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Yearstretch GASolver Reference

Input Cell Value Range


Input Cell Value Range

The initial, or seed, range is the range of values allowed for the input, or changeable, cells. GASolver will start the search for a solution to your sheet by using input values from within the range you set.

The setting of input ranges is crucial in minimising the time GASolver will take to reach a best solution. If your data set is large then it takes longer to locate better solutions. If you can narrow the area where those solutions may be found then GASolver can focus on more productive solutions earlier in the search. If your evolution times are long then it is this feature you should concentrate on to reduce them.

If a long time passes without a better solution being found then GASolver can look at each of the input ranges and, if you have allowed it, gradually grow the allowed range of input values to expand the solution search area.

We strongly recommend you also read Using Constraints and Performance Points.

Performance point: The smaller the input cell range the faster the solver will work. The larger the seed range the better the chance of a solution. To get the best of both worlds however try setting a small a range as is practical and then check the 'grow range' option.

Performance point: For faster solutions you can check the 'use integers' option and GASolver will only generate integers which are faster to process than other number types.

The initial input cell range is set for each individual variable in order to better tune the system to your requirements.

To Use Default Initial Ranges:

GASolver can use a default set of input cell value data ranges. For many problems these are a good start however you may change them easily.

  1. Click the button and GASolver will apply the default range conditions to each input cell value creation:

  • set an initial range of -1000 to 1000 for each input cell.

  • set the 'Automatically expand this range' option to true.

  • set the 'Integers values only' option to true.

  • set the 'Non-zero values only' option to true.

To Estimate Initial Ranges from your data:

GASolver can estimate input cell value data ranges from your current sheet values. If your model has sensible values already in the input cells then GASolver will use them to estimate a reasonable start point.

Performance point: Estimating Initial Ranges from your data is a very efficient way of controlling the search as the effect of using this option is to commence the search in the area of your existing sheet solution from where you can allow it to widen as required.

  1. Click the button and GASolver will read each input cell value and:

  • set an allowed numeric range of 5% either side of the value

  • set the 'Automatically expand this range' option to false.

  • set the 'Integers values only' option if the value is already an integer.

  • set the 'Non-zero values only' option if the value is already not zero.

Note that this option does not include your current solution in the search. It only uses the current solution to set the boundaries of the search. To explicitly include the current solution in the search see Include current sheet values in the Solving Options section.

To Modify An Initial Range:

  1. Double-click on the relevant input cell from the Input Cell Seed Conditions list in the main dialog.

the Input Cell Value dialog appears.

  1. Enter the numeric range allowed for this input cell by setting the minimum and maximum values.

  2. If you want GASolver to be able to expand the initial range you have set to search for better solutions then check the Automatically Expand This Range If Required option. If however the input cell values must NOT exceed the initial range specified then ensure that the option is unchecked.

Performance point: Range expansion is rather dangerous in that it can rapidly widen the space within which we are creating solutions so it must be used with care. In fact it should only be used if one can start from a valid solution and then check the range expansion if no better one can be found. If searching for a first solution from scratch then do not use range expansion at all until a reasonable solution has first been located.

  1. If you want a faster solution by using only integers in the input cells then check the Use Integer Values Only option.

  2. If you want to avoid 0 values then check the Non zero values only option.

  3. Click OK.

  4. The input cell value conditions list in the main dialog now shows your choice of range.

  5. Click Apply Input Cell Conditions from the main dialog to apply these new conditions to the solver.

See also Using Constraints, Adding Constraints

 

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