A contour plot of the search space in the context of metaheuristic techniques provides a visual representation of the landscape formed by the objective function being optimized. It is a graphical tool that helps researchers and practitioners understand the characteristics of the problem space and analyze the behavior of the metaheuristic algorithm within that space.
Here's how a contour plot of a search space is typically generated and interpreted in the context of metaheuristic techniques:
Objective Function: First, you need to have an objective function that defines the problem being optimized. The objective function takes the solution variables as inputs and produces a scalar value, representing the quality or fitness of the solution.
Solution Variables: Determine the range or bounds of the solution variables. For example, in an optimization problem involving two variables, x and y, you may specify their ranges, such as -10 ≤ x ≤ 10 and -5 ≤ y ≤ 5.
Define a Grid: Create a grid or mesh of points in the solution variable space, covering the specified ranges. The resolution of the grid depends on the desired level of detail in the contour plot.
Objective Function Evaluation: Evaluate the objective function for each point in the grid. The resulting fitness values determine the contours in the plot.
Contour Plot Generation: Plot the points from the grid on a two-dimensional graph, with the x and y variables representing the coordinates. Each point's fitness value is indicated by the contour lines or color shading, showing regions of similar fitness.
Interpretation: Analyze the contour plot to gain insights into the search space. Key interpretations include: Fitness Landscape: The contour lines or color gradients represent the fitness landscape, indicating areas of higher or lower fitness. Steeper gradients may indicate sharper optima or more challenging regions for optimization. Optimal Solutions: Peaks or plateaus in the contour plot represent optimal or near-optimal solutions. The number and locations of these peaks can provide insights into the problem's complexity and multiple optima. Connectivity: Contour lines that connect across the search space indicate how regions of different fitness levels are interconnected. It helps to identify potential paths for exploration and movement of solutions during the metaheuristic optimization process. Search Trajectories: By overlaying the contour plot with the trajectory of the metaheuristic algorithm, you can visualize how it explores and moves through the search space, and how it converges or diverges towards optimal solutions.
The contour plot of the search space can provide valuable information about the problem landscape, guide the selection and fine-tuning of metaheuristic techniques, and aid in the interpretation of optimization results. It allows researchers to gain insights into the behavior and performance of the algorithm within the problem space, facilitating informed decision-making during the optimization process.
For scalable functions, it is useful to plot function values for two variables (within the search range). This will give us an idea of whether the search space is unimodal or multimodal. If you will take the projection of the 3d plot it will give you a contour plot. It can be done in MATLAB easily.