For my own thing I used neither Estrin's nor Horner's. I profiled a bunch of equivalent parse trees and then zeroed on one that was performing well on the targe

For my own thing I used neither Estrin's nor Horner's. I profiled a bunch of equivalent parse trees and then zeroed on one that was performing well on the target m/c. You may not need communication though. As lng as it decomposes into mutually independent subtrees the compiler can exploit that to generate better code.