Thread-safe LRU Cache

A set of header-only C++ classes providing thread-safe LRU caches. Uses Intel's tbb::concurrent_hash_map.

• ThreadSafeLRUCache is a single tbb::concurrent_hash_map with attached LRU list.
• ThreadSafeScalableCache is a cache object built from a collection of ThreadSafeLRUCache objects, with items distributed by key hash. This allows it to serve a high rate of evictions/inserts without significant lock contention.
• ThreadSafeStringKey is a reference-counting string object with a memoized hash value. This is recommended as a key object for the above two containers.

For indicative benchmarks to help with container selection, see the benchmarks page on the wiki.