The tile cache is the place where tiles
whose lock counter has returned to 0 are stored. The tiles in the
cache are eligible for unloading if memory is needed for loading
new tiles.
The cache can be shared among several
layers, which means that loading a tile in a layer can cause that
tile to be unloaded in another layer.
The IlvDefaultTileCache class implements a cache
algorithm consisting of a simple LRU (Least Recently Used)
structure that unloads first the tiles that have been visited the
least recently.
You can, however, implement another
algorithm that will be more efficient with respect to the specific
nature of your application. Here are a few criteria you might take
into account when implementing a new backup cache algorithm.
- Unload first the tiles that require a larger number of pan or zoom operations to be reached from the current position.
- Unload first the tiles that have taken the longest to load.
- Unload first the tiles that contain the largest number of graphic objects.
An example of a simplified cache algorithm is given in Writing a new cache algorithm.