 Thus if a set "A" is decidable then "A" is reducible to any set "B" under any of the strong reducibility relations listed above, even if "A" is not polynomial-time or exponential-time decidable.This is acceptable in the study of recursion theory, which is interested in theoretical computability, but it is not reasonable for computational complexity theory, which studies which sets can be decided under certain asymptotical resource bounds.The most common reducibility in computational complexity theory is polynomial-time reducibility; a set "A" is polynomial-time reducible to a set "B" if there is a polynomial-time function "f" such that for every "n", "n" is in "A" if and only if "f"("n") is in "B".