PhD theses that contributed to GeoDiverCity programme


phd-swerts

Swerts E., 2013, The Indian and Chinese Systems of Cities , University Paris I.

Abstract. This thesis compares the urban systems in China and India using dedicated data bases that have been constructed using comparable and harmonized principles, describing the evolution of the population of all urban agglomerations above 10 000 inhabitants, every ten years from the beginning of 20th century for India and 1964 for China. Both very large countries of ancient urbanization are characterized by many small towns and have developed gigantic metropolises during the last decades. Despite their geo-historical specific features, these two systems share with others in the world the same properties of hierarchical differentiation and urban growth processes (Zipf’s law and Gibrat’s model), at country scale as well as for regional subsystems. A regional diversity is linked to former processes of unequal concentration of urban development. The most interesting result is identifying for the first time a reverse trend in the evolution of the Chinese urban hierarchy compared to other countries in the world among which India: despite the very rapid recent urban growth, the inequalities in city sizes are decreasing. This may in part depend of the under-registration of migrant urban populations. It also reveals the power of the political control on China’s urban processes that also appears in the magnitude of spatial concentration of manufacturing cities due to the implantation of Special economic Zones. Comparing the trajectories of Indian and Chinese cities may well improve the prospect of global urbanization that is crucial for the world and the planet.

Key-words. System of cities, Urban hierarchy, Zipf, Gibrat, Urban trajectories, China, India.

Link. HAL-SHS.



PhD Clémentine Cottineau

Cottineau C., 2014, The evolution of cities in the post-Soviet Space. Observation and modellings, University Paris I.

Abstract. The Russian and Soviet urbanisation process happened late and fast, compared to other territories. Many new towns and cities were created by the Soviet regime that officially promoted discourses about the socialist function of the city, rational organisation of space and a planned management of the economy. These urban particularities and the multiple demographic and political events of the 20th century have made cities in the post-Soviet space an interesting case and raised question regarding its ruptures and comparability. This dissertation thesis aims to show that the concept of system of cities and generic methods in urban geography (especially models) are useful in the study of urban evolution over the long term in this space, to eventually better understand past trends and predict future ones. We confronted several statistical models with the observed urban dynamics and concluded that the macro-geographical structure of cities in the post-Soviet space was comparable to that of other systems of cities (hierarchy of sizes, spacing, functional differentiation). We also observed specific trajectories related to the size of the territory, natural resources, the recent demographic shrinkage and the effect of particular political decisions. This knowledge about observed evolutions has been included in an incremental approach of agent-based modeling. Starting from theoretical hypotheses about generative mechanisms, we tried to generate generic and specific stylised facts, with a model as parsimonious as possible. The progressive evaluation of increasingly complex models led to the satisfactory simulation of observed urban evolution and highlighted specific trajectories that “resist” modeling.

Key-words. System of cities, Post-Soviet Space, Soviet Union, Generic/Specific, Simulation, Urban evolution, Urban growth.

Link. HAL-SHS.



PhD Clara Schmitt

Schmitt C., 2014, Modeling settlements systems dynamics : from SimpopLocal to SimpopNet, University Paris I.

Abstract. Is urban growth the result of multiple interactions between cities ? Urban evolutionary theory (Pumain, 2000), based on this postulate, analyses urban growth processes. This thesis, undertaken in an inter-disciplinary context, aims to evaluate the validity of the hypothesis by means of computer simulation. Strong regularities of the urban systems dynamics are extracted from the accumulated scientific knowledge and synthetized into ten major stylized facts. Two simulation models, SimpopLocal and SimpopNet, are then built, documented – thanks to a standardized grid – and systematically explored. They each question a specific aspect of the urban evolutionary theory : the nature of the inter-urban interactions for the first model (i.e. competition for innovation) and their support for the second model (i.e. the role of the communication network structure). The evaluation of the two models required the design and the implementation of two original exploration protocols : an automated calibration method and a sensibility analysis protocol (the Exploration Profile algorithm) which individually evaluates the contribution of each implemented mechanism to the simulated behavior. These two forms of exploration systematically confront the simulation results with current scientific knowledge. They indicate that the two models are able to account for key processes of urban systems dynamics, such as their hierarchical organization, and demonstrate for the first time the need for interurban interaction mechanisms in order to simulate urban evolutions that are close to those observed on real urban systems.

Key-words. System of cities, Urban systems, Simpop, SimpopLocal, SimpopNet, Simulation, Urban evolution, Urban growth.

Link. HAL-SHS.


Phd Ignazzi

Ignazzi C. A., 2015, Coevolution in the Brazilian Urban System, University Paris I.

Abstract. This thesis analyzes the urban system in Brazil adopting an advanced database that have been constructed collecting demographic data in order to examine the evolution of the population of all Brazilian agglomerations since the first Brazilian official census carried out in 1872 until 2010.
The largest country of South America has already completed its urban transition during the last century and is characterized by the contrast between a larger number of small towns throughout the immense territory and enormous Metropolitan areas dominating the system of cities.
Despite its geographical and historical peculiarities, this system shares with others in the world the same properties of hierarchical differentiation and urban growth processes (Zipf’s law and Gibrat’s model).
Economic data have been integrated in the database with the aim of testing the validity of scaling laws for Brazil and performing robust statistical analysis in order to explore the functional differentiation of cities, their economic performances and the spatial autocorrelation processes occurring among them.
The most interesting result is characterizing the Brazilian urban hierarchy over the long period and measuring the increasing inequalities in city sizes. Moreover, the parallel support of demographic and economic data is essential to identify the connection between population and economic growth in one of the most urbanized country of the world.

Key-words. System of cities, Urban systems, Urban hierarchy, Zipf, Gibrat, Urban trajectories, Brazil, Functional differentiation, spatial autocorrelation.

Link. Online.



PhD Rey-Coyrehourcq

Rey-Coyrehourcq S., 2015, An integrated platform for building and evaluating model of simulation in geography, University Paris I.

Abstract. Since 1990’s, Agent Based Modelling are commonly used by geographers to study complex systems like cities.
However, very few technical platforms are advanced by searchers to assist in the construction and evaluation of models of simulation. With the help of ERC program GeoDiverCity and the formation of an expert interdisciplinary team, we try to solve these problematic following two objectives. Relying on the support of OpenMOLE platform developed at the Institute of Complex System Paris-Ile-de-France in order to make it simple the distribution of simulation on distributed computing environments, we identify, use or build new tools and methodology to construct and explore model of simulation. To anchor this work in practice, we use this platform to build and explore a new model of simulation: SimpopLocal. This very practical work is accompanied by an historical and epistemological reading of simulation, and the means of simulation in geography. These contextualisation permits us to examine, and perhaps to anticipate, the historical link between the old problematic of “Validation”, very important to consider for knowledge justification, and the building and exploration of models of simulation.

Key-words. Simulation, Agent Based Modelling, Complex systems, Distributed computing environments, Validation.

Link. Online.



PhD Solène Baffi

Baffi S., 2015, Railways and city in territorialization processes in South Africa : from separation to integration?, University Paris I.

Abstract. First railway network in Africa, the South African Railways constitute a privileged marker of the territorial mutations that have been shaping this country for decades. The radicalism of political systems shows through the persistency of segregative schemes of which the railways, as part of the planning toolbox, are one of the elements. The inertia of this infrastructure questions its re-appropriation and insertion into the various planning projects over the long term. This thesis approaches the long-term dynamics of ‘territorialisation’ in South Africa through the prism of railways. This study focuses on the interaction between cities and the railway network, at both the interurban and the intra-urban levels.
In order to understand this interaction, cities’ location and railways diffusion patterns are analysed, with a specific emphasis on the shape of the network. Indeed, through their pattern, railways express the intentions of actors in charge of planning at the national level. By the flows it supports and the mobilities it enhances, it gives us information on the socioeconomic requirements of society and the power relations it contains. Thus, this thesis relies on a qualitative and quantitative approach aiming to outline the structuring effects of the railways in South Africa over the long term.
Its political use by successive segregationist powers explains partly why nowadays railways keep on marking partition in the post-apartheid urban space and in the practices of city dwellers. However, the recent rail renewal observed in the metropolises, Cape Town in particular, might indicate a possible major inflection in the persistency of inherited dynamics. Indeed, the evolution of the rail offer demonstrates a shift towards a co-construction trend between South African society and urban planning unheard of until now.

Key-words. System of cities, Urban system, South Africa, Railways, Territorialisation, Inclusion/exclusion, Intra-urban mobilities.

Link. HAL-SHS.



PhD Olivier Finance

Finance O., 2016, French cities hosting foreign direct investments: from networked companies to localized establishments, University Paris I.

Abstract. Transnational corporations, which are amongst the major players in the contemporary global economy, integrate and exclude territories at various scales, due to their specific location strategies. These inequalities are well known at an international scale, yet the knowledge of this diverse integration is much more limited regarding urban levels, although cities and metropolises are considered as being the major nodes of the globalized networks. France and the OECD countries certainly appear in central positions in the networks that characterize these corporations, but observations made at the urban level remain very partial due to the lack of localized data. This thesis suggests to both approach and localize conventional data about Foreign Direct Investment (FDI) in the French case by mobilizing data about financial links connecting economic units. The detailed breakdown of transnational corporations affiliation networks has been conducted up to the level of the establishments, which are the real individual economic and geographic cells of these transnational networks. An original database about localized inward FDI stocks has been built and explored to appreciate how far foreign transnational corporations integrate the 355 main cities into the French urban system. These data revealed the diverse integration of French cities, between dependence and attractiveness for the investors. The mobilization of scaling laws, which constituted a major analytical tool in this work, allowed us to identify the major factors explaining the diverse integration of French cities into the whole system of cities, reflected both by inequalities of hierarchical and regional order.

Key-words. System of cities, Urban system, France, Scaling laws, Foreign Direct Investment, Transnational firms.

Link. HAL-SHS.


Urban Dynamics and Simulation Models

Urban Dynamics and Simulation Models | ERC GeoDiverCityNew book, published by Springer International.


Pumain D., Reuillon R. (eds.), 2017, Urban Dynamics and Simulation Models, Springer, 123p.
DOI 10.1007/978-3-319-46497-8

Authors. Chapron P., Chérel G., Cottineau C., Cura R., Leclaire M., Pumain D., Rey-Coyrehourcq S., Reuillon R., Schmitt C., Swerts E.

Abstract. This monograph presents urban simulation methods that help in better understanding urban dynamics. Over historical times, cities have progressively absorbed a larger part of human population and will concentrate three quarters of humankind before the end of the century. This “urban transition” that has totally transformed the way we inhabit the planet is globally understood in its socio-economic rationales but is less frequently questioned as a spatio-temporal process. However, the cities, because they are intrinsically linked in a game of competition for resources and development, self organize in “systems of cities” where their future becomes more and more interdependent. The high frequency and intensity of interactions between cities explain that urban systems all over the world exhibit large similarities in their hierarchical and functional structure and rather regular dynamics. They are complex systems whose emergence, structure and further evolution are widely governed by the multiple kinds of interaction that link the various actors and institutions investing in cities their efforts, capital, knowledge and intelligence. Simulation models that reconstruct this dynamics may help in better understanding it and exploring future plausible evolutions of urban systems. This would provide better insight about how societies can manage the ecological transition at local, regional and global scales. The author has developed a series of instruments that greatly improve the techniques of validation for such models of social sciences that can be submitted to many applications in a variety of geographical situations. Examples are given for several BRICS countries, Europe and United States. The target audience primarily comprises research experts in the field of urban dynamics, but the book may also be beneficial for graduate students.

Key-words. Simulation, Simulation models, Simpop, Systems of Cities, Complexity, Urban systems, Urban systems dynamics, BRICS.

Link. http://www.springer.com/us/book/9783319464954

A modular modelling framework for hypotheses testing in the simulation of urbanisation

New Article, in Systems.


Cottineau C., Reuillon R., Chapron P., Rey-Coyrehourcq R., Pumain D., 2015, « A Modular Modelling Framework for Hypotheses Testing in the Simulation of Urbanisation », Systems, 3, Special Issue Agent-Based Modelling of City Systems, pp. 348-377, DOI:10.3390/systems3040348

Abstract. In this paper, we present a modelling experiment developed to study systems of cities and processes of urbanisation in large territories over long time spans. Building on geographical theories of urban evolution, we rely on agent-based models to 1) formalise complementary and alternative hypotheses of urbanisation and 2) explore their ability to simulate observed patterns in a virtual laboratory. The paper is therefore divided into two sections : an overview of the mechanisms implemented to represent competing hypotheses used to simulate urban evolution; and an evaluation of the resulting model structures in their ability to simulate—efficiently and parsimoniously—a system of cities (between 1000 and 2000 cities in the Former Soviet Union) over several periods of time (before and after the crash of the USSR). We do so using a modular framework of model-building and evolutionary algorithms for the calibration of several model structures. This project aims at tackling equifinality in systems dynamics by confronting different mechanisms with similar evaluation criteria. It enables the identification of the best-performing models with respect to the chosen criteria by scanning automatically the parameter space along with the space of model structures (the different combinations of mechanisms).

Key-words. system of cities; ABM; simulation; former soviet union; equifinality; multimodelling

Growing Models from the Bottom Up. An Evaluation-Based Incremental Modelling Method (EBIMM) Applied to the Simulation of Systems of Cities

MARIUS_Fig1New Paper, in JASSS


Cottineau C., Chapron P., Reuillon R., 2015, « Growing Models from the Bottom Up. An Evaluation-Based Incremental Modelling Method (EBIMM) Applied to the Simulation of Systems of Cities », Journal of Artificial Societies and Social Simulation 18 (4) 9. doi:10.18564/jasss.2828

Abstract. This paper presents an incremental method of parsimonious modelling using intensive and quantitative evaluation. It is applied to a research question in urban geography, namely how well a simple and generic model of a system of cities can reproduce the evolution of Soviet urbanisation. We compared the ability of two models with different levels of complexity to satisfy goals at two levels. The macro-goal is to simulate the evolution of the system’s hierarchical structure. The micro-goal is to simulate its micro-dynamics in a realistic way. The evaluation of the models is based on empirical data through a calibration that includes sensitivity analysis using genetic algorithms and distributed computing. We show that a simple model of spatial interactions cannot fully reproduce the observed evolution of Soviet urbanisation from 1959 to 1989. A better fit was achieved when the model’s structure was complexified with two mechanisms. Our evaluation goals were assessed through intensive sensitivity analysis. The complexified model allowed us to simulate the evolution of the Soviet urban hierarchy.

Key-words. ABM, Model-Building, System of Cities, Former Soviet Union, Evaluation, Incremental


Beyond Corroboration: Strengthening Model Validation by Looking for Unexpected Patterns

diversityNew Paper, in PLoS ONE


Chérel G., Cottineau C., Reuillon R., 2015, « Beyond Corroboration: Strengthening Model Validation by Looking for Unexpected Patterns », PLoS ONE 10(9): e0138212. doi:10.1371/journal.pone.0138212

Abstract. Models of emergent phenomena are designed to provide an explanation to global-scale phenomena from local-scale processes. Model validation is commonly done by verifying that the model is able to reproduce the patterns to be explained. We argue that robust validation must not only be based on corroboration, but also on attempting to falsify the model, i.e. making sure that the model behaves soundly for any reasonable input and parameter values. We propose an open-ended evolutionary method based on Novelty Search to look for the diverse patterns a model can produce. The Pattern Space Exploration method was tested on a model of collective motion and compared to three common a priori sampling experiment designs. The method successfully discovered all known qualitatively different kinds of collective motion, and performed much better than the a priori sampling methods. The method was then applied to a case study of city system dynamics to explore the model’s predicted values of city hierarchisation and population growth. This case study showed that the method can provide insights on potential predictive scenarios as well as falsifiers of the model when the simulated dynamics are highly unrealistic.

Key-words. Simulation and Modelling, Evolutionary Algorithm, Population Growth, Space Exploration, Urbanisation, Complex Systems.

A New Method to Evaluate Simulation Models: The Calibration Profile (CP) Algorithm

New publication, in JASSS : Journal of Artificial Societies and Social Simulation


Reuillon R., Schmitt C., De Aldama R., Mouret J.-B., 2015, « A New Method to Evaluate Simulation Models: The Calibration Profile (CP) Algorithm », JASSS : Journal of Artificial Societies and Social Simulation, Vol. 18, Issue 1, http://jasss.soc.surrey.ac.uk/18/1/12.html

Abstract. Models of social systems generally contain free parameters that cannot be evaluated directly from data. A calibration phase is therefore necessary to assess the capacity of the model to produce the expected dynamics. However, despite the high computational cost of this calibration it doesn’t produce a global picture of the relationship between the parameter space and the behaviour space of the model. The Calibration Profile (CP) algorithm is an innovative method extending the concept of automated calibration processes. It computes a profile that depicts the effect of each single parameter on the model behaviour, independently from the others. A 2-dimensional graph is thus produced exposing the impact of the parameter under study on the capacity of the model to produce expected dynamics. The first part of this paper is devoted to the formal description of the CP algorithm. In the second part,we apply it to an agent based geographical model (SimpopLocal). The analysis of the results brings to light novel insights on the model.

Key-words. Calibration Profile, Model Evaluation

Half a billion simulations: Evolutionary algorithms and distributed computing for calibrating the SimpopLocal geographical model

New publication, in Environment and Planning B.


Schmitt C, Rey-Coyrehourcq S, Reuillon R, Pumain D, 2015, “Half a billion simulations: evolutionary algorithms and distributed computing for calibrating the SimpopLocal geographical model” Environment and Planning B: Planning and Design, 42(2), 300-315. http://www.envplan.com/abstract.cgi?id=b130064p

Abstract. Multiagent geographical models integrate very large numbers of spatial interactions. In order to validate these models a large amount of computing is necessary for their simulation and calibration. Here a new data-processing chain, including an automated calibration procedure, is tested on a computational grid using evolutionary algorithms. This is applied for the first time to a geographical model designed to simulate the evolution of an early urban settlement system. The method enables us to reduce the computing time and provides robust results. Using this method, we identify several parameter settings that minimize three objective functions that quantify how closely the model results match a reference pattern. As the values of each parameter in different settings are very close, this estimation considerably reduces the initial possible domain of variation of the parameters. Thus the model is a useful tool for further multiple applications in empirical historical situations.

Keywords: simulation model, multiagent system, calibration, evolutionary algorithm, geographical modelling, high-performance computing, model validation

Multi-agent modeling of urban growth distribution in systems of cities

A strong regularity in urban systems has long been identified : the hierarchical distribution of city sizes. Moreover, a closer observation of the evolution of this distribution shows that in the majority of city systems, there is a trend towards a more and more unequal distribution of city sizes. Why does the majority of urban systems show those strong regularities? What are the common growth processes involved? Several dynamic growth models have been proposed but no consensus has yet been reached because of the under-determination of models by those empirical laws. In this presentation we describe a new method of agent-based parsimonious modeling that we think can contribute to the identification of the common urban growth processes. This modeling method is based  on  intensive model exploration for quantitative evaluation of implemented mechanisms. The exploration tools were first developed for the evaluation of SimpopLocal, a model of the organization of urban systems when cities first emerged. The use of those exploration tools was then generalized into a modeling method that was applied for the first time with the construction of the MARIUS family of models which aims at reproducing the evolution of Soviet urbanisation between 1959 and 1989. Those two examples show how this new modeling method can help the construction of urban theories by helping the evaluation of assumptions made on urban processes.

Download (PDF, 3.51MB)

Communication at the seminar Quanturb, ISC-PIF (Paris), November 19th.

Clara Schmitt and Paul Chapron

OpenMOLE 1.0

 It’s finally there!

After 6 years of hard work we made it to 1.0 (Heroic Hippo). It combines stability and ergonomic interfaces to provide the best model exploration tool ever made. OpenMOLE is a workflow engine designed to leverage the computing power of distributed execution environments for naturally parallel processes. A process is said naturally parallel if the same computation runs many times for a set of different inputs, such as model experiment or data processing…

We are very proud of this success, that has been made possible thanks to the effort and support of a dynamic community of developers, users and also several academic funding.

This version has mostly focus on stabilization, with some novelties nevertheless:
* the distributed computing feature of OpenMOLE are now very robust and efficient,
* the evolutionary algorithm part has matured and is usable to explore models from the console API,
* a new distributed environments (SLURM) is now available.

In the next versions:
* the graphical interface will be multi-user, web based and run in the browser,
* new environments will be provided (Condor, SGE),
* advanced methods such as genetic algorithm will be usable from the graphical interface,
* it will be possible to generate console scripts from a graphical workflow,
* bootstrapping methods that quickly and automatically embed your models in OpenMOLE will be implemented.

The OpenMOLE team

Intensive computing for the Social Sciences

Workshop organized around Intensive Computing in Social Sciences at the Complex Systems Institute in Paris, May 21st, from 10:00 am to 5:00 pm, 113 rue Nationale, Paris 13th, France.

Free but necessary registration : arnaud.banos@parisgeo.cnrs.fr

 

Preliminary Programme

> 10:00-10:30. Introduction : Patrice Bourdelais, Head of INSHS, CNRS

Presentation of the ERC GeoDiverCity : Denise Pumain, UMR Géographie-Cités

Presentation of the Complex Systems Institute : David Chavalarias, UMR CAMS

> 10:30- 11:30. OpenMOLE and its uses in Social Sciences

The OpenMOLE plateform, presentation and tutorial : Romain Reuillon and Mathieu Leclaire, ERC GeoDiverCity / ISC-PIF

A collective and interdisciplininary approach of geographical modeling around OpenMOLE : Paul Chapron, Clémentine Cottineau, Sébastien Rey Coyrehourcq, Clara Schmitt, ERC GeoDiverCity / UMR Géographie-Cités

> 11:30-12:30. Questions and discussion

> 2:00-4:00. “Regards croisés”

Big data and intensive computing : The Social Sciences in revolution ? : David Chavalarias, ISC-PIF

Equipex Matrice : Denis Peschanski, CNRS/Université Paris 1 (to be confirmed)

The “Run My Code” experiment, Christophe Perignon, HEC Paris (to be confirmed)

The MEXICO network : Robert Faivre, INRA

The interdisciplinary MAPS network : Marion Amalric, UMR CITERES

The SimTools network : Patrick Taillandier, UMR Idées

The research group GDR Modys : Xavier Rodier, UMR CITERES

> 4:00-5:00. Discussion : Modeling and intensive computing in Social Sciences

Michel Audiffren (GIS Réseau National des MSH), David Chavalarias (ISC-PIF), Guillaume Deffuant (IRSTEA), Catherine Garbay (IMAG), Michel Gollac (CREST), Thérèse Libourel (LIRMM), Anne Ruas (IFFSTAR), Françoise Thibault (Alliance Athena), Hervé Zwirn (CVT Alliance Athéna)