Abstract:We show that an essential step in the PARTAN variant of the Frank–Wolfe algorithm for equilibrium assignment, the calculation of a minimal step length for maintaining feasibility, can be accomplished using either analytical formulas or simple rules.
“…In the early papers these bounds were determined individually for the first few steps. Later, (Arezki & van Vliet, 1990) and (Florian, Guelat, & Spiess, 1987) determined analytical recursion formulas for these bounds. In spite of improved convergence characteristics, the PARTAN approach has not superseded the Frank-Wolfe method in the telecom and transportation areas.…”
We present versions of the Frank-Wolfe method for linearly constrained convex programs, in which consecutive search directions are made conjugate. Preliminary computational studies in a MATLAB environment applying pure Frank-Wolfe, Conjugate direction Frank-Wolfe (CFW), Bi-conjugate Frank-Wolfe (BFW) and "PARTANized" Frank-Wolfe methods to some classical Traffic Assignment Problems show that CFW and BFW compare favorably to the other methods. This spurred a more detailed study, comparing our methods to Bar-Gera's origin-based algorithm. This study indicates that our methods are competitive for accuracy requirements suggested by Boyce et al. We further show that CFW is globally convergent. We further point at independent studies by other researchers that show that our methods compare favourably with recent bush-based and gradient projection algorithms on computers with several cores.
“…In the early papers these bounds were determined individually for the first few steps. Later, (Arezki & van Vliet, 1990) and (Florian, Guelat, & Spiess, 1987) determined analytical recursion formulas for these bounds. In spite of improved convergence characteristics, the PARTAN approach has not superseded the Frank-Wolfe method in the telecom and transportation areas.…”
We present versions of the Frank-Wolfe method for linearly constrained convex programs, in which consecutive search directions are made conjugate. Preliminary computational studies in a MATLAB environment applying pure Frank-Wolfe, Conjugate direction Frank-Wolfe (CFW), Bi-conjugate Frank-Wolfe (BFW) and "PARTANized" Frank-Wolfe methods to some classical Traffic Assignment Problems show that CFW and BFW compare favorably to the other methods. This spurred a more detailed study, comparing our methods to Bar-Gera's origin-based algorithm. This study indicates that our methods are competitive for accuracy requirements suggested by Boyce et al. We further show that CFW is globally convergent. We further point at independent studies by other researchers that show that our methods compare favourably with recent bush-based and gradient projection algorithms on computers with several cores.
“…Chabini et al [14] also contains parallel computing implementations of a shortest paths algorithm due to Dijkstra [22]. The linear approximation method used to solve the fixed demand network equilibrium problem by Chabini et al [14], is an adaptation of the Frank-Wolfe algorithm [27,4]. In the sequential implementation of this algorithm a variant of Dijkstra's [22] algorithm is used to calculate shortest routes for all origin-destination pairs.…”
“…As it is well-known that the standard Frank-Wolfe algorithm sometimes shows poor convergence (see, e.g., Sheffi 1985;Patriksson 1994;Florian and Hearn 1995), we consider an improved version called Partan that was proposed by LeBlanc, Helgason, and Boyce (1985) and further studied by Florian, Guélat, and Spiess (1987) and Arezki and Van Vliet (1990), among others. As we cannot explicitly work with all variables x P associated with paths P ∈ P ϕ , because there may be exponentially many, we only generate them when needed.…”
Abstract. The design of route guidance systems faces a well-known dilemma. The approach that theoretically yields the system-optimal traffic pattern may discriminate against some users in favor of others. Proposed alternate models, however, do not directly address the system perspective and may result in inferior performance. We propose a novel model and corresponding algorithms to resolve this dilemma. We present computational results on real-world instances and compare the new approach with the well-established traffic assignment model. The essence of this study is that system-optimal routing of traffic flow with explicit integration of user constraints leads to a better performance than the user equilibrium, while simultaneously guaranteeing superior fairness compared to the pure system optimum.
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