Ask Yourself: What search algorithm should be used for this AutoStow session?The recursive-based iterative algorithm is applicable only when stowing the entire vessel. When using AutoStow to stow individual bays the solution will revert to the recursive algorithm, option 1.
Sequence of events to generate loading plans using the recursive-based iterative algorithm:
Sort all projected positions for each stowage group by tier from top to bottom and stack from centre to side.
Sort all containers by stowage group in the descending order of weight.
Create and cache an initial solution by sequentially assigning containers to projections for each stowage group. This initial solution is entirely weight driven and should be free of weight inversion and therefore have low values for weight related penalties. However, this plan usually has very high values for non-weight related penalties such as CHE gantry moves and yard shifts. This initial solution is just a starting point, a bench mark of the iterative algorithm. The initial stowage plan for each stow group is replaced with a more compromised solution when the algorithm loops through the stowage groups for the first time as described in point 4.
Sort all stowage groups into a list in the descending order of their total penalties based on the initial solution and take the first and highest scoring stowage group as the current group to work on.
From the currently working stow group revert all container position assignments and create a new solution by refilling all projected slots using the move time order and recursive algorithm. This gives AutoStow a wide range of candidate containers to choose for each projection.
Even though the assignments between containers and projections of other stowage groups are not affected when one stowage group is explored, the disutility of any single association may change when the solution is modified for working on stowage group because the projections and containers in one stowage group may interweave with those in other groups, both physically (stacking relationship) and chronologically (moving time).
With respect to penalty scoring, compare the current solution results to the previous. If this current solution is equal to or lower than the total penalty of the previous then progress to step 7 otherwise a) replace the original solution with the current one and b) take the next stowage group and return to step 4.
Upon completion of the initial stowage plan and if weight inversion is heavily penalized then remove weight inversions for each weight inverted stack. This is completed by assessing containers of the same stow factor within these stacks and swapping their positions as efficiently as possible within the stack to eliminate the weight inversion.
All projections can be divided into the following sets:
Projections prior to the current stowage group include all projections whose move times are prior to the first projection's move time of the current stowage group. The disutility of container assignment for any projection in this set would not change when you explore the current stowage group.
Projections following the working on stowage group these include all projections (but excludes the first projection) whose move times are after the last projection's move time of the current stowage group. The disutility of container assignment for any projection in this set needs to be re-scored when the solution for the working on stowage group changes.
Projections within the current stowage group, which include all projections chronologically interwoven with the current stowage group irrespective of belonging to the current stowage group or not which need to be included and re-scored in the modified recursive algorithm.
The major difference between the two algorithms is that the recursive-based iterative algorithm has a higher forward-looking visibility with the same search depth parameter, CFGSDP (on page 1).
Ask Yourself: What search algorithm should be used for this AutoStow session?