Search found 3808 matches

by tomfid
Fri Aug 07, 2015 5:48 pm
Forum: Vensim
Topic: Deleting shadow variables
Replies: 3
Views: 2766

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: 6330

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: 5320

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: 5320

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...
by tomfid
Thu Aug 06, 2015 12:49 am
Forum: Vensim
Topic: Migrating values w/in an array (or to another if necessary!)
Replies: 9
Views: 5320

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

OK, I think I get it. It seems like an inevitable consequence is that if any subarea has >20 objects, you have a problem fitting them all in with the offsets? With that restriction, I think there's a simple solution. Do you need to pack the vector to get rid of 0s, i.e. 3,17,21,0,19 -> 3,17,21,19 ?
by tomfid
Wed Aug 05, 2015 10:01 pm
Forum: Vensim
Topic: Migrating values w/in an array (or to another if necessary!)
Replies: 9
Views: 5320

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

Also ... not sure I follow the problem statement. If each of 3 subareas contains up to 60 objects, wouldn't you need a vector of up to 180 elements to store the consolidated positions?
by tomfid
Wed Aug 05, 2015 9:58 pm
Forum: Vensim
Topic: Migrating values w/in an array (or to another if necessary!)
Replies: 9
Views: 5320

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

How many objects and areas will there be eventually? It might be easier to just use brute force and track every object/area location, rather than trying to reuse IDs.
by tomfid
Wed Aug 05, 2015 9:55 pm
Forum: Vensim
Topic: Deleting shadow variables
Replies: 3
Views: 2766

Re: Deleting shadow variables

That's odd ... Delete -> Remove from this view but do not change model structure is what you should be using. I do it all the time. Can you post/send a model saved before/after such an operation? What OS are you on?
by tomfid
Wed Aug 05, 2015 3:51 pm
Forum: Ventity
Topic: Updated build 457
Replies: 2
Views: 3259

Re: Updated build 457

Great. I'm sure we'll have more teething problems, but it's good to have the basics working!
by tomfid
Wed Aug 05, 2015 3:50 pm
Forum: Vensim
Topic: floating point issues and warnings
Replies: 2
Views: 1738

Re: floating point issues and warnings

I think the problem is that your adoption from advertising is too high. You have: adoption from advertising 0 = "effectiveness of advertising & promotion"*potential users 0*marketing investment So "effectiveness of advertising & promotion"*marketing investment is effectiv...
by tomfid
Tue Aug 04, 2015 8:28 pm
Forum: Ventity
Topic: Updated build 457
Replies: 2
Views: 3259

Updated build 457

There's a new build 457 that fixes the help system issues, plus some bug fixes and feature upgrades. Get it at http://vensim.com/ventity.html
by tomfid
Tue Aug 04, 2015 8:24 pm
Forum: Ventity
Topic: Possible performance issue with Windows Update
Replies: 4
Views: 7190

Re: Possible performance issue with Windows Update

We found it on Windows 8.1. It went away after I rolled back updates to about June 15. The problem is, the update process queues changes that don't take effect until a reboot, which makes it very tough to determine which KB item is the culprit. No one has seen the problem on Win7, and no one has tri...
by tomfid
Tue Aug 04, 2015 4:45 pm
Forum: Vensim
Topic: FIND ZERO convergence issues with subscripts
Replies: 4
Views: 4749

Re: FIND ZERO convergence issues with subscripts

It seems like there ought to be an analytic solution, but I don't know it off the top of my head. You can separate the processing of the FIND ZERO subscripts by writing the equation to solve one element at a time (as in IRRGCC), but that would be a pain. A better approach, I think, is to detect the ...
by tomfid
Tue Aug 04, 2015 4:18 pm
Forum: Vensim
Topic: How do i factor in efficiency losses in a model?
Replies: 2
Views: 1819

Re: How do i factor in efficiency losses in a model?

MODEL 1 b.mdl model 2 b.mdl In model 2, you're missing the outflow of process losses, so the losses "pile up" in the stock of WIP. I've modified to rectify that. In both models, there's an unaddressed question of whether managers know about the losses and adjust production to offset them....
by tomfid
Tue Aug 04, 2015 3:51 pm
Forum: Vensim
Topic: FIND ZERO convergence issues with subscripts
Replies: 4
Views: 4749

Re: FIND ZERO convergence issues with subscripts

Is there a reason for not using the INTERNAL RATE OF RETURN function here?
by tomfid
Sat Aug 01, 2015 2:18 pm
Forum: Vensim
Topic: Simulating specific subscripts
Replies: 3
Views: 2459

Re: Simulating specific subscripts

However, there is no way to selectively turn off a set of subscripts at runtime without changing model structure. Why do you need this? Maybe there's another way.
by tomfid
Tue Jul 28, 2015 12:51 pm
Forum: Ventity
Topic: Installation Problems
Replies: 5
Views: 5655

Re: Installation Problems

We haven't posted it widely yet, but I'll PM it to you. You should have received a link in an email from ventity.biz - I'll check to be sure you're on the list.
by tomfid
Sat Jul 25, 2015 7:21 pm
Forum: Ventity
Topic: Installation Problems
Replies: 5
Views: 5655

Re: Installation Problems

We'll fix the paths and release a new build as soon as everyone's back from the conference.
by tomfid
Sat Jul 25, 2015 1:20 am
Forum: Vensim
Topic: Problems with "Find zero" convergence
Replies: 13
Views: 6167

Re: Problems with "Find zero" convergence

FIND ZERO dispatch.mdl The above setup might work. It needs demand/supply curves and parameters, but hopefully you can guess the intent from the units & names. The purpose of the "unserved" item is to permit convergence even in extreme conditions (low supply and inelastic high demand)...
by tomfid
Sat Jul 25, 2015 12:12 am
Forum: Vensim
Topic: Problems with "Find zero" convergence
Replies: 13
Views: 6167

Re: Problems with "Find zero" convergence

I think the issue is that Difference Quantity isn't a vector. The first four arguments all need to have the same dimension. It should be possible to reformulate this problem to work, perhaps by computing a single shadow price and deriving exports from that. I'll have to think about it.
by tomfid
Fri Jul 24, 2015 11:38 pm
Forum: Ventity
Topic: ventity.exe does not work
Replies: 4
Views: 4986

Re: ventity.exe does not work

Good that it works. We'll get a new build with the help link issue resolved as soon as we're back from the SD conference. I'll email an announcement to users and post here.
by tomfid
Thu Jul 23, 2015 2:23 am
Forum: Vensim
Topic: Problems with "Find zero" convergence
Replies: 13
Views: 6167

Re: Problems with "Find zero" convergence

I'm happy to look at it after the SD conference.
by tomfid
Thu Jul 23, 2015 2:06 am
Forum: Ventity
Topic: ventity.exe does not work
Replies: 4
Views: 4986

Re: ventity.exe does not work

My guess is that there is some issue with XP. As far as I know we have only tested on Win7 and Win8/8.1.
by tomfid
Thu Jul 23, 2015 2:05 am
Forum: Vensim
Topic: about Ventity
Replies: 3
Views: 2780

Re: about Ventity

by tomfid
Wed Jul 22, 2015 9:32 pm
Forum: Vensim
Topic: Display subscripts values during synthesim
Replies: 1
Views: 2283

Re: Display subscripts values during synthesim

If you click on the slider arrow, you get a dialog that permits selecting a different element, but there's no way to show all at once. It's a feature we'd like too.