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on Computational Economics |
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Issue of 2007‒09‒02
eight papers chosen by |
| By: | Rubin, Raphael |
| Abstract: | The DARPA Grand Challenge in which the Cornell Racing Team participates requires the completion of a Simulator, which purports all errors in the artificial intelligence path planning down below and back up. The simulator comes as the last layer in the top down approach followed by the Cornell Racing Team. The Strategic layer is charged of global route planning, the tactical layer of collision avoidance and maneuver planning, while the operational layer controls lane tracking and safe following. The simulator is the last layer. Through a COBRA interface the C++ or C# version of the simulator will be receiving commands from the Artificial Intelligence Strategic Layer concerning maneuvers such as Turn Left, Turn Right, Change Lane, Increase Speed, and Stop. The simulator induces from its current situation, using controls such as bounding boxes and the World class, pointing to every object in the World, a set of more detailed commands. Apart from writing a simplified version of the simulator in C++, we also concentrated my efforts onto finding a solution aside from dynamic programming for Path Planning and the Behavioral Modeling of Visible and Neighboring Vehicles on the road network. We have built an efficient and self-correcting C++ GUI Interface including some random moving vehicles as well as a smart vehicle named Autosmart. The Path Planning algorithm is written and implemented although may be missing a more significant round of testing. To do so, we are using the approach of game theory and artificial intelligence’s neural networks. We represent the world as nature, resulting in decisions independent of the drivers (types: turn left or right at the next intersection); nature being in this case the DARPA Challenge organizers. Moreover the drivers chose their behaviors (aggressive, altruist) on the road and keep updating their anticipations about the other players behavior and types, as mentioned above. The end result is to train these neural networks to react to previously categorized behaviors and situations by storing necessary information about the ‘game’. Every player runs its own network, although in our case we limited the simulation to one smart vehicle, Autosmart and 2 random vehicles; therefore by nature the algorithm the algorithm would lead to biased results. It is meant for simplicity since if not for programming the set of commands which lead to adequate behavior at intersections and on segments, such as being done for the smart vehicle; sometimes the random vehicles get into trouble, being too much off the road network. In most cases, the simulator will self-correct their path however. |
| Keywords: | C++; DARPA Urban Challenge; Game Theory; Artificial Intelligence; |
| JEL: | C70 |
| Date: | 2007–08–25 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:4603&r=cmp |
| By: | Kleijnen, J.P.C. (Tilburg University, Center for Economic Research) |
| Abstract: | In practice, simulation analysts often change only one factor at a time, and use graphical analysis of the resulting Input/Output (I/O) data. The goal of this article is to change these traditional, naive methods of design and analysis, because statistical theory proves that more information is obtained when applying Design Of Experiments (DOE) and linear regression analysis. Unfortunately, classic DOE and regression analysis assume a single simulation response that is normally and independently distributed with a constant variance; moreover, the regression (meta)model of the simulation model?s I/O behaviour is assumed to have residuals with zero means. This article addresses the following practical questions: (i) How realistic are these assumptions, in practice? (ii) How can these assumptions be tested? (iii) If assumptions are violated, can the simulation's I/O data be transformed such that the assumptions do hold? (iv) If not, which alternative statistical methods can then be applied? |
| Keywords: | metamodel;experimental design;jackknife;bootstrap;common random numbers;validation |
| JEL: | C0 C1 C9 |
| Date: | 2007 |
| URL: | http://d.repec.org/n?u=RePEc:dgr:kubcen:200730&r=cmp |
| By: | Bettonvil, B.W.M.; Castillo, E. del; Kleijnen, J.P.C. (Tilburg University, Center for Economic Research) |
| Abstract: | This paper studies simulation-based optimization with multiple outputs. It assumes that the simulation model has one random objective function and must satisfy given constraints on the other random outputs. It presents a statistical procedure for test- ing whether a specific input combination (proposed by some optimization heuristic) satisfies the Karush-Kuhn-Tucker (KKT) first-order optimality conditions. The pa- per focuses on "expensive" simulations, which have small sample sizes. The paper applies the classic t test to check whether the specific input combination is feasi- ble, and whether any constraints are binding; it applies bootstrapping (resampling) to test the estimated gradients in the KKT conditions. The new methodology is applied to three examples, which gives encouraging empirical results. |
| Keywords: | Stopping rule; metaheuristics; response surface methodology; design of experiments |
| JEL: | C0 C1 C9 C15 C44 C61 |
| Date: | 2007 |
| URL: | http://d.repec.org/n?u=RePEc:dgr:kubcen:200745&r=cmp |
| By: | ABE Kazutomo |
| Abstract: | This paper presents assessments of the economic impacts of free trade agreements (FTAs) relating to Japan. The analysis relies on a simulation with a computable equilibrium model. The impacts of various combinations of FTAs are assessed to draw policy implications. This paper first reviews the theoretical framework, together with the specifications of the simulation model. Then, simulations in the various cases cover both Japan's bilateral FTAs and regional FTAs including Japan. The final section is a short summary of implications from the simulation work. |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:eti:dpaper:07053&r=cmp |
| By: | Chong Soo Yuen (Singapore Centre for Applied and Policy Economics, Department of Economics, National University of Singapore); Jung Hur (Department of Economics, National University of Singapore) |
| Abstract: | The proliferation of overlapping free trade agreements (FTA) in the recent years has led to hub-and-spokes (HAS) throughout the world. Being avid subscribers to FTAs, many countries in the Asia-Pacific region including the USA, Japan, Singapore, South Korea, Thailand and Australia have become trade hubs to their partners who are in turn relegated to spoke status. In this paper, we question whether being a hub is welfare optimal for a small and open economy like Singapore compared to membership in a single bilateral FTA or a multi- member free trade zone. Within this context, we use a computable general equilibrium model to examine the welfare implications of the triangular trade relationship of the USA, Singapore and Japan. This is facilitated by the Japan- Singapore Economic Partnership Agreement, the USA-Singapore Free Trade Agreement, and a hypothetical USA-Japan Economic Partnership Agreement. The analysis is extended to incorporate “super-hub” effects; that is, the spoke countries can be trade hubs in other HAS systems. The experiment reveals that hub status generates positive welfare gain and is the highest Singapore can get from the trade configurations considered. Meanwhile, Japan loses more than the USA when both are relegated to spoke status. These findings prove robust under different market structures and production technologies, deeper economic integration, “super-hub” effects, as well as, uncertainty in the key model parameters and the extent of trade liberalisation shocks. |
| Keywords: | hub and spokes; overlapping agreements; free trade; preference dilution; computable general equilibrium; GTAP; systems; trade configurations |
| JEL: | C68 D58 F15 |
| URL: | http://d.repec.org/n?u=RePEc:sca:scaewp:0711&r=cmp |
| By: | Christian Upper |
| Abstract: | Researchers at central banks increasingly turn to counterfactual simulations to estimate the danger of contagion owing to exposures in the interbank loan market. The present paper summarises the findings of such simulations, provides a critical assessment of the modelling assumptions on which they are based, and discusses their use in financial stability analysis. On the whole, such simulations suggest that contagious defaults are unlikely, but cannot be fully ruled out, at least in some countries. If contagion does take place, then it could lead to the breakdown of a substantial fraction of the banking system, thus imposing high costs to society. However, when interpreting these results, one has to bear in mind the potential bias caused by the very strong assumptions underlying the simulations. While robustness tests indicate that the models might be able to correctly predict whether or not contagion could be an issue and, possibly, also identify critical institutions, they are less suited for stress testing or for the analysis of policy options in crises, primarily due to their lack of behavioural foundations. Going forward, more work is needed on how to attach probabilities to the individual scenarios and on the microfoundations of the models. |
| Keywords: | Contagion, interbank lending, domino effects, systemic risk |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:bis:biswps:234&r=cmp |
| By: | Olivier Bargain (University College Dublin, CHILD and IZA); Leszek Morawski (University of Warsaw); Michal Myck (DIW Berlin, IFS and IZA); Mieczyslaw Socha (University of Warsaw) |
| Abstract: | The Polish tax and benefit system is presented in the context of a recently developed microsimulation model, SIMPL. The model allows simulating direct taxes, social contributions and public benefits in Poland for the years 2003 and 2005. It is based on the Household Budgets Survey data (Badania Budzetów Gospodarstw Domowych) from 2003 and 2005. The document describes details of the Polish tax and benefit system and the simulation assumptions which were necessary in modelling it in SIMPL. We provide information on the quality of the data used in the model and some details of the validation process through various robustness checks. Finally we provide examples of application of the model for analysis of effects of policy reforms. |
| Keywords: | microsimulation, tax and benefit systems, income distribution, Poland |
| JEL: | H24 H31 I32 I38 |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp2988&r=cmp |
| By: | Christian Offermanns (Frankfurt University and Deutsche Bundesbank); Marcus Pramor (Center for Financial Studies) |
| Abstract: | This paper documents the methodology underlying the construction of a global database of gross foreign asset and liability positions for 153 countries over the period 1970 to 2004 and illustrates some key data characteristics. The data cover both inflows and outflows of capital and thus allow for an assessment of the degree of international financial integration. In addition to net foreign asset stocks, we also provide details on the composition of the main asset and liability categories, namely the foreign direct investment, equity investment and debt components. Finally, we report on valuation changes as one of the main sources of discrepancy between transaction-based capital flow data and stock values of investment positions. The dataset is available for download at www.ifk-cfs.de/fileadmin/downloads/data/ cfs-icfd.zip. |
| Keywords: | Net Foreign Assets; Valuation Adjustment; International Financial Integration |
| JEL: | F21 F34 F32 |
| Date: | 2007–08–24 |
| URL: | http://d.repec.org/n?u=RePEc:cfs:cfswop:wp200724&r=cmp |