GECCO 2021
Competition on Niching Methods for Multimodal Optimization

Competition on Niching Methods for Multimodal Optimization

Submission deadline: 25 June 2021 (Final)

The aim of the competition is to provide a common platform that encourages fair and easy comparisons across different niching algorithms. The competition allows participants to run their own niching algorithms on 20 benchmark multimodal functions with different characteristics and levels of difficulty. Researchers are welcome to evaluate their niching algorithms using this benchmark suite, and report the results by submitting a paper to the main tracks of GECCO (i.e., submitting via the online submission system of GECCO'2021).

The GECCO 2021 competition on Niching Methods for Multimodal Optimization is similar to the GECCO 2020 competition. It largely follows the procedures of the 2013/2015 CEC niching competitions. The set of problems is the same, and the interface is not changed. However, we modify the submission report format (the files that contain the best solutions found within a run) slightly by adding some new information. The participants have to follow the format described in the SUBMISSION section bellow.

The new formats includes information for the final solution set found by the algorithm for each execution run. It includes the search space coordinates of a reported solution, its fitness value and information on the resources used until this solution has been found (number of used fitness evaluations, and the time). Time measurements are not essential but rather needed for checking that the generated order is correct. It may also be employed for rough comparison of the overall time (wall time) the algorithms need for generating a solution set, but this is of no importance for this issue of the competition.

The other important change concerns the performance criteria. As before, we fix the maximum amount of evaluations per run and problem and count the number of detected peaks as our first measure. This is also known as recall in information retrieval, or sensitivity in binary classification. Recall is defined as the number of successfully detected items (out of the set of relevant items), divided by the number of relevant items.

Additionally, we will also look at 2 more measures, namely the static F1 measure (after the budget has been used up), and the (dynamic) F1 measure integral. The F1 measure is usually understood as the product of precision and recall. Precision is meant as the fraction of relevant detected items compared to the overall number of detected items, in our case this is the number of detected peaks divided by the number of solutions in the report ("best") file. That is, the higher the number of duplicates or non-optimal solutions in the report, the worse the computed performance indicator gets. Ideally, the report file shall provide all sought peaks and only these, which would result in an F1 value of 1 (as both recall and precision would be 1).

The static F1 measure uses the whole report file and computes the F1 measures of complete runs, and these are then averaged over the number of runs and problems. The 3rd measure is more fine-grained and also looks at the time (in function evaluation counts) when solutions are detected. Therefore, track the report file line by line and compute the F1 value for each point in time when a new solution (line) is written, using all the information that is available up to that point. Thus we compute the F1 value "up to that time", and doing that for each step results in a curve. The F1 measure integral is the area under-the-curve (AUC), divided by the maximum number of function evaluations allowed for that specific problem. It is therefore also bounded by 1.

In the case if you cannot virtually attend GECCO 2021, we encourage you to submit a short report about your algorithm and results. You can submit the report directly to the special session organizer Michael Epitropakis, in order to be counted in the competition. More specifically, the authors are expected to submit the solutions found in this report, in order for us to validate the results. Please follow the format described in the SUBMISSION section bellow.

Submission files format (2018 format):

Each participant can submit more that one entries (algorithms). For each entry (algorithm) the participant has to provide a compressed folder, named preferably as the algorithm's name (eg DEnrand.zip), with the following ASCII text files. For each benchmark problem (20 benchmarks) and for each independent execution run (50 runs), the participant has to save the final solution set of the execution in a separate text file named for example: for benchmark 1, execution run 1 the filename should be: problem001run001.dat. A total of 50 x 20 = 1000 ASCII text files have to be submitted (compressed as stated above). Each text file should contain the final solution set that will be submitted to the organizers. Manual pre/post processing of the files is not allowed.

The basic format of each ASCII text file is:

Solution stands for the search space coordinates of a reported solution (tab or space separated), then we use the equal sign to mark that now the fitness values (only one in our case) follow. The "@" ends this block, and the last two columns stand for the number of used fitness evaluations until this solution has been found, and the time in milliseconds. As mentioned above, the latter is not essential but rather needed for checking that the generated order is correct. It may also be employed for rough comparison of the overall time (wall time) the algorithms need for generating a solution set, but this is of no importance for this issue of the competition.

In this competition, we have also added the action column (last column) that represents the action that has to be performed with this solution (Acceptable values: 0, 1, -1). We have defined three main actions (0/1/-1):

• Reset archive and add solution (0): This action deletes everything that has been reported in the current file and adds the current solution as the first solution in the archive.
• Add solution (1): This is the normal case where the reported solution is added in the archive.
• Delete solution (-1): In this case, we search through the archive and delete the reported solution. If the archive does not contain this solution, we do not take any action. Notice that the solutions are hashed by the following features: Solution (x1,x2,...,xd), fes, and time. As such, a solution will be removed only if the exact same solution is found within the archive.

Notice that, in case where the action column is not used in the submission files, we will assume that every row has action value of 1 (Add solution).