merge_sort

[ntrost57]

Does device wide merge_sort support in-place sorting (keys_input == keys_output and values_input == values_output)?
What about radix sort? I guess it does not support in-place sorting, but I could not find anything in the docs about it.

[jszuppe]

Unless, it's explicitly stated otherwise, input and output iterators must point to separate memory (separate ranges).

[ntrost57]

Thank you for your answer. Is radix_sort and/or merge_sort stable? I cannot find anything in the docs about it, however, in the tests, you are comparing to std::stable_sort.

[jszuppe]

Radix sort is stable. Merge sort is not.

[ntrost57]

Thank you very much! I have one more question:
Using zip_iterator to sort multiple values with the same key is straight forward. What about using zip_iterator with double buffers?

[jszuppe]

What about using zip_iterator with double buffers?

I don't think that's possible. double_buffer class template takes value type (T) not iterator type. I guess you may try modifying it to operate on iterators instead. You can always try to specialize it for zip_iterator.

[ntrost57]

I am not sure if that is possible, with integers zip_iterator has value_type tuple<int*,int*> but radix_sort_impl() requires value_type tuple<int, int>* for buffers. The integer arrays packed with zip_iterator are not necessarily continuous in memory.

[jszuppe]

Yes, right now it's not possible. It would require some changes to radix sort implementation (it's doable). Right now there are not plans to do them.