Solved by tom in post #2 
              
              
                Hi Andrew, 
yes, in a way they’re related. 
Bincount seems to eventually reduce to kernelHistogram1D in SummaryOps.cu. That uses atomicAdds, which lead to the non-determinism and are actually of poor performance when many threads want to write to the same memory location. 
I think one (hacky) way to…