Travel Cache & Maintenance

ProTrack Warehouse uses a method of caching in order to optimize performance when computing shortest-path travel calculations. A dual-stage caching methodology has been implemented as of ProTrack Warehouse version 7.3, which first caches node-to-node travel, and then caches travel routes between unique pairs of locations. Once both stages are completed for a pair of locations, that particular pairing is considered to be “fully cached.”

ProTrack Warehouse utilizes two methods in order to build the cache. First a node-to-node cache is ALWAYS primed (ahead of the time that it is actually needed during standards calculation). Additionally, some degree of location-to-location cache can be primed. The process of building these two pre-caches is referred to as “priming the cache.” Secondly, as travel time is calculated between two locations, the shortest path is cached “on-the-fly” for location pairing without a pre-existing cache.

Priming the NodeCache and LocationCache - Overview

Node caching and location caching can both be independently “primed” ahead of time before standards are being calculated. This results in a huge performance gain when calculating standards involving travel.

“Priming” the cache means that there will be a “history” generated of travel combinations between two locations and nodes before travel actually occurs between those locations in the live production environment.

The priming processes of both node cache and location cache are handled independently. It is required that Node Cache ALWAYS be primed; location priming is considered optional. However in environments with pre-download assignments, location priming is recommended.

Priming the Node and Location Caches

As mentioned briefly earlier, the Caching screen is used to create and delete the Node and Location Caches. Click on 'Caching' and the Node and Location Caching screen appears.


^{Fig.1 Maintain Facility Layout - Caching}

Contained in the left box are all options for generating Node Cache. The user must specify the following:

1. Generate cache between nodes on the same floor only: (Y/N). Default is Yes.
2. Select the floor to generate cache for: (Default: All Floors).
3. Only generate cache for combinations of nodes that are directly connected to locations: (Y/N): Default is Yes.
4. Delete existing cache first (N/Y). Default is Yes.

Clicking  creates an entry in Scheduled Requests. The progress of the task can be monitored on the Monitor > Scheduled Request screen.


^{Fig.2 Maintain Facility Layout - Node Caching}
 

Contained in the right box are all options for generating Location Cache. The options that the user must specify are similar to those for Node Cache:

1. Generate cache between locations on the same floor only: (Y/N). Default is Yes.
2. Select the floor to generate cache for: (Default: All Floors).
3. Select the number of combinations, per location to cache: Default is 100. This generates cache between each location and it's closest 100 locations.
4. Delete existing cache first (N/Y). Default is Yes.

Clicking  creates an entry in Scheduled Requests. The progress of the task can be monitored on the Monitor > Scheduled Request screen.


^{Fig.3 Maintain Facility Layout - Location Caching}

Maintaining Node and Location Caches

Whether or not the two caches need to be recalculated depends on what was changed. Here are the different change scenarios and requirements:

1. Location is added to a pre-existing Segment: no change to either cache is required.

2. Location is added to a newly imported Segment: additional node cache may be required. It is not necessary to delete existing node cache, simply regenerate it for the affected floor and automatically create any node cache that is missing due to the recent import of Segments.

   Info

   • This additional cache will only be required if option 3 in the Node Cache generation was set to ‘Yes’. If it was set to ‘No’, then all possible Node Cachings would have been generated in the first place so nothing could be missing.
3. Location is moved or deleted: location cache must be deleted.
   1. Any changes that result in regenerating Nodes: both caches must be deleted for the affected floor(s). This may result from an Aisle Path or Travel Path being added or deleted.
4. Additions, deletions, or modifications to Segments have no direct impact on either cache.