Rules 2021
Update 20210420
Categories
The 2021 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 2021 competition, the order/degree pairs (n, d) = (40, 5), (432, 12), (512, 18), (1024, 5), (3602, 24), (65536, 64), (158976, 10), (100000, 128) are featured. Note that the graphs can be nonregular.

HostSwitch Graph Category

Find a hostswitch graph with minimum hosttohost diameter (hdiameter) over all undirected hostswitch graphs with the number of host vertices = n and radix ≤ r. If two or more hostswitch graphs take the minimum hdiameter, a hostswitch graph with minimum hosttohost average shortest path length (hASPL) over all the hostswitch graphs with the minimum hdiameter should be found. For the 2021 competition, the order/radix pairs (n, r) = (32, 4), (80, 6), (128, 24), (432, 12), (1281, 21), (3800, 30), (1024, 5), (1024, 10), (4608, 36), (8208, 48), (10000, 10), (10000, 100), (65536, 64) are featured. Note that the hostswitch graphs can be nonregular. You can use many switch vertices as you want on the hostswitch graph.
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 (h)diameter, and with the smallest (h)average shortest path length (ASPL) among those with the same (h)diameter, for each order/degree(radix) pair. Formally speaking, we calculate score = 1000000k + l, where k is the (h)diameter and l is the (h)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 (h)ASPL gap over all the order/degree(radix) pairs. The (h)ASPL gap is calculated as gap = l − L, where l is the (h)ASPL of the graph and L is the lower bound of l calculated as in [Cerf 1974] for general graphs and as in [Yasudo,2019] for hostswitch graphs.
Only those graphs that complies with the featured order/degree(radix) 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 20210726) and the open submission period (after 20210726). At the beginning, solutions accepted by 20210725 23:59 UTC are reviewed and publicated on 20190726. 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 20211011 23:59 UTC. The last day will be treated as the same week as 20211004.
The firsttofile rule applies to those graphs with the same (h)diameter and (h)ASPL. For each order/degree(radix) pair, if two or more graphs have the same diameter and the same (h)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 submitted 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

20210427: Closed submission period starts

20210726: Open submission period starts

20211011: Submission period ends (deadline 20211011 23:59:59 UTC)

20211018: Awards notification

20211123(tentative): Workshop in CANDAR'21