fast here means compared to a naive implementation. They use a lot of optimization and heuristics.
What would be a O(2^256) problem? A boolean formula with 256 binary variables? In many cases those can be broken down to independent smaller formulas which are easier to solve, in which case a solver might be quite fast on it, yes. But something that provably does not reduce to a smaller complexity would still take forever, I guess. Corrections welcome.
What would be a O(2^256) problem? A boolean formula with 256 binary variables? In many cases those can be broken down to independent smaller formulas which are easier to solve, in which case a solver might be quite fast on it, yes. But something that provably does not reduce to a smaller complexity would still take forever, I guess. Corrections welcome.