Search found 3806 matches

by tomfid
Mon Jun 03, 2013 4:19 pm
Forum: Vensim
Topic: Vensim PLE and 64 bit Windows
Replies: 3
Views: 2667

Re: Vensim PLE and 64 bit Windows

I rather doubt that the operating system has anything to do with it, because loads of people are running Vensim in 64bit environments.
by tomfid
Mon Jun 03, 2013 4:18 pm
Forum: Vensim
Topic: QUEUE FIFO with items going on hold
Replies: 7
Views: 4241

Re: QUEUE FIFO with items going on hold

If I understand correctly, the challenge is that items need to jump in line into the queue, according to their age? I'm guessing that this will have to be done with an explicit stock/flow structure, because the QUEUE functions won't permit it.
by tomfid
Mon Jun 03, 2013 4:06 pm
Forum: Vensim
Topic: QUEUE FIFO with items going on hold
Replies: 7
Views: 4241

Re: QUEUE FIFO with items going on hold

Do you really need discrete item age tracking for some kind of tactical planning process, or is this just a part of some larger strategic model, so that some kind of coflow formulation would work? A solution might be possible with QUEUE ... ATTRIBUTE, where the attribute is the creation date of the ...
by tomfid
Sat Jun 01, 2013 3:01 am
Forum: Vensim
Topic: License Vensim DSS
Replies: 4
Views: 3175

Re: License Vensim DSS

There are also volume discounts - let us know if you need a quote.
by tomfid
Fri May 31, 2013 2:49 pm
Forum: Vensim
Topic: Fish Stocking Model
Replies: 7
Views: 5081

Re: Fish Stocking Model

An example ...
fish stocking.mdl
(3.84 KiB) Downloaded 240 times
by tomfid
Fri May 31, 2013 2:23 pm
Forum: Vensim
Topic: Fish Stocking Model
Replies: 7
Views: 5081

Re: Fish Stocking Model

Another option would be lookup + PULSE TRAIN as the trigger. PULSE TRAIN may be a little simpler to use than IF THEN ELSE( MODULO(Time, ... )), as you don't have to worry about roundoff and time step boundaries.
by tomfid
Tue May 28, 2013 6:22 pm
Forum: Vensim
Topic: time deley
Replies: 12
Views: 7827

Re: time deley

level to auxillary-2.mdl
(1.86 KiB) Downloaded 342 times
by tomfid
Tue May 28, 2013 2:20 pm
Forum: Vensim
Topic: time deley
Replies: 12
Views: 7827

Re: time deley

You could probably break the simultaneity by using 0*SMOOTHi(input,1,1) instead of just input. The smooth contains an internal level, and initializing it to a constant will break the simultaneity.
by tomfid
Tue May 28, 2013 4:02 am
Forum: Vensim
Topic: SimSetup in VenSim6.1
Replies: 1
Views: 1729

Re: SimSetup in VenSim6.1

Sorry Dale - we definitely haven't removed anything. Must be a glitch. We'll sort it out ASAP. - Tom
by tomfid
Tue May 28, 2013 2:10 am
Forum: Vensim
Topic: time deley
Replies: 12
Views: 7827

Re: time deley

There are two options - use the :IGNORE: keyword, or just use the variable in the equation, multiplied by zero - for example,

fakeStock = inputA*inputB + 0*ignoredRate
by tomfid
Mon May 27, 2013 5:57 pm
Forum: Vensim
Topic: stop generation of .vdf file
Replies: 6
Views: 3292

Re: stop generation of .vdf file

It's probably possible to do some simple MOO using Vensim tools, but there isn't direct support for things like finding the Pareto frontier.

Have you succeeded in hooking the two together yet? Are you using the .dll or DDE?

Tom
by tomfid
Mon May 27, 2013 3:48 pm
Forum: Vensim
Topic: time deley
Replies: 12
Views: 7827

Re: time deley

You can violate diagramming conventions by using an auxiliary (i.e. instantaneous) variable and showing it with a box on the diagram. Either, - right-click an auxiliary on the diagram, and change its shape to "box" or, - in a level variable, using the equation editor, change the variable t...
by tomfid
Sun May 26, 2013 1:14 pm
Forum: Vensim
Topic: Linear Program
Replies: 14
Views: 7428

Re: Linear Program

Great! I didn't think of that.

Let me know if you have specific thoughts about desired functionality.
by tomfid
Fri May 24, 2013 5:22 pm
Forum: Vensim
Topic: [HELP] error with million value
Replies: 7
Views: 4697

Re: [HELP] error with million value

There's a workaround for this if you use Double Precision Vensim. In that case, the file format still stores floats, but (optionally) values can be imported from .cin or spreadsheet files as doubles.
by tomfid
Thu May 23, 2013 1:11 pm
Forum: Vensim
Topic: [HELP] error with million value
Replies: 7
Views: 4697

Re: [HELP] error with million value

Again, this is normal behavior - scientific notation. In DSS, the display of numbers in tables is controllable (right-click the table tool and select "Pretty" or "Scientific" number format). But large numbers in the model equations are always stored in floating point format. In a...
by tomfid
Wed May 22, 2013 5:36 pm
Forum: Vensim
Topic: How can i replace the optimization algorithm?
Replies: 27
Views: 10226

Re: How can i replace the optimization algorithm?

Have you upgraded Vensim in the interim?

What is the symptom of the failure? Does the vensim_command() with the LOADMODEL return 0, or are you unable to load the dll or call the function at all?
by tomfid
Wed May 22, 2013 12:52 pm
Forum: Vensim
Topic: One-to-Many allocation problem
Replies: 3
Views: 2079

Re: One-to-Many allocation problem

I think constraining the rate of change of production, rather than an actual scheduled production rate, is adding a level of indirection that I'm not following. If you can post a submodel implementing this, it would be helpful.
by tomfid
Tue May 21, 2013 10:53 pm
Forum: Vensim
Topic: One-to-Many allocation problem
Replies: 3
Views: 2079

Re: One-to-Many allocation problem

How about if you just surround AdjFGI with a MAX(0,...) or IF THEN ELSE() that prevents negative values? Have you check the ALLOCATE sample models in the help system? Also see the Allocation section, http://www.vensim.com/documentation/allocation_overview.htm This case can probably be handled by ALL...
by tomfid
Tue May 21, 2013 3:09 pm
Forum: Vensim
Topic: [HELP] error with million value
Replies: 7
Views: 4697

Re: [HELP] error with million value

This is scientific notation, http://en.wikipedia.org/wiki/Scientific_notation

2.53e+6 = 2.53 * 10^6 = 2.53 * 1,000,000 = 2,530,000

Excel understands scientific notation, so there's no problem exporting the results for further calculation.
by tomfid
Sat May 18, 2013 11:50 pm
Forum: Vensim
Topic: How to set optimisation option
Replies: 2
Views: 1903

Re: How to set optimisation option

How large is large? You can't expect much from models with multiple optimal and high parameter dimensionality.
by tomfid
Sat May 18, 2013 11:19 pm
Forum: Vensim
Topic: Vensim PLE plus and Excel 2010
Replies: 19
Views: 13279

Re: Vensim PLE plus and Excel 2010

Actually they don't need to be shadow variables (unless appearing more than once on a diagram), but often they are used that way. Sounds like a good topic for a quick video clip ...
by tomfid
Sat May 18, 2013 6:05 pm
Forum: Vensim
Topic: Vensim PLE plus and Excel 2010
Replies: 19
Views: 13279

Re: Vensim PLE plus and Excel 2010

The syntax of a lookup is just like a function call, e.g. y = f(x), where f() is the lookup. A quick trip through the User Guide chapter linked above may help with this. In your case, you need a Lookup: dwg rate lookup = GET XLS LOOKUPS('ROI.xls','project' ,'E','F4' ) and an Auxiliary that uses the ...
by tomfid
Fri May 17, 2013 8:34 pm
Forum: Vensim
Topic: Vensim PLE plus and Excel 2010
Replies: 19
Views: 13279

Re: Vensim PLE plus and Excel 2010

The user guide has a chapter on lookups: http://www.vensim.com/documentation/usr08.htm
by tomfid
Fri May 17, 2013 4:35 pm
Forum: Vensim
Topic: Vensim PLE plus and Excel 2010
Replies: 19
Views: 13279

Re: Vensim PLE plus and Excel 2010

This is pointed at the wrong filename, but as soon as I change it to 'roi.xls' it works fine. An easy way to do that is to give it a query name flag, like '?roi', so that it'll ask you to locate the file on first use.
by tomfid
Fri May 17, 2013 4:03 pm
Forum: Vensim
Topic: How can i replace the optimization algorithm?
Replies: 27
Views: 10226

Re: How can i replace the optimization algorithm?

For maximum speed in the dll, you should run using the SYNTHESIM commands rather than ordinary simulations. http://www.vensim.com/documentation/25172.htm http://www.vensim.com/documentation/25531.htm http://www.vensim.com/documentation/25532.htm Turn AUTO off and use GO to launch simulations, after ...