Can cub::DeviceSegmentedSort::SortKeys support user-defined compare functors?

[zlwu92]

Let's say I have a device array (use cudaMalloc), int* nodelist[], and another device array (use cudaMalloc), int* weight[]...

I want to use cub::DeviceSegmentedSort::SortKeys to sort nodeslit[], but I want to define a compare functor that need to use the weight[]..., can I do this?

[gevtushenko]

Hello @zlwu92! Unfortunately, our segmented sort facilities do not support comparison operators. That's because segmented sort relies on radix sort in the cases of large segments and a small number of segments (radix sort is not comparison based).

Nonetheless, if your weights are of arithmetic type, you could use cub::DeviceSegmentedSort::SortPairs with weight as keys and nodelist as values. In this case, values will be permuted the same way as keys.

In case you need a non-trivial comparison operator, you could use cub::DeviceMergeSort::SortPairs if you embed the segment id into the most significant part of your keys.