Update README.md

README.md

@@ -98,7 +98,8 @@ The full types with template parameters can be found in the [parallel_hashmap/ph
 
 - The default hash framework is std::hash, not absl::Hash. However, if you prefer the default to be the Abseil hash framework, include the Abseil headers before `phmap.h` and define the preprocessor macro `PHMAP_USE_ABSL_HASHEQ`.
 - The `erase(iterator)` and `erase(const_iterator)` both return an iterator to the element following the removed element, as does the std::unordered_map. A non-standard `void _erase(iterator)` is provided in case the return value is not needed.
-- No new types, such as `absl::string_view`, are provided. `std::string_view` is supported by phmap tables when built with a stdlib providing this type.
+- No new types, such as `absl::string_view`, are provided. All types with a `std::hash<>` implementation are supported by phmap tables (including `std::string_view` of course if your compiler provides it).
+- The Abseil hash tables internally randomize a hash seed, so that the table iteration order is non-deterministic. This can be useful to pervent *Denial Of Service*  attacks when a hash table is used for a customer facing web service, but it can make debugging more difficult. The *phmap* hashmaps by default do **not** implement this randomization, but it can be enabled by adding `#define PHMAP_NON_DETERMINISTIC 1` before including the header `phmap.h` (as is done in raw_hash_set_test.cc).
 
 
 ## Memory usage