Aguri tries, which are bounded-sized radix trees with an LRU aggregation rule of joining sibling nodes.
The motivating use case is tracking metrics for IP addresses. You insert individual IP addresses into the tree, and when the tree fills, it starts rolling nodes for /32s into /31s, /30s, &c. Eventually, you get a picture of ranges of IP addresses in the data. That's neat, because, of course, IP packets themselves don't tell you anything about what subnets their IP addresses belong to.
The goofy thing I've done with them is apply them to memory addresses, so that I can collect individual pointers and bubble them up into allocation ranges, without instrumenting allocators.
The motivating use case is tracking metrics for IP addresses. You insert individual IP addresses into the tree, and when the tree fills, it starts rolling nodes for /32s into /31s, /30s, &c. Eventually, you get a picture of ranges of IP addresses in the data. That's neat, because, of course, IP packets themselves don't tell you anything about what subnets their IP addresses belong to.
The goofy thing I've done with them is apply them to memory addresses, so that I can collect individual pointers and bubble them up into allocation ranges, without instrumenting allocators.