Search found 2888 matches

by tomfid
Sat Apr 04, 2020 6:26 pm
Forum: Vensim
Topic: External function version mismatch
Replies: 12
Views: 76

Re: External function version mismatch

Can the existing setup be preserved via addition of _VDFX to the compiler preprocessor definition list, or are there other things that need to change?

One option would be to do a diff on the new shipping venext.c example vs. your venext.c and see what differs.
by tomfid
Fri Apr 03, 2020 12:29 pm
Forum: Vensim
Topic: External function version mismatch
Replies: 12
Views: 76

Re: External function version mismatch

Right - you need to modify your .dll project to use the new copy of vensim.h etc. (typically in users\public\comp).
by tomfid
Fri Apr 03, 2020 1:06 am
Forum: Vensim
Topic: External function version mismatch
Replies: 12
Views: 76

Re: External function version mismatch

This means you have an external function library loaded that needs to be recompiled with the new version's headers.

If you're not using it, you can delete the reference at Tools>Options>Startup.
by tomfid
Thu Apr 02, 2020 6:20 pm
Forum: Vensim
Topic: Use of MCMC
Replies: 5
Views: 70

Re: Use of MCMC

Will look when I can. Your description sounds right though. Just watch out for missing minus signs - easy mistake to make.
by tomfid
Thu Apr 02, 2020 5:09 pm
Forum: Vensim
Topic: Use of MCMC
Replies: 5
Views: 70

Re: Use of MCMC

Sorry - requires some thought and I've been ultra busy. 1. This is not automated yet, so you have to create an equation to express your prior. Here's an example. Suppose I have a policy effect parameter. If you don't know what its value could be, just that it's >0, you could use the improper log-uni...
by tomfid
Thu Apr 02, 2020 4:41 pm
Forum: Vensim
Topic: Function for reading from a vdf file
Replies: 6
Views: 13

Re: Function for reading from a vdf file

Another trick that I used ages ago, before GET VDF existed, was to create a separate model containing just a pair of variables that transform the base value into a data variable with a different name. Something like: Main model: price of cheese = {some simulated stuff} data price of cheese {data var...
by tomfid
Thu Apr 02, 2020 4:09 pm
Forum: Vensim
Topic: Function for reading from a vdf file
Replies: 6
Views: 13

Re: Function for reading from a vdf file

Great! It's been a while since I've done this, but there's always a chicken-egg problem when the Base run that you're looking up comparison values from doesn't exist yet. I think I've solved this with some kind of IF THEN ELSE( base data = :NA:, 0, base data) logic, but I don't remember the details....
by tomfid
Thu Apr 02, 2020 2:19 pm
Forum: Vensim
Topic: Function for reading from a vdf file
Replies: 6
Views: 13

Re: Function for reading from a vdf file

I think you want GET VDF DATA.
by tomfid
Wed Apr 01, 2020 4:34 pm
Forum: Vensim
Topic: Customized Analysis Toolset
Replies: 3
Views: 31

Re: Customized Analysis Toolset

I agree - this worked until very recently. We'll have a fix soon.
by tomfid
Mon Mar 30, 2020 12:47 pm
Forum: Vensim
Topic: TIME STEP and historical data
Replies: 14
Views: 71

Re: TIME STEP and historical data

If you think about a run with 4 time steps, the random draws might be Time 1 2 3 4 Value 3 8 2 6 If you halve the time step, you get Time 0.5 1 1.5 2 2.5 3 3.5 4 Value 3 8 2 6 1 7 7 9 The value 2 now occurs at time 1.5 instead of time 2, etc. In a real model, it's more complex than that, because you...
by tomfid
Mon Mar 30, 2020 12:31 pm
Forum: Vensim
Topic: TIME STEP and historical data
Replies: 14
Views: 71

Re: TIME STEP and historical data

Time step will have a big effect on any randomness - if you draw twice as many values, you get a completely different realization of the random streams. To calibrate a model with random inputs, you really need to look at the performance over an ensemble of simulations, rather than a single run. This...
by tomfid
Sun Mar 29, 2020 4:09 pm
Forum: Vensim
Topic: TIME STEP and historical data
Replies: 14
Views: 71

Re: TIME STEP and historical data

The best thing to do is create some custom graphs that compare the model to the data, and then do some hand calibration to see what's going on.
by tomfid
Sun Mar 29, 2020 4:08 pm
Forum: Vensim
Topic: TIME STEP and historical data
Replies: 14
Views: 71

Re: TIME STEP and historical data

If shrinking the time step is changing the payoff, that's probably a sign that it's also changing the dynamics, and that in turn is changing the fit.

The choice of time step really shouldn't have anything to do with the data interval.
by tomfid
Sat Mar 28, 2020 10:12 pm
Forum: Vensim
Topic: Vensim DSS Crashes on macOS
Replies: 5
Views: 37

Re: Vensim DSS Crashes on macOS

I think this might be a bug in the payoff reporting that we've fixed in development already. If so, the .out file written should still contain your final parameters, so you can rerun the endpoint solution.
by tomfid
Fri Mar 27, 2020 11:56 pm
Forum: Vensim
Topic: Flow created as constant rather than auxiliary
Replies: 2
Views: 24

Re: Flow created as constant rather than auxiliary

The interface is probably a little confusing on this point. A flow, and auxiliary, and a constant are really the same thing in the language. The defining characteristic is that they use the = assignment operator. If you write = 3, it's a constant, and if you write = 1/x, or = 1/3, or anything else t...
by tomfid
Fri Mar 27, 2020 1:19 pm
Forum: Vensim
Topic: Low optimisation speed
Replies: 9
Views: 56

Re: Low optimisation speed

I don't think the SSD will matter much for optimizations, because it's not writing much data until the end. I didn't notice in your first post that it was a Ryzen 7. This could be an AMD/Intel difference. Historically, AMDs had more cores, but Intels were about twice as fast per core. I thought they...
by tomfid
Fri Mar 27, 2020 3:56 am
Forum: Vensim
Topic: Low optimisation speed
Replies: 9
Views: 56

Re: Low optimisation speed

There shouldn't be much difference from the OS. Any chance you were running compiled on the Mac?
by tomfid
Thu Mar 19, 2020 8:49 pm
Forum: Vensim
Topic: Discret function
Replies: 1
Views: 40

Re: Discret function

Not sure what tapping a furnace really means, but there are at least two options: 1. Create data (excel side) with 0 or 1 at every time step, representing whether tapping is underway, and just read that into a data variable. 2. Create data with 1 only at the times where tapping occurs, then change t...
by tomfid
Thu Mar 12, 2020 6:03 pm
Forum: Vensim
Topic: Thick Lines feature for Graphs not working properly
Replies: 3
Views: 64

Re: Thick Lines feature for Graphs not working properly

If you need thick lines for everything, you can use a Custom Graph.
by tomfid
Thu Mar 12, 2020 6:02 pm
Forum: Vensim
Topic: Thick Lines feature for Graphs not working properly
Replies: 3
Views: 64

Re: Thick Lines feature for Graphs not working properly

This has always been the way it worked. The first run has a one point line, 2nd run is two point, etc. The current release already has new graphics for regular graphs, and the next major release will have new graphics for everything (you can preview in the coronavirus video, https://vensim.com/coron...
by tomfid
Wed Mar 11, 2020 1:18 pm
Forum: Vensim
Topic: Git
Replies: 3
Views: 133

Re: Git

Or update your version - newer ones do this automatically.
by tomfid
Tue Mar 10, 2020 10:49 am
Forum: Vensim
Topic: FREE connection between xls and Vensim
Replies: 3
Views: 103

Re: FREE connection between xls and Vensim

Distributing a packaged model with a redistributor's license is one option. Another might be to use Ventity, which has a low license fee ($100/yr).
by tomfid
Fri Mar 06, 2020 11:25 pm
Forum: Ventity
Topic: New models of possible interest
Replies: 1
Views: 176

New models of possible interest

I've posted a few Ventity models that may be of interest recently:
https://metasd.com/category/model-library/
by tomfid
Fri Mar 06, 2020 11:24 pm
Forum: Ventity
Topic: Ventity Optimization dialog a bit wonky?
Replies: 6
Views: 1057

Re: Ventity Optimization dialog a bit wonky?

There may be a fix in the dev builds - I'll check. Email ventity dot biz if you need access.