Good guess, but in this case the size of the vector container was always constant - 4 elements (even if only 2 or 3 of them were ever used). Presumably what ma

Good guess, but in this case the size of the vector container was always constant - 4 elements (even if only 2 or 3 of them were ever used). Presumably what made it faster was being able to unroll loops? (only a guess, never looked at the disassembly) -- so instead of 0 to x on each vector element, it would loop through 0 to 2 and could optimize around this for each function.