 Simultaneous exponentiation by squaring

Several powers with one nonnegative exponent can share a single exponent-halving loop. For bases $a_j$, maintain accumulators $p_j$, current bases $u_j$ and a remaining exponent $k$, with loop invariants $p_j{u}_j^k=a_j^n$. For an odd $k$, multiply every accumulator by its current base; square every current base and halve $k$. The equalities are preserved in parallel, and the nonnegative loop variant $k$ strictly decreases. For a fixed number of bases this uses $O(\log (n+1))$ arithmetic operations and one loop, while keeping each base in the intended numeric type.