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Q&A’s – Questions and Answers about VORSIM and VORSIM-built Models

1.      How is VORSIM 14 different from earlier versions?  Version 14 has all of the virtues of earlier versions such as:  quitting a model automatically switches you to the Solution Manager Control screen, when you click the [Model] button on any control screen; you get a menu of saved models, etc.  Most important, VORSIM 14 runs in Excel 2000-2010.  The control screens have been redesigned a bit and some symmetry options have been added to equation workbooks.

2.      How is VORSIM 15 different from version 14?  Excel 2013 changed its file formats from *.xls to *.xlsx for data files and *xlsm for files containing macros.  VORSIM 15 accepts these changes and builds upon them.  In addition, VORSIM menus were replaced by Tool screens.  The file nomenclature difference between versions 15 and 14 means that the software and generated files do not work in the Excel version of the other; e.g. VORSIM 15 will not work in earlier versions of Excel and VORSIM 14 will not work in Excel 2013.  However, VORSIM 14 workbooks can be converted to VORSIM 15 nomenclature.

3.      Will models built in an earlier version of VORSIM work in VORSIM 14?  Yes, most things should work in VORSIM 14 even though a few button positions and labels may differ from those in earlier versions.  The only change really needed is the writing of indicator variable names in the indicators workbook.  There you have to add either ! or [..] before your variable names if you want to re-write indicators, however this a small editing change and can be done in a few minutes.  You also might want to rebuild your solution file with the pull-down or Add-Ins menu item of that name on the Solution Manager control screen.  Send us your old model ( if you have problems running your older model in VORSIM 14 and we can help with any needed conversions for a charge.  Conversion is also required to work with a version 14 and earlier model files in VORSIM 15.

4.      Can I build large models in VORSIM?  Yes models can easily be built with a few thousand variables if needed.  You can also build a small model and expand and enlarge it later.  There is a limit of 100 “change” and “target” variables that can be entered; however in an economic model for example, that can mean a maximum of 100 markets to be cleared BUT thousands of equations can be used to model those 100 markets.  If you do build a model with more than 100 change and target variables, you may need to purchase a larger Solver from Frontline systems (see ‘Sources’).

5.      Is VORSIM a model or a modeling system?  VORSIM is a set of computer programs, which help you build models using the Excel spreadsheet as a model platform, i.e. it is a modeling system rather than a model.  The model you build will be set of Excel workbooks containing programs for the control and simulation of the model.  As you build a model, you create separate workbooks for the definition of your model structure and nomenclature, for the data, and for the model equations.  Solutions are saved as named Excel workbooks.  In addition many other model related files exist as Excel workbooks.  VORSIM guides your organization of all of the information about your model in an efficient way.  Each model has its own directory where all relevant information is kept.  As a modeling system, VORSIM helps organize models and related information in the Excel spreadsheet environment.

6.      Can I put formulas (which calculate cell values from other cell values) into a data workbook?  Yes.  Numbers (not formulas) are taken from the data sheet for: a) entry into the Basedata sheet of the equation/parameter workbook, and b) entry into the historical and exogenous data workbooks that are created along with a model.  For example, if your model requires say a world trade balance, you can use formulas in the data workbook to achieve this; but the numbers generated by data workbook formulas would be used for model initialization.

7.      Sometimes people cannot run VORSIM models that others have created.  What is the problem?  When working with a model in a drive or directory other than the one in which it was created, models sometimes give a compilation error (an Excel VBA error).  These errors occur because Excel linkages in your computer are different than those in the computer where the model workbook was created.  However, the solution is likely to be simple.  Use the |Update Links in Selected File| item in the VORSIM menu on the Model Manager control screen to change the linkages.  Also you may need to re-created model or equation files on your computer – a simple operation, provided you have backed up everything and can restore you data and equations into your re-created workbooks.  Models that come with VORSIM are not configured for solution; you have to do that yourself buy pressing the suggested configuration button on the model spreadsheet.  This insures that the linkages to Excel on your computer are used.  If you give a model to another VORSIM user on another computer, it is good practice to not configure the model for solution – let the recipient do that.

8.      Can VORSIM be used to build quarterly or monthly models?  Yes, VORSIM can easily handle models built with annual, semi-annual, quarterly, or monthly data.  For annual data, you simply enter the time period as an integer (e.g. the year); however if you are building a non-annual model, just use 1, 2, 3, etc. for your time periods.  When you have finished building your non-annual model, use the VORSIM menu in the Model Manager control screen to add quarterly, semi-annual, etc. time tags to your model workbooks.  You will have a completely documented and readable model with appropriate time tags.

9.      Can I put equation parameters outside of a parameter matrix?  The line above, the line below and columns to the right of an equation parameter matrix are saved along with the parameter matrix.  Therefore you can put parameters outside the matrix, provided your parameters are adjacent to the matrix.  Any information outside of the adjacent area will be lost when the equation is banked and then restored.

10.    Are there special problems with a very large model in VORSIM?  The most important thing to consider is the number of constraints (target cells) for solution.  The Excel Solver that comes with VORSIM has a limit of 100 constraints for a model (even so, a model with 100 constraints, e.g. 100 markets to clear, can still have thousands of equations).  Therefore the limit of model size is only the number of rows and columns available in the version of Excel you are using.  Keep in mind that many model-building operations and model solutions are slower for large models.

11.    Can I upgrade my current version of VORSIM to version 14 or 15 without paying the full purchase price for a download version?  No but VORSIM 14 and 15 are very cheap.  However if you have a documented problem with version 15, we will fix it and give you a fixed copy free of charge. 

12.    How do I diagnose solution problems with my model?  Note any messages that occur such as “infeasible solution”.  This may just mean that convergence criteria are too tight.  Try solving the model and see if markets clear – this sometimes happens even if the ‘infeasible’ message comes up.  Read about solution problems in your Excel manual and the Frontline website.  Depending upon the message, there may be a Solver parameter that you can change (use the Solver pull-down menu or reassemble the model and change the parameters on the {Solver parameters} sheet.  For example, you might need to apply scaling to you model for solutions purposes (adjusts for widely different change variable values in the solution process).  If a change in a Solver parameter does not help, the problem may lie with your model structure or parameters.  Finally, there are some options which can be used to constrain model variables to remain within a certain range.  You also should try to use a master target variable to keep your solver going on large models.

13.    Why can’t I view at the VBA code for VORSIM so that I can edit it for my use?  VORSIM is written for Excel using VBA (Visual Basic for Applications), the macro language of Excel.  VORSIM is a copyrighted program and those licensing it do not have legal access to the code.  From a practical viewpoint, VORSIM programming is complicated and if we allowed users to change it, they could easily make changes that would prevent VORSIM programs from working at all.  If you want to add your own VBA routines to your VORSIM model, consult some of the publications cited in sources for further information.  You are perfectly free to add programs of your own to model workbooks.

14.    Why won’t my VORSIM-built model run in Excel?  The first thing to check is your security settings.  For example, Office XP has an extra security level for Visual Basic Projects (a VORSIM-built model is such a project).  Until you give Excel access to Visual Basic Projects, you will not be able to attach the necessary programs to you model for manipulation and solution.  To do this, go to the Tools Menu, find Macro and click on Security.  This brings up a Security menu and you must select high, medium, or low security options.  You cannot select the “high” option if VORSIM is to work at all.  If you select medium security, you will get a warning message when a VORSIM program is run (annoying but one can live with it).  To avoid this problem completely, you need to select the lowest security level in for Excel macros.  Next, you must allow access to VBA Projects.  Select the “Trusted Sources” tab and check both (if you have both) of the items at the bottom of the menu: “Trust all installed add-ins and templates” and “Trust access to Visual Basic Project”.  Then from your model equation (eqp) file, re-build your model.  It will contain the correct programs for solution.  You can learn more about security problems by reading the file on Excel security in this website.  In addition if you are using McAfee anti-virus program, you must permanently turn off real time scanning before you install VORSIM.  McAfee real time scanning tosses out a couple of *.bas files that are required for model building. 

15.    I get an error message when I try solving my model for the first time.  What do I do?  Most solver related problems like this occur because the version of the Solver that comes with version 14 of Excel does not handle VBA Solver commands properly.  First, make sure that the Solver Add-in is installed with Excel by clicking on the Tools Add-in menu and select Solver Add-in.  If you do not see the Solver add-in on the menu, you need to re-install Excel with the manual option and make sure the Solver gets installed.  Once you have the Solver installed it is usually found in the Programs/Office/ Library/ Solver menu.  The VORSIM Solver.xla file should be 647 KB.  If your solver is smaller than this, execute the Solver.exe program in your VORSIM folder.  This should install the correct Solver (647 KB), backing up the existing one.  If this program does not work, then manually copy the 2 solver files in your VORSIM directory (Solver.xla and Solver32.dll) to replace those in the Solver library under your Office folder.  Then re-build your model from your equation workbook. If you are using VORSIM 15 you will automatically use the accompanying solver so installation problems should not occur.  Then you must deal with solver error messages..

16.    Sometimes when a program creates a workbook, it stops without completing the routine.  What could be wrong?  When a VORSIM program creates a new workbook, it formats the pages (sheets) for printing.  If your default printer is not turned on, the program may stop; just turn on your default printer.

17.    I specified my model with a lagged variable but did not actually use a lagged variable in an equation.  I created and simulated the model.  Next, I modified the equation to include a lagged variable but the equation is NOT written correctly when the model is created. What is wrong?  Here is a situation where a time-saving feature of VORSIM can cause a problem.  The FIRST time you create a dynamic model, VORSIM writes two history workbooks (e.g. DEMOhist.xls and DEMOhist.sol) using the data available.  These workbooks are NOT re-created when the model is re-created.  However they are deleted when the Basedata is updated in the equation workbook.  So if you later added the lagged variables to equations, just update the Basedata sheet, re-write the equations, and re-create the model (all click-of-the-button routines).

18.    I have some small numbers in my database which seem to become zero when they are gathered into the Basedata sheet of the equation workbook.  I want these numbers to remain non-zero when equations are written.  How do I deal with this problem?  The answer is simple; manually change the format for the relevant variables in the data workbook.  Data cell formats are originally set in the definition workbook.  But once the data workbook has been created, they can be changed manually.  If numbers are smaller than those anticipated when the data workbook was originally created, simply manually change the formats with the Excel Format menu by increasing the number of digits after the decimal point.  The format of a cell in the data workbook is also the format of the cell in the Basedata sheet in the equation workbook.  So once you have increased the number of digits after the decimal point in the data workbook for small numbers, these numbers should carry along into the equation workbook and be available for use in equations.

19.    I set a network printer as the default and all of a sudden I had problems creating a model.  I would get error messages and the program would stop.  What is the problem here?  VORSIM programs format files for printing (including the model file itself) when they are created.  If your computer is connected to a non-local (i.e. network) printer and there is no feedback from that printer, some programs may stop.  The fix is simple, just set a local printer as the default; preferably it should be the one attached to your computer’s printer port but it might be another local one installed, such as Adobe Distiller – which can receive print.

20.    Can I use IF statements in model equations?  Yes but be careful.  You can write equations using the functions listed on the Variables sheet of the equation workbook, but take care to check the required format of the function with VBA help; you must have the correct syntax for the functions to operate properly.  And remember, discontinuous functions may lead to solution problems.

21.    I have a problem with the SUMPRODUCT function in my model; I want to use it so I don’t have to write long equations but sometimes it does not seem to work.  One form that does work in VORSIM is as follows:  SUMPRODUCT((A5:A20)*(C10:C25)).  Put parentheses around the two ranges to be multiplied and use the multiplication sign * between the two parenthesized ranges.

22.    I get the message “VORSIM locked for editing…” when I try to operate on a model for workbook.  This error occurs at times when, in effect, two versions of VORSIM or a model file are open. One solution is to close one of the files.  One problem with VORSIM 14  might be that there are stray VORSIM files elsewhere than in the VORSIM directory (or possibly there are more than one VORSIM directories created during installation).  One thing to try is to uninstall and re-install VORSIM AFTER you have run the “Check Stray Files” program in the VORSIM windows.  This will help you eliminate extraneous VORSIM files.  To uninstall VORSIM, go to the VORSIM directory and click the “unstall.exe” program to uninstall VORSIM.  For recent versions of VORSIM, delete it from the control screen delete programs option.  Note that when it is deleted, desktop and start menu icons may have to be removed manually.

23.    Sometimes I get a message “ a read-only file..” when I am carrying out a VORSIM operation on a model workbook.  When files have been copied from another source, often they are marked as ‘read-only’ to prevents them from being changed.  All you have to do is to go to Explorer and right click on the file and choose its properties.  Remove the ‘read-only’check and you will be able to operate on it with VORSIM.

24.    When I replicate a model or when I create a data workbook with links to other files (original data), I have a problem after a model is created; I am not able to configure the model.  What is wrong?  The data workbook can contain formulas BUT only formulas which relate to variables in the data workbook.  If the data workbook contains formulas which link to another workbook, this causes problems in writing the exogenous data file.  The solution is to remove the linkages to other workbooks in the data workbook.  This can be done by editing the links or by loading the data workbook from the Solution Manager control screen and using the VORSIM pull-down menu to remove ALL formulas in the data workbook. You may want to keep a backup of the data workbook with the linkages to other workbooks saved under another name.

25.    Once I have set the solver parameters in a model, can I change them?  Once the solver has been installed with the model, the solver parameters have been set at the values you left in place on the solver parameters sheet.  Furthermore, this sheet is removed from the model.  HOWEVER, if you unprotect the model sheet and workbook, you can view the solver parameters menu you set by using the Solver item on the Tools menu.  You can then change solver parameters on this menu and resolve the model from the menu with the changed solver parameters.  If you get a satisfactory solution, then since this is equivalent to testing the solver by solving for the base period, you should click the [Solve **mod] button to do a final model solution.  Note that testing the solver while solving the model does not prepare a solution to be saved as a *.sol file – this is done ONLY when solutions are obtained by the [Solve **mod] button. 

26.    Can I use the regular pull-down Solver menu to set solver parameters and solve my model?  Yes, once the [Test Solver] button has been clicked, the solver will be activated.  First you MUST unprotect the model sheet and workbook.  Then you can click on the Solver item on the pull-down menu and use buttons on it to change solver parameters and solve the model.  This procedure does not save the parameters you set permanently but does use them for model solution when you clock “Solve” on the menu.  This is a good procedure for determining the parameters for the Solver on your model.  Once you have satisfactory solver parameters, re-build the model, permanently set the new parameters, and install the solver again.  Remember that this method only solves for one time period.  You need to use the VORSIM solve routine for a dynamic model which is solved progressively over time.  With VORSIM 15, procedures may differ a bit.

27.     How do I find errors in my model?  There are several features of VORSIM which can help you.  First, when you write equations in the equation workbook, some equation errors will be highlighted as equation intercepts are calculated.  For example, a message saying that no data was found on the Basedata sheet means that either a) the variable name was incorrectly spelled in the matrix generating the equation or b) no data for the variable has been entered into the data workbook (and subsequently copied into the Basedata sheet in the equation workbook).  A message that no Basedata sheet data was found for a dependent variable means just that – and the equation will not be written.  You can visually check equations after they are written to see that they are what you intended.  You can also view the Excel version of the equations in the B column – these should have only cell addresses, not variable names.  Finally, look at the equation intercepts to make sure they make sense.  For example, an equation which reads “0*EUqtWHT…” has a zero intercept and will always give a zero value – often this means that the equation has a syntax error – count your parentheses so the number of left and right handed parentheses are the same.  Sometimes a constant term value of 2007 means there is an equation problem.  When equations are written and the intercepts are calculated, the Excel syntax is used and an unexpected intercept value usually means something is wrong with the equation syntax (Excel interprets the incorrect syntax in a way that yields an odd intercept value).  Finally, syntax errors can show up when equations are written into the model.  Sometimes equations are flagged and the writing routine stops.  When all errors have been found and corrected and equations have been successfully written into a model, there still can be errors which will cause solution difficulties.  The most common error is that equation intercepts are wrongly calculated so that the base value calculated by the model equation for a variable does NOT equal the base value in the Basedata sheet of the equation workbook.  The Model Manager VORSIM item - |Compare Model with Basedata Values| - is very helpful in highlighting problems.  It calculates a file of the difference between the model base values and the Basedata values – any equation (yellow) cell containing a non-zero value highlights a potential problem.  If base values calculated by the model do not equal Basedata values in the equation workbook, then the model will start solving to find equilibrium BEFORE any policy changes have been introduced.  In other words, the model does NOT start from an equilibrium position.

28.    What improvements have been made in VORSIM 14?  First, improvements from version 12 have been retained.   Routines for model configuration have been improved.  In one new option, you can place upper and lower bounds on ‘change’ variables.  This can prevent model solutions that are “out of bounds” so to speak.  It can also shorten solution time in large models.  Another option allows you to chose an overall target variable; this speeds up solutions for some models.  Other improvements have been made in report writing and model management.  For example, you now can bring in equations from other models in your current model under construction.  Finally, an option has been added to a model so that you can create and use a time series based workbook of exogenous data for changing policy variables for model scenarios.  The original option allows you to change one variable at a time while this new option may allow you to operate on many variables in a sheet using normal Excel methods.  A utility has been added which lists all of the models in the VMOD model directory.  Menus additions include a routine to convert solutions and exogenous data to a time series format.  Most importantly, VORSIM 14 operates fully in Excel 2007 - 2010.  Helpers have been added such as buttons to access the User’s Guide directly from control screens.  Finally, the VORSIM menus in each control screen are accessed from the Add-Ins tab above the ribbon.  More changes and improvements go into VORSIM 15 and these are documented elsewhere.

29.    Will VORSIM 14 operate correctly in Windows 7 and with Excel 2010?  In Vista – YES - VORSIM 14 operates normally in Windows 7.  Downloading or executing the *.exe installation programs may be confronted by the extra security embedded in Windows 7 which may have to be temporarily relaxed.  In Excel 2010 – YES - VORSIM 14 does operate in Excel 2010.  VORSIM pull-down menus are found in the ‘ribbon’ structure (under “Add-ins”) which replaces earlier Excel menus.  VORSIM has not been modified to change the ribbon structure in Excel 2010 but ribbon functions are available in model workbooks just as VORSIM menu items were.  If you want model files generated with Excel 2010 to be compatible with earlier versions, set the Excel file saving option to save workbooks in a form compatible with earlier versions of Excel (97-2003) rather than the Excel 2010 format (which is different from earlier Excel versions).  If you operate VORSIM only in Excel 2010, then you should be able to use its file system

30.    When I try to install the VORSIM Solver in Windows 7, I get a message that the Solver.exe program does not run on a 64 bit machine.  What do I do? The software that created Solver.exe works only for a 32 bit machine.  However you can add the solver manually with the following steps.  Find the Excel Solver folder (usually in the Microsoft Office\Office12\Library\SOLVER folder or something like this).  Rename Solver.xla to Solver.bak and Solver32.dll to Solver32.bak.  Then copy Solver.xla and Solver32.dll from the VORSIM folder to the Excel Solver folder.  This should do the trick.

31.    When I try to create a model I get an error “runtime # 9, subscript out of range”, what is going on here?  VORSIM has tried to execute a command which uses a file name (which has been programmed in English) but does not recognize the English word.  If you are used a non-English keyboard and input option, go into the control panel, range and language options, and choose US English.  Then VORSIM will again recognize its English input and the message will disappear.

32.    When I install VORSIM, I get multiple copies of icons in the VORSIM Utilities Window.  Why?   You probably had an earlier version of VORSIM installed.  Installation may add new icons to the old set.  You can either a) manually delete extra icons (careful not to delete the wrong ones) or b) manually delete the icons in the window and re-install VORSIM.

33.    How have you changed the Report Writer? As before, the user designs reports.  But once a report (*.rpt) is saved, different methods of data transfer can be used to put solution or other data into a report.  Blocks of data can be copied with or without a format, linkages to source data can be created in the report, or movelists can be created to transfer data.  Once data blocks are put into a report, their source information is kept in a comment in the block.  Then the sheet can be updated automatically with newer source data by simply using the UPDATE… command in the VORSIM pull-down menu or Add-Ins menu to find and recopy the source data.  This flexibility in methods of data transfer into a report will save considerable time in report preparation.

34.    Does VORSIM work in Excel 2013?  Yes with VORSIM 15! Yippee!  This is explained on the VORSIM 15 website.  Many changes were made using Excel 2013 features.  Model solutions are more robust and obtained faster in VORSIM 15 than in VORSIM 14 or earlier VORSIM versions.

35.    Will models build in VORSIM 14 or earlier versions work in version 15?  Generally yes, if key files are converted to the VORSIM 15 format and sheet linkages are changed.  The file nomenclature has been changed in VORSIM 15, compared to versions 14 and earlier, hence worksheets have to be renamed.  The Model Manager B button in the VORSIM 15 Model Manager control screen helps you with this conversion.  The [Modify Links …] button lets you systematically change links from older VORSIM files to the VORSIM 15 versions.