Search found 148 matches

by RWTH_FCN
Fri Jan 24, 2020 4:08 pm
Forum: Vensim
Topic: Hearne' method
Replies: 6
Views: 4057

Re: Hearne' method

I assume you mean this? https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1939-7445.2009.00058.x Is it possible to use this method in an electricity market. I have a large-scale model which takes hours for one run, so I even cannot use Monte Carlo for sensitivity analysis. That's why I was wonderin...
by RWTH_FCN
Fri Jan 24, 2020 3:11 pm
Forum: Vensim
Topic: A question about calculating median
Replies: 6
Views: 2915

Re: A question about calculating median

tomfid wrote: Thu Jan 23, 2020 3:04 pm How often do you need to update it? There might be a way to create a function to access it occasionally (e.g., monthly updates), so that the load is lower.

Is there some other robust statistic that would work?
Yearly. I want to report yearly median price of electricity for 14 regions in Europe.
by RWTH_FCN
Thu Jan 23, 2020 10:54 am
Forum: Vensim
Topic: A question about calculating median
Replies: 6
Views: 2915

Re: A question about calculating median

If you're running with a 1-hr time step, this will be VERY expensive computationally, because you'll be sorting an array of 8760 values every time step. If the time step is larger, and the hour dimension is already in an array, it might work. Yes, I am running with a 1-hr time step for 35 years and...
by RWTH_FCN
Sun Jan 19, 2020 6:44 pm
Forum: Vensim
Topic: A question about calculating median
Replies: 6
Views: 2915

Re: A question about calculating median

You can report the median with the Stats tool. If you need it dynamically, you store values in an array and use the VECTOR SORT-type functions to find the midpoint. I want to use second method but I get error yet. My hourly price is a stock and its flow is price change this to next hour . Can you p...
by RWTH_FCN
Tue Jan 14, 2020 6:20 pm
Forum: Vensim
Topic: A question about calculating median
Replies: 6
Views: 2915

A question about calculating median

Hi, My model simulates electricty market hourly from 2015-2050 for different countries. So it produces hourly price for each year. I was wondering how can I extract median electricity price per year? My regional price for every hour is as follows: Regional Price this hour[EndUse Region]= INTEG ( pri...
by RWTH_FCN
Sat Dec 07, 2019 5:36 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14885

Re: Integrating time step of optimization problem

Ah - that explains the difference. Seems like a weird way to run a market, but if those are the rules, those are the rules. Here's an idea: Suppose generators bid at cost + markup Make the markup a stock, which bidders adjust according to some pressures - e.g., maintaining a desired utilization (su...
by RWTH_FCN
Fri Dec 06, 2019 11:56 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14885

Re: Integrating time step of optimization problem

Is there a reason to to have bidders bid at their own marginal cost, per theory? Its not competently marginal pricing because in discriminatory auction like pay as bid (PAB) auction bidders bid at least their cost ( it could be marginal cost or LCOE) plus a mark-up. Actually, the higher the bid, th...
by RWTH_FCN
Fri Dec 06, 2019 6:06 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14885

Re: Integrating time step of optimization problem

Not sure where the original thread is, but I think the problem may be that inclusion of expected price in bid formation is not rational or competitive, hence the apparent violation of theory. Yes, its related to the expected price. Actually, there is a trade-off for bidders which they trade-off bet...
by RWTH_FCN
Fri Dec 06, 2019 4:40 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14885

Re: Integrating time step of optimization problem

I've attached two models, neither of which is really right, but both in the ballpark. DEMAND AT PRICE elec 2.mdlDEMAND AT PRICE elec 1.mdl #1 implements what I originally suggested, which is that everyone bids close to MAX( marg cost, expected price ). That actually implements collusion, and the pr...
by RWTH_FCN
Wed Nov 20, 2019 4:34 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

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. Sorry for late response. Actually, I used increased version of SAVEPER. For my case, as long as the model is huge (simulati...
by RWTH_FCN
Wed Oct 30, 2019 6:39 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

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? I am using 32 bit now. The problem occures when I increase number of iterations. I think your assumption is correct, when size of vdf...
by RWTH_FCN
Tue Oct 29, 2019 6:47 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

tomfid wrote: Mon Oct 28, 2019 5:44 pm Any chance that the disk really is full (or would be, after writing the results)?
I don't think so. Maybe it is related to the size of model
by RWTH_FCN
Mon Oct 28, 2019 5:12 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

Hi,

I did Monte carlo Simulation for a large-scale model, after many simplifications in my model I got this error (it happens at Sensitivity Simulation 1/3):

error writing results-disk may be full

I was wondering is there any solution for it or is it related to size of model?
by RWTH_FCN
Thu Oct 17, 2019 3:56 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

We're working on it, but I'm not sure whether it'll be done by end of year. The speedup is more than noticeable if you have a many-core machine. Older workstations with 16 or more cores are now readily available at dirt cheap prices. We'll keep you posted as this evolves. Thanks for your information.
by RWTH_FCN
Fri Oct 11, 2019 3:01 pm
Forum: Vensim
Topic: Stocastic optimization of large-scale model
Replies: 2
Views: 1716

Re: Stocastic optimization of large-scale model

Your question is a little vague. You can use the Vensim functionality to run optimization/sensitivity, but obviously your external functions are your responsibility, only you can answer the questions regarding those. My question was related to using stochastic optimization for a large-scale model w...
by RWTH_FCN
Wed Oct 09, 2019 11:55 am
Forum: Vensim
Topic: Stocastic optimization of large-scale model
Replies: 2
Views: 1716

Stocastic optimization of large-scale model

Hi, I have a large-scale model (huge input data and long run) for electricity market, which minimizes the total system cost (I have an external function for this minimization function). I want to include uncertainty in the model and consider some parameters (assume fuel price) uncertain in order to ...
by RWTH_FCN
Tue Oct 08, 2019 3:06 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

I ran the model on a super computer but since this version does not do any parallel multicore computation, the running time did not reduce. Do you have any plan for releasing that experimental version?
by RWTH_FCN
Sat Oct 05, 2019 2:12 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

We have an experimental version that does parallel multicore execution, which would reduce your simulation time by a factor of the number of cores you have (I have a server with 60, so it does in a minute what normally takes an hour). We could explore that option, though memory might be a problem. ...
by RWTH_FCN
Thu Oct 03, 2019 4:30 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

You can run monte-carlo, but it will probably take you years to run it if a single run takes 7 hours. Each monte-carlo simulation will take 7 hours. Thanks. Do you have any suggestion for modeling uncertainty in such models which take very long in Vensim? Is there any sample model for simulating un...
by RWTH_FCN
Thu Oct 03, 2019 4:06 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

I have a large-scale model that its simulation time is 7 hours (I am using compiler as well). From computational points of view, is it possible to do a Monte carlo simulation on it? Is there any linear relation between "number of simulation" in Monte carlo tab and "time of simulation&...
by RWTH_FCN
Wed Oct 02, 2019 1:06 pm
Forum: Vensim
Topic: Vensim 8 External functions documents & help
Replies: 8
Views: 5872

Re: Vensim 8 External functions documents & help

Administrator wrote: Wed Oct 02, 2019 11:23 am You will need to recompile the DLL using a 64 bit compiler.
Thanks. Sounds reasonable
by RWTH_FCN
Wed Oct 02, 2019 9:26 am
Forum: Vensim
Topic: Vensim 8 External functions documents & help
Replies: 8
Views: 5872

Re: Vensim 8 External functions documents & help

Hi, I have upgraded my vensim to 64 bit and since I am using external fucntions when I want to run it I get this error: [The external function in C:users\vensim\cfiles\venext.dll- could not be loaded. Do you want to try loading again next time?] After clicking "yes" everything is in text m...
by RWTH_FCN
Wed Sep 18, 2019 12:49 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

I found it. The reason was that the variable had subscripts. So I used another variable W/O subscripts and it worked well. Can I ask you how can I do sensivity analysis for variables with subscripts and variables with array dimension? I solved it too. I should have just included subscripts in the ....
by RWTH_FCN
Wed Sep 18, 2019 8:59 am
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

I found it. The reason was that the variable had subscripts. So I used another variable W/O subscripts and it worked well.
Can I ask you how can I do sensivity analysis for variables with subscripts and variables with array dimension?
by RWTH_FCN
Tue Sep 17, 2019 5:14 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16644

Re: sensitivity analysis (vensim)

tomfid wrote: Tue Sep 17, 2019 5:03 pm Sounds like your control file (.vsc) specifies a variable that doesn't exist or isn't constant.
The variable is constant.
I would be pleased to have your feedback about my second question as well.