What is a good sorting algorithm on CUDA?

Question

I have an array of struct and I need to sort this array according to a property of the struct (N). The object looks like this:

 struct OBJ
 { 
   int N; //sort a         


        

Answer 1

What means "big" and "small" ?

By "big" I assume you mean something of >1M elements, while small --- small enough to actually fit in shared memory (probably <1K elements). If my understanding of "small" matches yours, I would try the following:

• Use only a single block to sort the array (it can be then a part of some bigger CUDA kernel)
• Bitonic sort is one of good appraches which can be adopted for parallel algorithm.

Some pages on bitonic sort:

• Bitonic sort (nice explanation, applet to visualise and java source which does not take too much space)
• Wikipedia (a bit too short explanation for my taste, but more source codes - some abstract language and Java)
• NVIDIA code Samples (A sample source in CUDA. I think it is a bit ovefocused on killing bank conflicts. I believe the simpler code may actually perform faster)

I once also implemented a bubble sort (lol!) for a single warp to sort arrays of 32 elements. Thanks to its simplicity it did not perform that bad actually. A well tuned bitonic sort will still perform faster though.