fastmap

The fastmap package provides fast key-value maps, stacks, and queues for R. Unlike R’s standard environment-based maps, fastmap avoids memory leaks and performance degradation that occur when using large numbers of keys.

Standard R environments intern every key as a symbol in R’s global symbol table, which is never garbage-collected and slows down all GC operations as it grows. fastmap stores keys as C++ strings instead, preventing memory leaks and maintaining consistent performance even with millions of random keys. This makes it suitable for long-running processes or applications that use dynamically-generated keys.