Experiences with Concurrent Hash Map Libraries

• parallel-hashmap

  31 2,316 7.8 C++

  A family of header-only, very fast and memory-friendly hashmap and btree containers.

I'm the author of parallel-hashmap. There are ways to do what you suggest either lock-free, or with minimal locking. If you have a test program for your use case I'd be happy to adapt it for using phmap.

• libcuckoo

  4 1,538 3.5 C++

  A high-performance, concurrent hash table

  

libcuckoo replaced junction as my concurrent hash map and allowed me to get rid of my pointer longevity management and I saw no decrease in performance. No commits in over a year I think the author of parallel-hashmap made a good point here where he pointed out that it's only worth trying the more experimental hash maps like junction or growt when hash map access is actually the bottleneck. In my case the performance of libcuckoo was not a bottleneck, so I saw no difference in performance compared to the use of junction.

• InfluxDB

  www.influxdata.com sponsored

  Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.

  

• Folly

  90 27,072 9.8 C++

  An open-source C++ library developed and used at Facebook.

  

folly's AtomicHashMap requires knowing the approximate number of elements up-front and the space for erased elements can never be reclaimed. This doesn't work well for our application.

• growt

  2 98 2.7 C++

  This is a header only library offering a variety of dynamically growing concurrent hash tables. That all work by dynamically migrating the current table once it gets too full.

growt shows impressive benchmark results in this paper compared to folly, TBB, junction, and libcuckoo. However, it was not in good shape to be used as a production dependency. I had several issues and compilation errors here, here, and here.

• junction

  1 1,365 0.0 C++

  Concurrent data structures in C++

junction has a very impressive performance benchmark here. Initially it worked for my application, but I ran into some issues: Only raw pointers are supported as either keys or values. This means I am responsible for memory management and it was a pain. junction's required dependency "turf" causes linker errors when compiling with -fsanitize=address because there are symbol name collisions. Every thread that accesses the hash map must periodically call an update function or memory will be leaked. No commits in over three years, GitHub issues aren't getting any attention. The author said it's experimental and he doesn't want it to become more popular

• FASTER

  8 6,199 7.2 C#

  Fast persistent recoverable log and key-value store + cache, in C# and C++.

  

you could use fasterkv https://github.com/microsoft/FASTER

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