The fastest thing I would think is to process 255 vectors at a time, using an accumulation vector with the k-th byte in the vector representing the # of evens s

The fastest thing I would think is to process 255 vectors at a time, using an accumulation vector with the k-th byte in the vector representing the # of evens seen for the k-th byte of the vectors in that 255-vector chunk. But, I don’t know how to make autovectorization do that. I could only do that with intrinsics.