in this paper i discuss putnam’s view on time and the special theory of relativity. i first locate putnam’s philosophical approach within a more general framework, essentially making reference to sellars’ distinction between the scientific image and the manifest image of the world. i then reconstruct putnam’s argument in favour of the reality of the future and the determinateness of truth-value...

nowadays, social networks play a key role in the study of sociology, socialpsychology and sociology. social network facebook has turned into a virtualsystem covering more than 900 million people around the world. in islamicrevolution of iran as a world revolution, universal definition, it can use as anew possibility. this paper will identify the capabilities and challenges withusing facebook. p...

We prove an exponential lower bound for tree-like Cutting Planes refutations of a set of clauses which has polynomial size resolution refutations. This implies an exponential separation between tree-like and dag-like proofs for both CuttingPlanes and resolution; in both cases only superpolynomial separations were known before [30, 20, 10]. In order to prove this, we extend the lower bounds on t...

The area of Propositional Satisfiability (SAT) has been the subject of intensive research in recent years, with significant theoretical and practical contributions. From a practical perspective, a large number of very effective SAT solvers have recently been proposed, most of which based on improvements made to the original Davis-Putnam-Logemann-Loveland (DPLL) backtrack search SAT algorithm. T...

This paper proposes a new algorithm for solving the Boolean satisfiability (SAT) problem. On the basis of this algorithm a software/reconfigurable hardware SAT solver was designed, implemented and compared to a similar realization of the Davis-Putnam-like method. The satisfier suggested uses an application-specific approach, thus an instancespecific hardware compilation is completely avoided.

We present DPVIS, a Java tool to visualize the structure of SAT instances and runs of the DPLL (Davis-Putnam-Logemann-Loveland) procedure. DPVIS uses advanced graph layout algorithms to display the problem’s internal structure arising from its variable dependency (interaction) graph. DPVIS is also able to generate animations showing the dynamic change of a problem’s structure during a typical D...

At some point there was the Davis-Putnam-Logemann-Loveland (DPLL) algorithm [6]. Forty five years later, research on Boolean satisfiability (SAT) is still ceaselessly generating even better SAT solvers capable of handling even larger SAT instances. Remarkably, the majority of these tools still bear the hallmark of the DPLL algorithm. In sync with the availability of progressively stronger SAT s...

The paper studies new unit propagation based heuristics for Davis-Putnam-Loveland (DPL) procedure. These are the novel combinations of unit propagation and the usual "MaximumOccurrences in clauses of Minimum Size" heuristics. Based on the experimental evaluations of di erent alternatives a new simple unit propagation based heuristic is put forward. This compares favorably with the heuristics em...

A decision procedure for propositional logic is presented. This procedure is based on the Davis-Putnam method. Propositional formulas are initially converted to negational normal form. This procedure determines whether a formula is valid or not by making validity-preserving transformations of fragments of the formula. At every iteration, a variable whose splitting leads to a minimal size of the...

We investigate iterated schemata whose syntax integrates arithmetic parameters, indexed propositional variables (e.g. Pi), and iterated conjunctions/disjunctions (e.g. Vn i=1 Pi, where n is a parameter). Using this formalism gives us some extra information about the structure of the problem, which can be used in order to prove such a schema for all values of the parameters. The structure of the...