Search found 3804 matches

by tomfid
Tue Sep 22, 2015 4:10 pm
Forum: Ventity
Topic: Possible performance issue with Windows Update
Replies: 4
Views: 6749

Re: Possible performance issue with Windows Update

Win10 does seem to be an improvement all around. I haven't had any issues. The Win8 update issue seems to be resolved as well.
by tomfid
Wed Sep 16, 2015 2:36 pm
Forum: Ventity
Topic: problem in the exercise 6 of the tutorial
Replies: 1
Views: 2780

Re: problem in the exercise 6 of the tutorial

Thanks ... I'll check it out.
by tomfid
Tue Sep 15, 2015 5:11 pm
Forum: Vensim
Topic: traffic modelling (roundabout) distribution
Replies: 1
Views: 1474

Re: traffic modelling (roundabout) distribution

roundabout 1.mdl
(2.26 KiB) Downloaded 191 times
It might be easiest to generate arrivals for each origin-destination pair independently. See attached for an example.
by tomfid
Wed Sep 09, 2015 4:54 am
Forum: Vensim
Topic: Question on GET XLS DATA
Replies: 4
Views: 2757

Re: Question on GET XLS DATA

The data variable won't contain any interpolated or held points, but when it's used, you'll see them downstream.

For example, try:

myData := GET XLS DATA( ... )
myAux = myData

Then play around with the interpolation pattern and take a look at myAux.
by tomfid
Tue Sep 08, 2015 9:46 pm
Forum: Vensim
Topic: Question on GET XLS DATA
Replies: 4
Views: 2757

Re: Question on GET XLS DATA

by tomfid
Tue Sep 08, 2015 9:44 pm
Forum: Vensim
Topic: How to store and retrieve past variable values
Replies: 2
Views: 2032

Re: How to store and retrieve past variable values

You can use the DELAY FIXED function to create a stock representing the 3-year moving accumulation. For example:

profit = ...
cumulative profit = INTEG( adding - removing, 0 )
adding = profit
removing = DELAY FIXED( profit, horizon, 0 )
horizon = 3
average profit = cumulative profit / horizon
by tomfid
Tue Sep 08, 2015 5:09 pm
Forum: Ventity
Topic: Delay and smooth functions in ventity
Replies: 1
Views: 2942

Re: Delay and smooth functions in ventity

We haven't implemented any of the dynamic functions yet - we're waiting on a bit of development for an internal capability something like Vensim MACRO functions. Some of the complex delays, like conveyors, probably won't be implemented, because they can be done better by creating cohorts of entities...
by tomfid
Tue Sep 08, 2015 5:07 pm
Forum: Ventity
Topic: help to understand how Ventity works
Replies: 5
Views: 5190

Re: help to understand how Ventity works

Good idea. We'll see what we can cook up. It may be tricky in some situations, because there are things Ventity does that will be hard to represent in Vensim.
by tomfid
Tue Sep 01, 2015 6:43 pm
Forum: Vensim
Topic: "Nobody ever gets credit" model
Replies: 5
Views: 4655

Re: "Nobody ever gets credit" model

It seems like the paper doesn't fully document the models and experiments, so it's hard to know what's missing.

Fixing units is a good start, but I'd email the authors and see if the model, or at least an equation listing, is available.
by tomfid
Fri Aug 28, 2015 4:01 pm
Forum: Vensim
Topic: Looking for someone with Forio experience
Replies: 1
Views: 2651

Re: Looking for someone with Forio experience

I can ask around. You might also try asking on the SD discussion forum.
by tomfid
Mon Aug 24, 2015 5:42 pm
Forum: Vensim
Topic: Improving iterations!
Replies: 9
Views: 5688

Re: Improving iterations!

It would help to have a description of what you're trying to achieve with this calculation. There might be an easier way.
by tomfid
Mon Aug 24, 2015 5:40 pm
Forum: Vensim
Topic: Improving iterations!
Replies: 9
Views: 5688

Re: Improving iterations!

To use find zero, you'd have to define a one-dimensional array i_j of size ELMCOUNT(i)*ELMCOUNT(j) and map t[i,j] to t2[i_j]. Then you could use the find zero functionality to iterate.

This would probably work better as an external function though.
by tomfid
Mon Aug 24, 2015 3:21 pm
Forum: Vensim
Topic: How can I fix this problem ?
Replies: 12
Views: 5867

Re: How can I fix this problem ?

Here's a double precision .vdf:
double1.vdf
(43.62 KiB) Downloaded 210 times
by tomfid
Fri Aug 21, 2015 2:37 pm
Forum: Vensim
Topic: How can I fix this problem ?
Replies: 12
Views: 5867

Re: How can I fix this problem ?

The only simple, general answer is to switch to a double precision Vensim version. You would have exactly the same problem if you were working in a programming language using floats instead of doubles. But why does this matter in practice? It would be very unusual for a real system to be free of dis...
by tomfid
Thu Aug 20, 2015 4:26 pm
Forum: Vensim
Topic: VECTOR LOOKUP with variable X intervals
Replies: 4
Views: 2834

Re: VECTOR LOOKUP with variable X intervals

It's possible with subscripting. Take a look at this:
var lookup.mdl
(3.96 KiB) Downloaded 206 times
I did this once before, long ago, and the result was more elegant as I recall, so perhaps someone can improve on it.
by tomfid
Thu Aug 20, 2015 4:23 pm
Forum: Vensim
Topic: How can I fix this problem ?
Replies: 12
Views: 5867

Re: How can I fix this problem ?

I don't think there's a way to make the exact technical problem go away in general; I'd have to know something about the specific problem to suggest a practical solution.
by tomfid
Thu Aug 20, 2015 3:22 pm
Forum: Vensim
Topic: How can I fix this problem ?
Replies: 12
Views: 5867

Re: How can I fix this problem ?

This is a limitation of single-precision number representation. In Vensim DSS double precision, the model comes exactly into equilibrium.
by tomfid
Thu Aug 13, 2015 4:24 pm
Forum: Ventity
Topic: Introducing Ventity beta 1
Replies: 2
Views: 4556

Re: Introducing Ventity beta 1

There isn't any document, or interoperability, yet. We will create a translator for Vensim models to Ventity, most likely via XMILE. Simple models and components should translate ~100%. We don't expect full two-way translation of models to be practical. Coming from Vensim, it doesn't make sense to m...
by tomfid
Mon Aug 10, 2015 4:28 pm
Forum: Vensim
Topic: Can´t install the software!
Replies: 1
Views: 1457

Re: Can´t install the software!

I just downloaded, installed and ran PLE 5.11 on a Win8.1 x64 machine, and it worked fine. Perhaps your downloaded file really is corrupted. Try the download again?
by tomfid
Sat Aug 08, 2015 4:35 pm
Forum: System Dynamics Discussion
Topic: arcane arrays
Replies: 9
Views: 9886

Re: arcane arrays

"Arcane" may not be the best word. However, in my experience, there are often a few points in a model, usually where the dimensionality is changing, that do require very complex and opaque subscripting. Now that I've been using Ventity for a little while, I'm also finding it annoying to ha...
by tomfid
Fri Aug 07, 2015 5:48 pm
Forum: Vensim
Topic: Deleting shadow variables
Replies: 3
Views: 2754

Re: Deleting shadow variables

No harm done; seems like a worthy experiment.
by tomfid
Fri Aug 07, 2015 2:02 pm
Forum: Vensim
Topic: Passing a cost at a discrete time to a variable
Replies: 13
Views: 6303

Re: Passing a cost at a discrete time to a variable

Hotel construction 2.mdl Here are two general strategies - changes highlighted. Option A is to charge the construction with the flow when it occurs. Option B is to detect changes in the stock, using DELAY FIXED to keep track of the previous value, and charge accordingly. I think A is the preferred ...
by tomfid
Thu Aug 06, 2015 1:58 pm
Forum: Vensim
Topic: Migrating values w/in an array (or to another if necessary!)
Replies: 9
Views: 5302

Re: Migrating values w/in an array (or to another if necessa

Yes, I think a little more information about the problem statement would help here.
by tomfid
Thu Aug 06, 2015 2:30 am
Forum: Vensim
Topic: Migrating values w/in an array (or to another if necessary!)
Replies: 9
Views: 5302

Re: Migrating values w/in an array (or to another if necessa

Filtering the 0s would be more complicated, but I think it's doable. I can't cook up an answer on the fly though. Here's a stab at the simple way - not sure it's really responsive to your situation, but code is the best way to find out: objects : (o1-o60)~~| objects1 : (o1-o20) -> objects2, objects3...