Unordered_set with structure

[yofufufufu]

Hello, I'm new to this library. I wonder what should I do if I want to use something like stdgpu::unordered_set<thrust::pair<int, int>> or stdgpu::unordered_set<myStruct> ? Because when I try to use stdgpu::unordered_set<thrust::pair<int, int>>::createDeviceObject(n), the error occurred:

/usr/local/include/c++/9.5.0/type_traits(2378): error: class "std::enable_if<false, thrust::pair<int, int>>" has no member "type"
          detected during:
            instantiation of type "std::enable_if_t<false, thrust::pair<int, int>>" 

[stotko]

stdgpu::unordered_set has similar requirements than std::unordered_set. In particular, this means that stdgpu::hash must be specialized for the desired type and that stdgpu::equal must be able to use the type's operator==() function. For your two examples, this means:

• thrust::pair<int, int>: Here, operator==() is already defined and, hence, stdgpu::equal will already work. However, stdgpu::hash is not specialized which results in the error message you have received. Though, the message is unfortunately not that informative at the moment and could be improved to make this fact clearer.
• myStruct: Here, you would have to define both functions to make this work.

[yofufufufu]

Thanks for your reply! Now I can use stdgpu::unordered_set<thrust::pair<int, int>> with custom hash function.

[stotko]

Closing this issue as the issue has been resolved and further improvements to the less informative error message can be done in the future.