sparsehash: sparsehash (An extremely memory-efficient hash_map implementation)
sparsehash:
sparsehash: The SparseHash library contains several hashmap  implementations,
sparsehash: including  implementations  that  optimize for space or speed.
sparsehash: 
sparsehash:
sparsehash:
sparsehash:
sparsehash:
sparsehash:
sparsehash: