Single-call Polyak-Type Extragradient Methods for Monotone Root-Finding Problems

We propose a single-call variant of Polyak extragradient, termed SPolyakEG, by recycling the previous extrapolation operator evaluation. Under a delayed critical condition, we establish that SPolyakEG achieves an $O(1\mathrm{/}K)$ residual convergence rate for monotone operators and linear convergence under strong monotonicity. Compared with PolyakEG, SPolyakEG reduces the number of operator evaluations from two to one per iteration.