On the page CoG Settings the user can set the basic inputs to create the solution.
In the General Settings widget you can change settings which are used both in the Multiple DCs Scenario and in the Drive Time Scenario.
CoG Weight Factor - The available options are 'Volume' or 'None'.
'Volume' - Both demand and supply locations (if you have any) are considered in proportion to their loads. Locations with a high demand/supply pull harder on the Center of Gravity than locations with low demand/supply.
'None' - Demand and supply values are not considered. All locations pull with equal force on the Center of Gravity.
Running Cost - You can change this parameter to represent your DC running cost. By default it is filled with the Default Fixed Cost attribute (or 2000000, if the attribute is not specified).
Primary Distribution Cost - You can change this parameter to represent your primary distribution cost. When you hover over the value field, you can see the unit of this parameter (cost-unit/THU/distance-unit).
Secondary Distribution Cost - You can change this parameter to represent your secondary distribution cost. When you hover over the value field, you can see the unit of this parameter (cost-unit/THU/distance-unit).
Transportation Speed - This is the average speed of the modes of transport calculated from the input data. When you hover over the value field, you can see the unit of this parameter (distance-unit/hour).
Move to closest cities - When solving the Number of CoGs scenario, the Centers of Gravity can end up in e.g. the middle of nowhere, or in the sea. However, it can be more realistic to consider the closest real city for each Center of Gravity found. So, if you turn on the 'Move to real cities' switch, the app will move the found Centers of Gravity to the closest real city. All the driving times and costs are updated based on the new locations.
Settings - Drive Time Scenario¶
For the Drive Time Scenario there are some specific settings. The default values for these settings are set up to give a quick (rough) solution to start from. Adjusting the settings can give you a more precise solution, but it may also take considerably longer time to solve.
Grid refers to the generated locations used to solve the model. Time limit controls to how long the computation will go on before giving the best answer found so far. Optimality Gap settings control how close the given answer must be to the true best answer.
Time Limit - After this amount of time, the solving of the model is interrupted, even if the desired MIP Gap is not reached yet. The default value is 0.08 hour (so, approximately 5 minutes).
Optimality Gap [Input] - Indicates how fine the solution should be. A lower Optimality Gap gives a better solution, but it also increases the solving time. For example, if the Optimality Gap is 5% and the optimal solution is 20 CoG's, then the solve will finish when a solution is within 5% of 20 (so, for 20 + 1 = 21).
Optimality Gap [Output] - After the solve, this parameter indicates the Optimality Gap of the given solution. This can be greater than the input gap when the time limit stopped the solve before the best solution was found. The output gap is less than or equal to the input gap when an allowed solution was found within the time limit.
Grid Distance - The distance between two locations in the grid. A smaller grid distance gives a better solution, but it also increases the solving time. Grid cities are generated based on the Grid Distance setting and the Maximum Drive Time. The cities close to a real grid are selected and cities which cannot be part of the solution are excluded (e.g. when there is no customer location within the maximum driving time distance).
Extend Search Area - By default this setting is off. Turn it on to extend the search area to a margin equal to the driving time distance. This can give a better solution in some cases, but it also increases the execution time. This setting can be of interest when e.g. you have a subset of locations near the border of the 'rectangle' around your data, but no cities close to that subset, while there are cities outside the area (and close to the subset).
Data Passes Date Limit - When your locations are close to the International Date Line (longitude ~ +/- 180 degrees) and they are on both sides of the date line, turn this switch on. In this case, the distance calculations will be allowed to cross the date line.
To the right side of the settings widget, there are four columns of widgets which allow you to select elements to be included in Center of Gravity calculations. Each column represents some Customers/Suppliers/Products/Periods, and has a group element selector and an individual element selector.
If a group element is selected/unselected, the single element which belongs to this group is also selected/unselected.
If a single element is unselected, the group which the single element belongs to is also unselected.
If all single elements in a group are selected, the group element is also selected.
This option is visible only when you have existing warehouse locations. In that case, if you want to keep some of them fixed in the calculations, you can set these locations here as CoG. When running one of the CoG scenarios, each fixed location will be one of the resulting CoGs.