Introduction to Optimization Introduction to Optimization

ancmat02.qxd 11/16/06 3:25 PM Page B10B10 • SUPPLEMENT BINTRODUCTION TO OPTIMIZATIONFIGURE B-4Solver Parameters box (empty) Solver OptionsSolver provides many optionsfor the solution process. ForLPs, the two most commonlyused are Assume LinearModel and Assume Non-Negative.they either have not fully understood the problem or developed an algebraic formulationor have not developed a correct and flexible spreadsheet model.The Target Cell is the cell that you want to maximize or minimize. That is, it representsthe objective value of the model. In this example, cell D8 calculates the profit obtainedfrom some combination of camshafts and gears. The Target Cell must alwayscontain a formula; otherwise Solver generates an error message. To specify D8 as theTarget Cell, either click on cell D8 directly or type “D8” into the Target Cell field. Thenmake sure the radio button on the “Equal To” line is set to “Max.” There are threechoices on this line, but we will only deal with maximizing and minimizing problems.Click in the “By Changing Cells” field. The Changing Cells represent the decision variablesof the model—in our case, the numbers of camshafts and gears. These values arestored in cells B5 and C5. The easiest way to enter these into the By Changing Cellsfield is to simply select them directly in the spreadsheet using either the mouse to selectboth cells or by clicking on one cell, holding down the Shift key, and then usingthe keyboard arrow keys to select all of the pertinent cells. Alternatively, the range“B5:C5” can be typed directly in the dialog box. The Solver Parameters box to thispoint is shown in Figure B-5. Note that if you type in the cell references directly forthe Target Cell and the Changing Cells, you do not have to type in the “$” characters.This is one feature where it doesn’t matter if you use absolute or relative cell referencing(see Supplement A for more information on absolute and relative references).Entering the constraints is slightly more complicated, but not difficult if thespreadsheet model is designed well. To enter a constraint, click the “Add” button. Abox appears, as shown in Figure B-6. A constraint in Solver consists of three pieces ofFIGURE B-5Solver Parameters box (partiallycomplete)