Approximating the satisfaibility threshold for random k-XOR formulas

Nadia Creignou , Hervé Daudé , Olivier Dubois (1)

1 SYSDEF - Systèmes d'aide à la décision et à la formation

In this paper we study random linear systems with $k > 3$ variables per equation over the finite field GF(2), or equivalently k-XOR-CNF formulas. In a previous paper Creignou and Daudé proved that there exists a phase transition exhibiting a sharp threshold, for the consistency (satisfiability) of such systems (formulas). The control parameter for this transition is the ratio of the number of equations to the number of variables, and the scale for which the transition occurs remains somewhat elusive. In this paper we establish, for any $k > 3$, non-trivial lower and upper estimates of the value of the control ratio for which the phase transition occurs. For $k=3$ we get 0.89 and 0.93, respectively. Moreover, we give experimental results for $k=3$ suggesting that the critical ratio is about 0.92. Our estimates are clearly close to the critical ratio.

Domaines: Informatique [cs]

Nadia Creignou, Hervé Daudé, Olivier Dubois. Approximating the satisfaibility threshold for random k-XOR formulas. Combinatorics, Probability and Computing, 2003, 12 (2), pp.113-126. ⟨10.1017/S0963548302005552⟩. ⟨hal-01185763⟩