Dear Boost, CC: Howard, Jonathan for N3645 enhancements It has taken me far longer than I expected, however I believe that proposed boost::concurrent_unordered_map is ready for community feedback, with its unit test suite passing all green on the thread sanitiser and 92% coverage including exception safety tests. The main documentation page with the API and a lengthy explanation of the caveats in this design can be viewed at https://ci.nedprod.com/view/Boost%20Thread-Expected-Permit/job/Boost.S pinlock%20Test%20Linux%20GCC%204.8/doxygen/classboost_1_1spinlock_1_1c oncurrent__unordered__map.html Performance improves linearly to CPU cores at a slope of about 0.9. I only have four core hardware available to me, if someone could tell me how it scales to eight cores or more I would be very interested. Source code is at https://github.com/ned14/boost.spinlock. Tested on GCC 4.8, clang 3.4 and VS2013. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/