Escape from solutions stagnation. A Study on Ant System solving TSP

Nowadays, routing problems arise in different contexts of distribution of goods, transportation of commodities and people. Routing problems deals with traveling along a given network in an optimal way. One of the major goals in optimization, including optimization of routing problems, is to reduce the time of stagnation by finding an exit state. The current work is a study about the ability of ants to escape from solution stagnation on a particular routing problem, the Traveling Salesman Problem.

Opening a Non-exit State

This article presents the passport policy of communist Poland, from the late 1940s to 1980. In the late 1940s, the policy and the institutions that implemented it were given objectives and forms similar to those in the USSR. This Soviet-type policy was in principle a non-exit policy; issuing a passport was an exception that required a solid justification. However, after 1953, following the Soviet Thaw, Polish leaders gradually relaxed the restrictions on exit, which allowed for massive outflows, mainly to Germany and Israel, and for development of temporary mobility, mainly within the Soviet bloc. In the late 1950s, the Polish party restricted emigration but it did not return to the Stalin-era non-exit model. The party developed a new, complex passport policy, which favorably viewed mobility within the bloc and was selective toward travel to the West. This allowed international mobility to expand to a mass scale and become part of the lived experience of millions of Poles. The police apparatus that implemented the policy also expanded and evolved into a complex bureaucratic machinery, but to its end it combined the features of a Weberian bureaucracy with the characteristics of a revolutionary, extralegal “secular arm of the party.”

Loop Extended Symbolic Execution on List Manipulating Programs

Current symbolic execution is challenged by its ability to deal with loops. The case gets worse for loops manipulating recursive data structures. In this paper, we extend classic symbolic execution techniques for error detection of programs manipulating lists in loops. The idea is to enhance the symbolic execution with the utilization of quantitative aspect of the shape, and to construct the exit state of the loop. The exit state is constrained by a set of numeric constraints containing normal symbolic variables in programs and instrumented symbolic variables on the shapes. A prototype tool has been implemented and experiments are conducted on some commonly used list manipulating programs.