Search found 2764 matches

by tomfid
Wed Nov 13, 2019 10:06 pm
Forum: Vensim
Topic: Vensim flicks and flips off completely sometimes
Replies: 8
Views: 43

Re: Vensim flicks and flips off completely sometimes

Does this happen when you are editing the diagram - adding arrows, moving variables, etc. - or when you're in the equation editor?
by tomfid
Wed Nov 13, 2019 8:46 pm
Forum: Vensim
Topic: Documentation for Delay Information gives false examples
Replies: 5
Views: 15

Re: Documentation for Delay Information gives false examples

In Ventity, the equivalent function has access to the full time series history of the input, and therefore when the delay changes, it simply (instantaneously) shifts the lookup to a different point. I think the key question here is, what real-world phenomenon are we trying to represent? The Ventity ...
by tomfid
Wed Nov 13, 2019 8:21 pm
Forum: Vensim
Topic: Documentation for Delay Information gives false examples
Replies: 5
Views: 15

Re: Documentation for Delay Information gives false examples

gwr wrote:
Wed Nov 13, 2019 8:00 pm
Thanks, for acknowledging the false behavior, Tom - not everybody does. ;-)
Hey, no politics in the forum! ;-)
by tomfid
Wed Nov 13, 2019 8:19 pm
Forum: Vensim
Topic: Precision
Replies: 3
Views: 14

Re: Precision

It seems unlikely that the difference is numerics, unless the model is chaotic, or at least dominant positive feedback, and you're running for a long time. The xmile test suite includes a number of models that yield ~identical results in Vensim, ithink and Python (PySD). Python storage is normally g...
by tomfid
Wed Nov 13, 2019 6:42 pm
Forum: Vensim
Topic: Documentation for Delay Information gives false examples
Replies: 5
Views: 15

Re: Documentation for Delay Information gives false examples

I haven't looked at the code yet, but I think there's a method to the madness. The delay is treated like a queue of variable length. When the delay changes duration, it shortens or lengthens the queue, but it doesn't rewrite the existing values. So, values reflecting the new pipeline duration don't ...
by tomfid
Wed Nov 13, 2019 3:09 pm
Forum: Vensim
Topic: Precision
Replies: 3
Views: 14

Re: Precision

There's no simple answer to this question. A single precision float is about 7 decimals, and double precision is 15. (Most Vensim versions are now double precision.) However, the precision of the answer also depends on simulation method and specific equation choices. Fortunately, this rarely matters...
by tomfid
Tue Nov 12, 2019 9:46 pm
Forum: Ventity
Topic: "The configuration is read only" error
Replies: 9
Views: 107

Re: "The configuration is read only" error

Email us at info at ventity.biz and we'll get you fixed up with a new build that may solve the problem.
by tomfid
Thu Nov 07, 2019 3:19 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

Normally the LCOE or similar will determine investment in various sources.

In the short run, the decision to generate or not should be based only on variable costs (fuel, variable O&M).
by tomfid
Thu Nov 07, 2019 3:17 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

The allocation function section of the help explains the algorithm for market clearing. https://www.vensim.com/documentation/fn_allocations.htm Specifically: https://www.vensim.com/documentation/24325.htm On your points: 1) true 2) not strictly required, but should be true if you expect to see suppl...
by tomfid
Wed Nov 06, 2019 6:22 pm
Forum: Ventity
Topic: "The configuration is read only" error
Replies: 9
Views: 107

Re: "The configuration is read only" error

OK ... another possibility is that the model is loading read-only. What happens if you move the sample model to another place - maybe your Documents folder? Or, what if you create/run a new, empty model in a location where you're sure you have permissions? (Sorry for snatching at straws here - these...
by tomfid
Wed Nov 06, 2019 4:10 pm
Forum: Vensim
Topic: Vensim 8 without single precision?
Replies: 6
Views: 38

Re: Vensim 8 without single precision?

Also, the memory limit is only significant for very large models, and that's now relieved by the availability of 64-bit Vensim, which can access memory far exceeding what's practical to run.
by tomfid
Wed Nov 06, 2019 4:06 pm
Forum: Vensim
Topic: 'Find' command
Replies: 4
Views: 29

Re: 'Find' command

Also, rather than:

GET XLS( 'mydata.xlsx', ... )

you can use

GET XLS( '?my data', ... )

when Vensim encounters the ? it will query for the data file location, and store it for future use. Thereafter, you can manage the data pointer via Model>Settings>XLS Files.
by tomfid
Wed Nov 06, 2019 4:02 pm
Forum: Vensim
Topic: 'Find' command
Replies: 4
Views: 29

Re: 'Find' command

Notepad++ definitely should have worked - I use it all the time.

Another option is to do this in the text editor (View>As Text) and use the Replace or Replace String command.
by tomfid
Wed Nov 06, 2019 1:41 am
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

Yes - I think the problem is priorities that don't overlap. Demand has priority 0.1 with width .001, and all the supplies are at ~125 with width 1e-6. That yields a nonoverlapping set - there is no price at which demanders and suppliers want nonzero throughput.
by tomfid
Wed Nov 06, 2019 1:37 am
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

Ah ... I should have seen this before. You're using the "Estimated Energy Price" in the Amount Supplied and Amount Demanded. But for the SUPPLY and DEMAND functions to work, they need the market clearing priority as input. Fixing that reconciles the input/output discrepancy, but there's still someth...
by tomfid
Wed Nov 06, 2019 1:28 am
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

I see what you mean - investigating.
by tomfid
Tue Nov 05, 2019 3:50 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 34
Views: 1198

Re: sensitivity analysis (vensim)

Can you increase the SAVEPER or thin out the savelist a bit? If you're getting gigabytes of output from a one or two simulations, it'll be pretty unwieldy when there are many.
by tomfid
Tue Nov 05, 2019 3:18 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

We'll need the data file to run it.
by tomfid
Tue Nov 05, 2019 3:15 pm
Forum: Ventity
Topic: "The configuration is read only" error
Replies: 9
Views: 107

Re: "The configuration is read only" error

The problem is typically with %appdata%/Local/VentityConfig.xml.

I'll check with the programming team for other ideas.
by tomfid
Mon Nov 04, 2019 9:53 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

What is the problem symptom?
by tomfid
Mon Nov 04, 2019 3:13 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

Or email us.

What are the symptoms of not working quite right? This has been tested and used extensively, so a bug is possible but unlikely.
by tomfid
Sun Nov 03, 2019 4:32 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

You might compare your version to the sample model in the Help system.

I think we can't diagnose this without more information - a model, or at least the relevant subscripts and related equations.
by tomfid
Tue Oct 29, 2019 9:31 pm
Forum: Vensim
Topic: Allocation by Priority and Demand Values
Replies: 20
Views: 194

Re: Allocation by Priority and Demand Values

OK, nice work!
by tomfid
Tue Oct 29, 2019 8:41 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 34
Views: 1198

Re: sensitivity analysis (vensim)

Actually, I see that the error happens on sim 1. Looking at the code, the counter for writing sensitivity result blocks is an integer, which will impose a 2 gigabyte limit per simulation. Any chance you're near that?
by tomfid
Tue Oct 29, 2019 7:09 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 34
Views: 1198

Re: sensitivity analysis (vensim)

Are you using 32 or 64 bit Vensim? If you do a run with only 1 sensitivity instance (if you can), how big is the file size increment over a non-sensitivity vdf file?