Simultaneous support for multi-word LL/SC and bounded tags with optimal space

Construct an LL/SC implementation that simultaneously supports multi-word LL/SC and avoids augmenting LL/SC values with bounded tags stored in CAS objects, while retaining the stated space bounds of the randomized implementation.

Background

The paper presents a randomized implementation of multiple LL/SC objects using FAID and CAS objects. Its construction achieves favorable asymptotic step and space complexity, but requires augmenting LL/SC values with small bounded tags stored in CAS objects and does not support multi-word LL/SC. The authors explicitly identify achieving both of those properties simultaneously without sacrificing the construction’s space bounds as unresolved.

References

Achieving these properties simultaneously with our space bounds remains an important open problem.

— Efficient Randomized LL/SC that Preserves History Independence  (2608.12946 - Bencivenga et al., 13 Aug 2026) in Section Conclusion

Other open problems include finding lower bounds on space complexity for deterministic or even randomized algorithms, as well as a general construction for inserting \CL{} operations into implementations using LL/SC while preserving their asymptotic space complexity.

— Efficient Randomized LL/SC that Preserves History Independence  (2608.12946 - Bencivenga et al., 13 Aug 2026) in Section Conclusion