Building Orientation
The building orientation indicates to which of the possible three axes of the hexagonal adjacency graph the building width dimension is parallel. The adjacency graph has three main axes, horizontal or level, 60 degrees upward, and 60 degrees downwards of the horizontal level. The block layout construction algorithms will create a layout by putting departments in rows, where the rows are parallel to the building width dimension. Departments whose positions in the adjacency graph are on the same axis will be placed in the same row in the block layout.
Exchange Improvements
After the original block layout is constructed five possible improvement steps can be executed. The options are none, steepest descent two exchange and three exchange, and annealing exchange two exchange and three exchange.
None does not execute an improvement step.
Steepest Descent exchange attempts to improve the graph in deterministic and greedy manner by attempting two or three department exchanges. The exchange with the largest savings among all possible combinations of two or three departments is determined and if these savings are positive then those two or three departments are exchanged. The process repeats until no further improvements can be made.
Two Exchange attempts to improve the layout in a steepest descent manner by attempting two department exchanges. It computes the savings generated by removing two departments out of the graph and swapping their position. The savings are based on a decrease in the shape adjusted distance score. Three Exchange attempts to improve the graph in a steepest descent manner by attempting three department exchanges. It computes the savings generated by removing three departments out of the graph and swapping their position. The savings are based on a decrease in the shape adjusted distance score.
Annealing Exchange attempts to improve the graph in stochastic, non steepest descent manner by attempting two or three department exchanges. It computes the savings generated by removing three departments out of the graph and swapping their position. The savings are based on a decrease in the shape adjusted distance score. The two or three departments are chosen at random. If the savings are positive then the exchange is made. If the savings are negative, i.e. the shape distance score is higher, then the exchange can still be made with a certain probability depending on the how long the simulated annealing algorithm has been executing. The process repeats until no further improvements can be made.
For further information on two and three exchanges see the Block Layout section in the Algorithms chapter and Goetschalckx (1992). For further information on simulated annealing see Kirkpatrick et al. (1983) and Vechi and Kirkpatrick (1983).
Computational processing time increases sharply with the amount of improvement processing. Since the computation of the upper bound may require a significant amount of time, the program allows you to limit the maximum execution time with the Time Limit command of the Edit menu or by pressing the Parameters button.
Space Allocation
The Layered space allocation method divides the building area in strips or layers parallel to the orientation of the building. All departments located on an axis of the hexagonal adjacency graph parallel to the building orientation are assigned to a single layer. The algorithm then assigns department areas from left to right in each layer.
The Tiled space allocation method divides the building area into a set of non-overlapping department rectangles. The position of the department rectangles is derived from the hexagonal adjacency graph. The Tiled space allocation method has more flexibility than the Layered space allocation method and will yield on the average layouts with a lower distance score. However, the resulting layout may not have the structure that allows parallel material handling aisles. There is no guarantee that the Tiled space allocation method will yield a lower distance score than the Layered space allocation method for a particular layout project. Because the Tiled method examines many more alternatives than the Layered method, it requires substantially longer computation times.
Parameters
All layout improvement parameters can be set by pressing the Parameters button. The Exchange Parameters dialog window will be shown.