  AmbSAT (or AmoebaSAT) is a biologically-inspired stochastic local search
(SLS) solver to explore solutions to the Boolean satisfiability problem (SAT).
AmbSAT updates multiple variables in parallel at every iteration step, and thus
AmbSAT can find solutions with a fewer number of iteration steps than some
other conventional SLS solvers for a specific set of SAT instances. However,
the parallelism of AmbSAT is not compatible with general-purpose
microprocessors in that many clock cycles are required to execute each
iteration; thus, AmbSAT requires special hardware that can exploit the
parallelism of AmbSAT to quickly find solutions. In this paper, we propose a
circuit model (hardware-friendly algorithm) that explores solutions to SAT in a
similar way to AmbSAT, which we call circuit-level AmbSAT (CL-AmbSAT). We
conducted numerical simulation to evaluate the search performance of CL-AmbSAT
for a set of randomly generated SAT instances that was designed to estimate the
scalability of our approach. Simulation results showed that CL-AmbSAT finds
solutions with a fewer iteration number than a powerful SLS solver, ProbSAT,
and outperforms even AmbSAT. Since CL-AmbSAT uses simple combinational logic to
update variables, CL-AmbSAT can be easily implemented in various hardware.
