Modelling a Distributed Data Acquisition System

This thesis discusses the formal modelling and verification of certain non-real-time aspects of correctness of a mission-critical distributed software system known as the ALICE Data Point Service (ADAPOS). The domain of this distributed system is data acquisition from a particle detector control system in experimental high energy particle physics research. ADAPOS is part of the upgrade effort of A Large Ion Collider Experiment (ALICE) at the European Organisation for Nuclear Research (CERN), near Geneva in France/Switzerland, for the third run of the Large Hadron Collider (LHC). ADAPOS is based on the publicly available ALICE Data Point Processing (ADAPRO) C++14 framework and works within the free and open source GNU/Linux ecosystem. The model checker Spin was chosen for modelling and verifying ADAPOS. The model focuses on the general specification of ADAPOS. It includes ADAPOS processes, a load generator process, and rudimentary interpretations for the network protocols used between the processes. For experimenting with different interpretations of the underlying network protocols and also for coping with the state space explosion problem, eight variants of the model were developed and studied. Nine Linear Temporal Logic (LTL) properties were defined for all those variants. Large numbers of states were covered during model checking even though the model turned out to have a reachable state space too large to fully exhaust. No counter-examples were found to safety properties. A significant amount of evidence hinting that ADAPOS seems to be safe, was obtained. Liveness properties and implementation-level verification among other possible research directions remain open

Model Checking a C++ Software Framework, a Case Study

This paper presents a case study on applying two model checkers, SPIN and DIVINE, to verify key properties of a C++ software framework, known as ADAPRO, originally developed at CERN. SPIN was used for verifying properties on the design level. DIVINE was used for verifying simple test applications that interacted with the implementation. Both model checkers were found to have their own respective sets of pros and cons, but the overall experience was positive. Because both model checkers were used in a complementary manner, they provided valuable new insights into the framework, which would arguably have been hard to gain by traditional testing and analysis tools only. Translating the C++ source code into the modeling language of the SPIN model checker helped to find flaws in the original design. With DIVINE, defects were found in parts of the code base that had already been subject to hundreds of hours of unit tests, integration tests, and acceptance tests. Most importantly, model checking was found to be easy to integrate into the workflow of the software project and bring added value, not only as verification, but also validation methodology. Therefore, using model checking for developing library-level code seems realistic and worth the effort.Comment: In Proceedings of the 27th ACM Joint European Software Engineering Conference and Symposium on the Foundations of Software Engineering (ESEC/FSE '19), August 26-30, 2019, Tallinn, Estonia. ACM, New York, NY, USA, 11 page

Public transport funding under pressure : Challenges, opportunities, and new pathways caused by the Covid-19 pandemic in Sweden

Covid-19 has affected the supply, demand, and image of public transport in unprecedented ways. This report aims to investigate the short- and long-term effects of Covid-19 on public transport and its funding models, with specific focus on the Swedish context. Three research questions are in focus: How does Covid-19 impact on revenues and costs for public transport? What measures have public transport agencies made in response to these challenges? How does changes or stability in public transport due to Covid-19, in the longer run impact on the possibility to reach regional political aims of sustainable transport? The research questions are approached with both quantitative and qualitative methods, including interviews and a scenario workshop with mobility actors in Sweden. The three Swedish metropolitan regions, Stockholm, Västra Götaland and Skåne, are used as cases.  The report shows very clearly how farebox revenues drastically decreased in all three regions, as many people listened to the recommendations from authorities to avoid public transport. At the same time, costs remained largely unchanged. This resulted in a widened gap between costs for operating the system, and revenues that could finance those costs. To compensate for the loss of ticket revenues, earmarked state contributions were introduced on several occasions on an ad-hoc basis. Even with state contributions, regional subsidies to public transport increased. The so-called cost-recovery ratio declined in unprecedented ways. Thus, the share of public subsidies coming from tax-money, both regional and national, increased.   The three regions responded in similar ways to the funding challenge, but with some variations. Region Skåne was the only region that downsized operations at an early stage to reduce costs, which caused some political turmoil. Stockholm and Västra Götaland decided to maintain operations unchanged. Increased problems with fare evasion added to the problem of reduced revenues. To meet changes in demand, with more people working from home, new tickets were introduced. Several other measures were implemented to reduce congestion and transmission of disease, such as dispersed school start and improved traffic information. Such measures can impact costs in the longer-term perspective if adopted at larger scale and over longer time.  Future implications of the pandemic on public transport and its funding are difficult to assess. The report includes an analysis based on four different scenarios developed within the project – “Downward spiral”, “Return”, “New mobility systems” and “Public transport as backbone”. The analysis indicates that he public transport actors in particular should try to avoid and be prepared to handle the scenario of “Downward spiral”, but also “Return” and “New mobility systems”, since these scenarios are judged to include difficulties.   Based on institutional theory, three more general reflections are made concerning the impact on future funding models. A first reflection is that the national level has stepped in as an important funder of public transport in Sweden. If demand for public transport remain on a significantly lower level compared to the pre-pandemic situation, continued national funding might be needed to prevent a development in line with the “Downward spiral” scenario. If so, national funding may be part of a new institutional equilibrium that influence power relations and actor’s behavior in the future.   A second observation is that the pandemic might change ideas about public transport’s role in society in ways that transform the existing institutions from within. A larger focus on individual, demand responsive solutions, and measures to reduce crowding will impact funding models. Increased working from home change the basic idea of a public transport system serving a rather fixed commuting behavior. More flexibility will be needed for public transport to remain relevant. We have already seen examples of institutional adjustments in ticket regimes, which is something that may continue at a larger scale.  A third reflection is that the widened funding gap change the cost-benefit equation in public transport. This may have repercussions for the institutional frameworks. In the “Downward spiral” scenario institutions may change mainly from within, with a shift from a focus on societal development and sustainability towards a more budget oriented way of thinking, with cost reductions, revenue maximization, increased ticket prices, and similar measures. To avoid such a development, the national level may need to take a more active role in funding, but also take a more active role as a “meta-governor” that steer the direction of public transport actors. The scenarios, “New mobility systems” and “Public transport as backbone” will require larger institutional makeovers where new funding models are needed to support other forms of shared transport modes. This may in more fundamental ways change the perception of what public transport is and how it should be funded.Covid-19 har påverkat såväl efterfrågan på som bilden av kollektivtrafiken på ett unikt sätt. Denna rapport undersöker effekterna av Covid-19 för kollektivtrafiken och dess finansieringsmodeller på både kort och längre sikt, med särskilt fokus på den svenska kontexten. Tre forskningsfrågor är i fokus: Hur påverkar Covid-19 intäkter och kostnader för kollektivtrafiken? Vilka åtgärder har kollektivtrafikmyndigheterna vidtagit som svar på finansiella utmaningar? Hur kan förändringar av kollektivtrafiken, till följd av Covid-19, påverka möjligheten att uppnå regionalpolitiska mål om hållbara transporter? Forskningsfrågorna hanteras med både kvantitativa och kvalitativa metoder, inklusive intervjuer och en workshop där olika scenarier analyserats med mobilitetsaktörer i Sverige. De tre svenska storstadsregionerna Stockholm, Västra Götaland och Skåne används som fall.  Rapporten visar tydligt hur biljettintäkterna drastiskt minskade i alla tre regionerna, eftersom många resenärer följt myndigheternas rekommendationer att undvika kollektivtrafik. Samtidigt har kostnaderna för kollektivtrafiken varit i stort sett oförändrade. Detta resulterade i ett ökat gap mellan kostnader för driften av kollektivtrafiken och intäkterna som behövs för att finansiera kostnaderna. För att kompensera för förlusten av biljettintäkter infördes öronmärkta statliga bidrag vid flera tillfällen på ad hoc-basis. Trots statliga bidrag ökade även regionala subventioner till kollektivtrafiken. Således ökade andelen både nationella och regionala subventioner till kollektivtrafiken. Den så kallade kostnadstäckningsgraden minskade dramatiskt.  De tre regionerna svarade på finansieringsutmaningen på liknande sätt, men med vissa variationer. Region Skåne var den enda regionen som i ett tidigt skede minskade utbudet för att minska kostnaderna, vilket orsakade viss politisk diskussion. Stockholm och Västra Götaland beslutade att behålla utbudet oförändrat. Ökade problem med plankning bidrog ytterligare till minskade intäkter. För att möta efterfrågeförändringen, med fler resenärer som arbetade hemifrån, introducerades nya biljettyper. Andra åtgärder genomfördes i syfte att minska trängsel och smittorisk, till exempel spridda skolstarter och förbättrad trafikinformation. Sådana åtgärder kan påverka kostnaderna på längre sikt om de genomförs i större skala och över längre tidsperioder.  Framtida konsekvenser av pandemin för kollektivtrafiken och dess finansiering är svåra att bedöma. Rapporten innehåller en analys baserad på fyra olika scenarier som utvecklats inom projektet - "Nedåtgående spiral", "Återgång", "Nya mobilitetssystem" och "Kollektivtrafik som ryggrad". Analysen indikerar att kollektivtrafikaktörerna särskilt bör försöka undvika och vara beredda att hantera scenariot med "Nedåtgående spiral", men också "Återgång" och "Nya mobilitetssystem", eftersom dessa scenarion bedöms innehålla svårigheter.  Baserat på institutionell teori görs i rapporten tre övergripande reflektioner om effekterna på framtida finansieringsmodeller. En första observation är att den nationella nivån har gått in som en viktig finansiär för kollektivtrafiken i Sverige. Om efterfrågan på kollektivtrafik förblir på en betydligt lägre nivå, jämfört med situationen före pandemin, kan fortsatt nationell finansiering behövas för att förhindra en utveckling i linje med "Nedåtgående spiral" -scenariot. I så fall kan nationell finansiering vara en del av en ny institutionell jämvikt som påverkar maktrelationer och aktörers beteende i framtiden.  En andra observation är att pandemin kan förändra idéer om kollektivtrafikens roll i samhället på ett sätt som förändrar de befintliga institutionerna inifrån. Ett större fokus på individuella, efterfrågestyrda lösningar och åtgärder för att minska trängsel kommer att påverka finansieringsmodellerna. Ökat arbete hemifrån förändrar grundtanken om ett kollektivtrafiksystem som servar ett ganska fast pendlingsbeteende. Mer flexibilitet kommer att krävas för att kollektivtrafiken ska förbli relevant. Vi har redan sett exempel på justeringar i biljettutbudet, vilket är något som kan fortsätta i större skala.  En tredje reflektion är att det ökade finansieringsgapet ändrar kostnads-nytto-ekvationen inom kollektivtrafiken. Detta kan få konsekvenser för de institutionella ramarna. I scenariot "Nedåtgående spiral" kan institutioner förändras huvudsakligen inifrån, med en förskjutning från fokus på samhällsutveckling och hållbarhet mot ett mer budgetorienterat tankesätt, med kostnadsminskningar, intäktsmaximering, ökade biljettpriser och liknande åtgärder. För att undvika en sådan utveckling kan den nationella nivån behöva ta en mer aktiv roll i finansieringen, men också ta en mer aktiv roll som en ”meta-governor” med ambitionen att påverka riktningen för kollektivtrafikens aktörer. Scenarierna, "Nya mobilitetssystem" och "Kollektivtrafik som ryggrad" kommer att kräva större institutionella omställningar där nya finansieringsmodeller behövs för att stödja andra former av delade transportsätt. Detta kan på mer grundläggande sätt förändra uppfattningen om vad kollektivtrafik är och hur den ska finansieras

ADAPOS: An architecture for publishing ALICE DCS conditions data

ALICE Data Point Service (ADAPOS) is a software architecture being developed for the RUN3 period of LHC, as a part of the effort to transmit conditions data from ALICE Detector Control System (DCS) to Event Processing Network (EPN), for distributed processing. The key processes of ADAPOS, Engine and Terminal, run on separate machines, facing different networks. Devices connected to DCS publish their state as DIM services. Engine gets updates to the services, and converts them into a binary stream. Terminal receives it over 0MQ, and maintains an image of the DCS state. It sends copies of the image, at regular intervals, over another 0MQ connection, to a readout process of ALICE Data Acquisition.ALICE Data Point Service (ADAPOS) is a software architecture being developed for the Run 3 period of LHC, as a part of the effort to transmit conditions data from ALICE Detector Control System (DCS) to GRID, for distributed processing. ADAPOS uses Distributed Information Management (DIM), 0MQ, and ALICE Data Point Processing Framework (ADAPRO). DIM and 0MQ are multi-purpose application-level network protocols. DIM and ADAPRO are being developed and maintained at CERN. ADAPRO is a multi-threaded application framework, supporting remote control, and also real-time features, such as thread affinities, records aligned with cache line boundaries, and memory locking. ADAPOS and ADAPRO are written in C++14 using OSS tools, Pthreads, and Linux API. The key processes of ADAPOS, Engine and Terminal, run on separate machines, facing different networks. Devices connected to DCS publish their state as DIM services. Engine gets updates to the services, and converts them into a binary stream. Terminal receives it over 0MQ, and maintains an image of the DCS state. It sends copies of the image, at regular intervals, over another 0MQ connection, to a readout process of ALICE Data Acquisition

How low-cost devices can help on the way to ALICE upgrade

Cheap, ready to install and simple to configure, minicomputer and microcontroller boards have been in use in ALICE for a few years for specific, non-critical tasks, like integrating the environment sensors network in the experimental site, and to monitor and analyse clock signals. These systems have also been installed inside the ALICE experiment, in the presence of magnetic field and radiation, and subjected to a functionality test. While the major part of these devices proved to work correctly even under the experiment conditions, finally some weaknesses were revealed, thus excluding this class of devices from usage in the production setup. They have also played a role in the realization of scaled systems for the ALICE upgrade. With them, we have been able to simulate the presence of Front-End cards which are not yet available, allowing to proceed in the development of the software framework, of libraries and interfaces, in parallel with the production and validation of the hardware components. Being off-the-shelf and available everywhere in the world, they can be installed in remote institutes and laboratories participating to the collaboration. Some of the systems have been realised by students and trainees hosted at CERN for short periods of time. As well as being cheap and easy to procure, they proved to be a great didactic tool, allowing young collaborators to realise a complete system from scratch, integrate into a complex infrastructure and get a hands-on approach to modern control systems.The ambitious upgrade plan of the ALICE experiment expects a complete redesign of its data flow after the LHC shutdown scheduled for 2019, for which new electronics modules are being developed in the collaborating institutes. Access to prototypes is at present very limited and full scale prototypes are expected only close to the installation date. To overcome the lack of realistic HW, the ALICE DCS team built small-scale prototypes based on low-cost commercial components (Arduino, Raspberry PI), equipped with environmental sensors, and installed in the experiment areas around and inside the ALICE detector. Communication and control software was developed, based on the architecture proposed for the future detectors, including CERN JCOP FW and ETM WINCC OA. Data provided by the prototypes has been recorded for several months, in presence of beam and magnetic field. The challenge of the harsh environment revealed some insurmountable weaknesses, thus excluding this class of devices from usage in a production setup. They did prove, however, to be robust enough for test purposes, and are still a realistic test-bed for developers while the production of final electronics is continuing