Complexity Theory, Game Theory, and Economics: The Barbados Lectures

This document collects the lecture notes from my mini-course "Complexity Theory, Game Theory, and Economics," taught at the Bellairs Research Institute of McGill University, Holetown, Barbados, February 19--23, 2017, as the 29th McGill Invitational Workshop on Computational Complexity. The goal of this mini-course is twofold: (i) to explain how complexity theory has helped illuminate several barriers in economics and game theory; and (ii) to illustrate how game-theoretic questions have led to new and interesting complexity theory, including recent several breakthroughs. It consists of two five-lecture sequences: the Solar Lectures, focusing on the communication and computational complexity of computing equilibria; and the Lunar Lectures, focusing on applications of complexity theory in game theory and economics. No background in game theory is assumed.Comment: Revised v2 from December 2019 corrects some errors in and adds some recent citations to v1 Revised v3 corrects a few typos in v

Essays In Industrial Organization And Applied Microeconomics

This dissertation consists of three essays in the areas of Industrial Organization and Applied Microeconomics. The first essay studies high-tech firms\u27 product portfolio choices under competition. I develop a model of dynamic portfolio adjustments in the context of the Chinese smartphone market, using the product life cycle as an empirically tractable heuristic to capture firms\u27 dynamic incentives in new product introductions. I first show that product life cycles endogenously arise in markets with rapid technological innovations, are heterogeneous across products, and are affected by the level of market competition. I then estimate smartphone demand and manufacturers\u27 variable, maintenance and sunk introduction costs on a detailed monthly market-level dataset of Chinese smartphones between 2009 and 2014. Finally, I use a 2012 large-scale pro-competitive policy introduced by the Chinese government as an experiment to decompose the handset manufacturers\u27 incentives to introduce new products and show that the increased competition reduces the average product\u27s short-run profits by 5% but its lifetime profits by 41% by shrinking its product life cycle. These dynamic incentives have large implications for both consumer welfare gains from product variety and the speed of technology adoption in this market. In the second essay, my co-authors and I explore the sensitivity of the U.S. government\u27s ongoing incentive auction to multi-license ownership by broadcasters. We document significant broadcast TV license purchases by private equity firms prior to the auction and perform a prospective analysis of the effect of ownership concentration on auction outcomes. We find that multi-license holders are able to raise spectrum acquisition costs by 22% by strategically withholding some of their licenses to increase the price for their remaining licenses. We analyze a potential rule change that reduces the distortion in payouts to license holders by up to 80%, but find that lower participation could greatly increase payouts and exacerbate strategic effects. The third essay studies whether liberalizations of gun permits in the U.S. deterred violent crimes. Setting off an ongoing controversy, Lott and Mustard (1997) famously contended that so-called shall-issue laws (SILs) deterred violent crime. In this controversy the weapon of choice has been the differences-in-differences (DD) estimator applied to state and county panel data spanning various intervals of time. By treating violent crime as a career choice, this essay brings to bear a more general method, a cohort panel data model (CPDM) that incorporates the fundamental dynamic insights regarding entering and exiting a career. Our model distinguishes among three key parameters that jointly determine the effect of SILs on crime, (i) a direct effect on entry decisions, (ii) a surprise effect on exit decisions by individuals who entered criminal careers prior to the passage of SILs, and (iii) a selection effect on exit decisions by those who entered in the presence of SILs. We find significant and time-invariant results that reject the deterrence hypothesis as well as the DD model specification. Our results suggest that passages of SILs contribute to about one third of total violent crimes in 2011, particularly through higher turnover of violent criminals

Performance model for two-tier mobile wireless networks with macrocells and small cells

[EN] A new analytical model is proposed to evaluate the performance of two-tier cellular networks composed of macrocells (MCs) and small cells (SCs), where terminals roam across the service area. Calls being serviced by MCs may retain their channel when entering a SC service area, if no free SC channels are available. Also, newly offered SC calls can overflow to the MC. However, in both situations channels may be repacked to vacate MC channels. The cardinality of the state space of the continuous-time Markov chain (CTMC) that models the system dynamics makes the exact system analysis unfeasible. We propose an approximation based on constructing an equivalent CTMC for which a product-form solution exist that can be obtained with very low computational complexity. We determine performance parameters such as the call blocking probabilities for the MC and SCs, the probability of forced termination, and the carried traffic. We validate the analytical model by simulation. Numerical results show that the proposed analytical model achieves very good precision in scenarios with diverse mobility rates and MCs and SCs loads, as well as when MCs overlay a large number of SCs.Authors would like to thank you the anonymous reviewers for the review comments provided to our work that have decisively contributed to improve the paper. Most of the contribution of V. Casares-Giner was done while visiting the Huazhong University of Science and Technolgy (HUST), Whuhan, China. This visit was supported by the European Commission, 7FP, S2EuNet project. The authors from the Universitat Politecnica de Valencia are partially supported by the Ministry of Economy and Competitiveness of Spain under grant TIN2013-47272-C2-1-R and TEC2015-71932-REDT. The research of Xiaohu Ge was supported by the National Natural Science Foundation of China (NSFC) grant 61210002, the Fundamental Research Funds for the Central Universities grant 2015XJGH011, and China International Joint Research Center of Green Communications and Networking grant 2015B01008.Casares-Giner, V.; Martínez Bauset, J.; Ge, X. (2018). Performance model for two-tier mobile wireless networks with macrocells and small cells. Wireless Networks. 24(4):1327-1342. https://doi.org/10.1007/s11276-016-1407-8S13271342244ABIresearch. (2016). In-building mobile data traffic forecast. ABIreseach, Technical Report.NGMN Alliance. (2015). Recommendations for small cell development and deployment. NGMN Alliance, Technical Report.Chandrasekhar, V., Andrews, J., & Gatherer, A. (2008). Femtocell networks: A survey. IEEE Communications Magazine, 46(9), 59–67.Yamamoto, T., & Konishi, S. (2013). Impact of small cell deployments on mobility performance in LTE-Advanced systems. In IEEE PIMRC workshops (pp. 189–193).Balakrishnan, R., & Akyildiz, I. (2016). Local anchor schemes for seamless and low-cost handover in coordinated small cells. IEEE Transactions on Mobile Computing, 15(5), 1182–1196.Zahir, T., Arshad, K., Nakata, A., & Moessner, K. (2013). Interference management in femtocells. IEEE Communications Surveys & Tutorials, 15(1), 293–311.Yassin, M., AboulHassan, M. A., Lahoud, S., Ibrahim, M., Mezher, D., Cousin, B., & Sourour, E. A. (2015). Survey of ICIC techniques in LTE networks under various mobile environment parameters. Wireless Networks, 1–16.Andrews, M., & Zhang, L. (2015). Utility optimization in heterogeneous networks via CSMA-based algorithms. Wireless Networks, 1–14.El-atty, S. M. A., & Gharsseldien, Z. M. (2016). Performance analysis of an advanced heterogeneous mobile network architecture with multiple small cell layers. Wireless Networks, 1–22.Huang, Q., Huang, Y.-C., Ko, K.-T., & Iversen, V. B. (2011). Loss performance modeling for hierarchical heterogeneous wireless networks with speed-sensitive call admission control. IEEE Transactions on Vehicular Technology, 60(5), 2209–2223.Bonald, T., & Roberts, J. W. (2003). Congestion at flow level and the impact of user behaviour. Computer Networks, 42, 521–536.Lee, Y. L., Chuah, T. C., Loo, J., & Vinel, A. (2014). Recent advances in radio resource management for heterogeneous LTE/LTE-A networks. IEEE Communications Surveys & Tutorials, 16(4), 2142–2180.Rappaport, S. S., & Hu, L.-R. (1994). Microcellular communication systems with hierarchical macrocell overlays: Traffic performance models and analysis. Proceedings of the IEEE, 82(9), 1383–1397.Ge, X., Han, T., Zhang, Y., Mao, G., Wang, C.-X., Zhang, J., et al. (2014). Spectrum and energy efficiency evaluation of two-tier femtocell networks with partially open channels. IEEE Transactions on Vehicular Technology, 63(3), 1306–1319.Song, W., Jiang, H., & Zhuang, W. (2007). Performance analysis of the WLAN-first scheme in cellular/WLAN interworking. IEEE Transactions on Wireless Communications, 6(5), 1932–1952.Ge, X., Martinez-Bauset, J., Gasares-Giner, V., Yang, B., Ye, J., & Chen, M. (2013). Modeling and performance analysis of different access schemes in two-tier wireless networks. In IEEE Globecom (pp. 4402–4407).Tsai, H.-M., Pang, A.-C., Lin, Y.-C., & Lin, Y.-B. (2005). Repacking on demand for hierarchical cellular networks. Wireless Networks, 11(6), 719–728.Maheshwari, K., & Kumar, A. (2000). Performance analysis of microcellization for supporting two mobility classes in cellular wireless networks. IEEE Transactions on Vehicular Technology, 49(2), 321–333.Whiting, P., & McMillan, D. (1990). Modeling for repacking in cellular radio. In 7th UK Teletraffic Symposium, IEE, Durham.Kelly, F. (1989). Fixed point models of loss networks. The Journal of the Australian Mathematical Society. Series B. Applied Mathematics, 31(02), 204–218.McMillan, D. (1991). Traffic modelling and analysis for cellular mobile networks. In A. Jensen & V. Iversen (Eds.), Proceedigs of ITC-13 (pp. 627–632). IAC. Copenhaguen: Elsevier Science.Fu, H.-L., Lin, P., & Lin, Y.-B. (2012). Reducing signaling overhead for femtocell/macrocell networks. IEEE Transactions on Mobile Computing, 12(8), 1587–1597.Eklundh, B. (1986). Channel utilization and blocking probability in a cellular mobile telephone system with directed retry. IEEE Transactions on Communications, 37, 329–337.Karlsson, J., & Eklundh, B. (1989). A cellular telephone system with load sharing—An enhancement of directed retry. IEEE Transactions on Communications, 37(5), 530–535.Nelson, R. (1995). Probability, stochastic processes and queueing theory. New York: Springer.Iversen, V.B. (Aug. 1987). The exact evaluation of multi-service loss systems with access control. In Proceedings of the Seventh Nordic Teletraffic Seminar (NTS-7) (Vol. 31, pp. 56–61) Lund, (Sweden).Ross, K. W. (1995). Multiservice loss models for broadband telecommunication networks. New York: Springer.Lin, Y.-B., & Mak, V. W. (1994). Eliminating the boundary effect of a large-scale personal communication service network simulation. ACM Transactions on Modeling and Computer Simulation (TOMACS), 4(2), 165–190.Karray, M.K. (2010). Evaluation of the blocking probability and the throughput in the uplink of wireless cellular networks. In IEEE ComNet (pp. 1–8)

Unit propagation with stable watches

Unit propagation is the hottest path in CDCL SAT solvers, therefore the related data-structures, algorithms and implementation details are well studied and highly optimized. State-of-the-art implementations are based on reduced occurrence tracking with two watched literals per clause and one blocking literal per watcher in order to further reduce the number of clause accesses. In this paper, we show that using runtime statistics for watched literal selection can improve the performance of state-of-the-art SAT solvers. We present a method for efficiently keeping track of spans during which literals are satisfied and using this statistic to improve watcher selection. An implementation of our method in the SAT solver CaDiCaL can solve more instances of the SAT Competition 2019 and 2020 benchmark sets and is specifically strong on satisfiable cryptographic instances

Proceedings of SAT Competition 2020 : Solver and Benchmark Descriptions

Non peer reviewe