, search the text for "To really take advantage of a multi-core system"
https://scalibq.wordpress.com/2012/06/0 ... threading/
goldflo wrote:What can I do to make Vensim faster without changing the model?
There are a number of things.

1. Are you compiling your model? This can lead to a large improvement in run time.
2. Model optimization. This comes only with "experience". For example, if you are calculating a proportion, it's very common practice to do something like
proportion[range] = some value[range] / sum ( some value[range!] )
If "range" has 100 elements, this means you are doing 100 sums every time step. Over the course of a simulation, you could be doing thousands more calculations than you actually need. It's much more efficient to do
total of some value = sum ( some value[range!] )
proportion[range] = some value[range] / total of some value

This goes for VMAX, VMIN and SUM. Take the vector operation out of the equation and you drastically reduce the amount of calculations needed
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391

Units are important!
http://www.bbc.co.uk/news/magazine-27509559
tomfid
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Re: Vensim Performance - Hardware

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