Rules 2019
Update 20190729
Categories
The 2019 competition consists of two categories:

General Graph Category

Find a graph with minimum diameter over all undirected graphs with the number of vertices = n and degree ≤ d. If two or more graphs take the minimum diameter, a graph with minimum average shortest path length (ASPL) over all the graphs with the minimum diameter should be found. For the 2019 competition, the order/degree pairs (n, d) = (50, 4), (512, 4), (512, 6), (1024, 4), (1726, 30), (4855, 15), (9344, 6), (65536, 6), (100000, 8), (1000000, 16), (1000000, 32) are featured. Note that the graphs can be nonregular.

Grid Graph Category

Do the same as above, but on a w × h grid in a twodimensional Euclidean space, keeping the lengths of the edges ≤ r in Manhattan distance. Here a "grid" implies that (1) the vertices are located at integer coordinates but are not necessarily connected to its adjacent vertices; and (2) the edges must not run diagonally while being allowed to change its direction at the grid points. For the 2019 competition, the order/degree/length pairs (w×h, d, r) = (5×5, 4, 2), (5×10, 4, 2), (10×10, 4, 2), (10×10, 6, 3), (10×10, 8, 4), (20×20, 4, 2), (20×20, 6, 3), (20×20, 8, 4), (100×100, 4, 2), (100×100, 6, 3), (100×100, 8, 4) are featured.
Awards
Each category has two awards:

Widest Improvement Award

The widest improvement award goes to the authors who find the largest number of best solutions. The best solution means a graph with the smallest diameter, and with the smallest average shortest path length (ASPL) among those with the same diameter, for each order/degree(/length) pair. Formally speaking, we calculate score = 1000000k + l, where k is the diameter and l is the ASPL, and pick the graph with the lowest score as the best solution.

Deepest Improvement Award

The deepest improvement award goes to the authors who achieve the smallest ASPL gap over all the order/degree(/length) pairs. The ASPL gap is calculated as gap = l − L, where l is the ASPL of the graph and L is the lower bound of l calculated as in [Cerf 1974] for general graphs and [Nakano 2016] for grid graphs.
Only those graphs that complies with the featured order/degree(/length) pair will be nominated for the awards. However, we also accept nonfeatured graphs and make them exhibited on the ranking page. We encourage you to submit your results no matter if featured or not.
Schedule and tiebreaking rule
The competition goes through two phases: the closed submission period (before 20190721) and the open submission period (after 20190722). At the beginning, solutions accepted by 20190721 23:59 UTC are reviewed and publicated on 20190722. Afterwards, solutions accepted within a week are reviewed and publicated every Monday. Note that a week begins at Monday 00:00 UTC and ends at Sunday 23:59 UTC. At the end, solutions will be accepted until 20191014 23:59 UTC. The last day will be treated as the same week as 20191007.
The firsttofile rule applies to those graphs with the same diameter and ASPL. For each order/degree(/length) pair, if two or more graphs have the same diameter and the same ASPL, only those graphs publicated at the earliest time will be nominated for the awards. If there are two or more such graphs publicated at the same time, all of them will be nominated.
Publication
When publicated, the submitted graph file will be made available for downloads. The submitetd graphs will also be publicated later at Grpah Bank, which is an open database of interesting graphs developed by the Graph Golf team.
Important dates

20190429 20190513: Closed submission period starts

20190722: Open submission period starts

20191014: Submission period ends (deadline 20191014 23:59:59 UTC)

20191021: Awards notification

20191126 (tentative): Workshop in CANDAR'19