This page documents the current status of my quest for 2LBB Busy Beavers.
The table below lists the search results for square grids for which a complete exhaustive search has been carried out. The meaning of the columns is as follows:
|Size||#Programs||#Hangs Detected||#Hangs Assumed||Max Run Length||Cut-off Run Length||Search Time|
For 6×6 not all hangs are automatically detected yet. This could theoretically mean that one of the programs that is assumed to be hanging might actually terminate. However, all these programs run for more than 100 million steps. Given that this is five orders of magnitude longer than the run length of the current Champion, 573, it is unlikely that any of these programs terminate. Nevertheless, until the hang detection automatically detects all hangs, the Champion is not yet the Busy Beaver.
For the 7×7 grid an exhaustive search has been completed with a cut-off limit of ten million steps. This search discovered the program in Figure 1 which takes 9607923 steps to complete. This is the current 7×7 Champion. As its run length is very close to the cut-off limit, it is highly unlikely that it is the Busy Beaver for the 7×7 grid.