scala - When is it appropriate to use a TrieMap? -

i have been reading posts , wondering if can present situation on when triemap preferable using hashmap.

so architecture decision should motivate use of triemap?

as per documentation. it's mutable collection can safely used in multithreading applications.

a concurrent hash-trie or triemap concurrent thread-safe lock-free implementation of hash array mapped trie. used implement concurrent map abstraction. has particularly scalable concurrent insert , remove operations , memory-efficient. supports o(1), atomic, lock-free snapshots used implement linearizable lock-free size, iterator , clear operations. cost of evaluating (lazy) snapshot distributed across subsequent updates, making snapshot evaluation horizontally scalable.

for details, see: http://lampwww.epfl.ch/~prokopec/ctries-snapshot.pdf

also has nice api caching. example have calculate factorials of different number , re-use results.

  object o {      val factorialscache = new triemap[int, int]()      def factorial(num: int) = ??? // heavy operations     def doworkwithfuctorial(num: int) = {       val factres = factorialscache.getorelseupdate(num, {         // not want invoke         factorial(num)            // function executed if there no records in map such key       })       // start work `withfactres`       factres     }   } 

pay attention - function above use global state (cache) write operations, it's absolutely safe use in concurrent threads. you'll not loose data.