Pub Date : 2012-01-01DOI: 10.3929/ETHZ-A-007313727
Stefan Heule, Ioannis T. Kassios, Peter Müller, Alexander J. Summers
Abstract predicates are the primary abstraction mechanism for program logics based on access permissions, such as separation logic and implicit dynamic frames. In addition to abstract predicates, it is often useful to also support classical abstraction functions, for instance, to encode side-effect free methods of the program and use them in specifications. However, combining abstract predicates and abstraction functions in a verification condition generator leads to subtle interactions, which complicate reasoning about heap modifications. Such complications may compromise soundness or cause divergence of the prover in the context of automated verification. In this paper, we present an encoding of abstract predicates and abstraction functions in the verification condition generator Boogie. Our encoding is sound and handles recursion in a way that is suitable for automatic verification using SMT solvers. It is implemented in the automatic verifier Chalice.
{"title":"Verification Condition Generation for Permission Logics with Abstraction Functions","authors":"Stefan Heule, Ioannis T. Kassios, Peter Müller, Alexander J. Summers","doi":"10.3929/ETHZ-A-007313727","DOIUrl":"https://doi.org/10.3929/ETHZ-A-007313727","url":null,"abstract":"Abstract predicates are the primary abstraction mechanism for program logics based on access permissions, such as separation logic and implicit dynamic frames. In addition to abstract predicates, it is often useful to also support classical abstraction functions, for instance, to encode side-effect free methods of the program and use them in specifications. However, combining abstract predicates and abstraction functions in a verification condition generator leads to subtle interactions, which complicate reasoning about heap modifications. Such complications may compromise soundness or cause divergence of the prover in the context of automated verification. In this paper, we present an encoding of abstract predicates and abstraction functions in the verification condition generator Boogie. Our encoding is sound and handles recursion in a way that is suitable for automatic verification using SMT solvers. It is implemented in the automatic verifier Chalice.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90715650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-11-01DOI: 10.3929/ETHZ-A-006742278
Simon Peter, Andrew Baumann, Zachary Anderson, Timothy Roscoe
The hardware trend toward higher core counts will likely result in a dynamic, bursty and interactive mix of parallel applications in personal and server computing. We investigate whether gang scheduling can provide performance benefits for applications in this scenario. We present a systematic study of the conditions under which gang scheduling might be better than classical general-purpose OS scheduling, and derive a set of necessary conditions on the workload. We find that these conditions are rarely met today, except in a small subset of workloads, for which we give an example. However, we propose that this subset is potentially important in the future, if (for example) parallel algorithms become increasingly used for real-time computer-human interaction.
{"title":"Gang scheduling istn't worth it ... yet","authors":"Simon Peter, Andrew Baumann, Zachary Anderson, Timothy Roscoe","doi":"10.3929/ETHZ-A-006742278","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006742278","url":null,"abstract":"The hardware trend toward higher core counts will likely result in a dynamic, bursty and interactive mix of parallel applications in personal and server computing. We investigate whether gang scheduling can provide performance benefits for applications in this scenario. We present a systematic study of the conditions under which gang scheduling might be better than classical general-purpose OS scheduling, and derive a set of necessary conditions on the workload. We find that these conditions are rarely met today, except in a small subset of workloads, for which we give an example. However, we propose that this subset is potentially important in the future, if (for example) parallel algorithms become increasingly used for real-time computer-human interaction.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83223049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-01DOI: 10.3929/ETHZ-A-007313689
Martin Hentschel, Maxim N. Grinev, Donald Kossmann
Social communication features on most of today’s largest websites require propagating the data inside the database/key-value store leading to massive data flows. In this paper we study alternative architectures to build data flows using distributed key-value stores. We compare programming model, execution model, failure model, and scalability highlighting a problem of the state-of-the-art architecture based on an external queue: non-optimal resource utilization. As part of this study, we propose an optimization of this approach by integrating queues into the key-value store. It results in better resource utilization and, thus, more cost-effective scalability; as well as easier programmability and lower maintenance cost. Our experimental study confirms these findings.
{"title":"Building Data Flows Using Distributed Key-Value Stores","authors":"Martin Hentschel, Maxim N. Grinev, Donald Kossmann","doi":"10.3929/ETHZ-A-007313689","DOIUrl":"https://doi.org/10.3929/ETHZ-A-007313689","url":null,"abstract":"Social communication features on most of today’s largest websites require propagating the data inside the database/key-value store leading to massive data flows. In this paper we study alternative architectures to build data flows using distributed key-value stores. We compare programming model, execution model, failure model, and scalability highlighting a problem of the state-of-the-art architecture based on an external queue: non-optimal resource utilization. As part of this study, we propose an optimization of this approach by integrating queues into the key-value store. It results in better resource utilization and, thus, more cost-effective scalability; as well as easier programmability and lower maintenance cost. Our experimental study confirms these findings.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88165398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes how we modeled and solved the DEBS’11 Grand Challenge of implementing a social network game using event processing technology. We first present an automaton-based model that we used to capture the game semantics. Then we summarize three different approaches we investigated to implement this automaton together with their evaluations. Finally, we provide a discussion of our observations and lessons learned as a result of this study.
Pub Date : 2011-06-01DOI: 10.3929/ETHZ-A-006519144
S. Krug
We consider the beta-metric traveling salesman problem (Delta-beta-TSP), i.e., the TSP restricted to input instances satisfying the beta-triangle inequality c({v,w}) <= beta * (c{v,u} + c{u,w}), for any three vertices u,v,w. The well-known path matching Christofides algorithm (PMCA) provides an approximation ratio of 3/2 * beta^2 and is the best known algorithm in the range 1 <= beta <= 2. We show that this upper bound is tight by providing a worst-case example. This example can also be used to show the tightness of the upper bound for the PMCA variants for the Hamiltonian path problem with zero and one prespecified endpoints. For two prespecified endpoints, we cannot reuse the example, but we construct another worst-case example to show the tightness of the upper bound also in this case. Furthermore, we establish improved lower bounds for an approximation algorithm for the metric Hamiltonian path problem as well as for two approximation algorithms for the metric TSP reoptimization problem.
{"title":"Analysis of approximation algorithms for the traveling salesman problem in near-metric graphs","authors":"S. Krug","doi":"10.3929/ETHZ-A-006519144","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006519144","url":null,"abstract":"We consider the beta-metric traveling salesman problem (Delta-beta-TSP), i.e., the TSP restricted to input instances satisfying the beta-triangle inequality c({v,w}) <= beta * (c{v,u} + c{u,w}), for any three vertices u,v,w. The well-known path matching Christofides algorithm (PMCA) provides an approximation ratio of 3/2 * beta^2 and is the best known algorithm in the range 1 <= beta <= 2. We show that this upper bound is tight by providing a worst-case example. This example can also be used to show the tightness of the upper bound for the PMCA variants for the Hamiltonian path problem with zero and one prespecified endpoints. For two prespecified endpoints, we cannot reuse the example, but we construct another worst-case example to show the tightness of the upper bound also in this case. Furthermore, we establish improved lower bounds for an approximation algorithm for the metric Hamiltonian path problem as well as for two approximation algorithms for the metric TSP reoptimization problem.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85048340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-04-01DOI: 10.3929/ETHZ-A-006528721
D. Basin, C. Cremers
This report provides a security evaluation of the authentication protocol families described in parts 2, 3, and 4 of the ISO-IEC 9798 standard. Our analysis includes formal models of the protocols and their security properties, an analysis of existing attacks and evaluations, a security analysis of the formal protocol models, and a list of recommendations.
{"title":"Evaluation of ISO/IEC 9798 Protocols","authors":"D. Basin, C. Cremers","doi":"10.3929/ETHZ-A-006528721","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006528721","url":null,"abstract":"This report provides a security evaluation of the authentication protocol families described in parts 2, 3, and 4 of the ISO-IEC 9798 standard. Our analysis includes formal models of the protocols and their security properties, an analysis of existing attacks and evaluations, a security analysis of the formal protocol models, and a list of recommendations.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89043925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-01-01DOI: 10.3929/ETHZ-A-006903069
Michela Pedroni, M. Oriol, B. Meyer
One of the foremost issues for instructors of "Introduction to Programming" or "CS1" courses is the diversity of students' backgrounds { on one end of the range, a signicant portion of students start their computing degree without prior programming expertise, while on the other end, many students have even worked in a job where programming was a substantial part. This diversity makes it dicult to adapt programming instruction to students' prior experience. The present article describes students' programming and computing experience when entering the ETH Computer Science bachelor program. It is based on the data of over 900 ETH students participating in the study in the past seven years and 77 students from University of York answering the questionnaire in 2008. The article reports on the analysis of changes over the years, presents a comparison between the data of ETH and York, and describes the pedagogical implications for courses and textbooks.
{"title":"The prior experience of entering CS students","authors":"Michela Pedroni, M. Oriol, B. Meyer","doi":"10.3929/ETHZ-A-006903069","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006903069","url":null,"abstract":"One of the foremost issues for instructors of \"Introduction to Programming\" or \"CS1\" courses is the diversity of students' backgrounds { on one end of the range, a signicant portion of students start their computing degree without prior programming expertise, while on the other end, many students have even worked in a job where programming was a substantial part. This diversity makes it dicult to adapt programming instruction to students' prior experience. The present article describes students' programming and computing experience when entering the ETH Computer Science bachelor program. It is based on the data of over 900 ETH students participating in the study in the past seven years and 77 students from University of York answering the questionnaire in 2008. The article reports on the analysis of changes over the years, presents a comparison between the data of ETH and York, and describes the pedagogical implications for courses and textbooks.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"85 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81094755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-01-01DOI: 10.3929/ETHZ-A-007313562
Stefan Hildenbrand, Donald Kossmann, Tahmineh Sanamrad, Carsten Binnig, Franz Faerber, J. Woehler
This paper explores a new encryption technique called POP. POP addresses the need to encrypt databases in the cloud and to execute complex SQL queries on the encrypted data efficiently. POP can be configured to meet different privacy requirements and attacker scenarios. Two such scenarios, referred to as domain attack and frequency attack, are studied in detail in this paper. Privacy and performance experiments conducted using the TPC-H benchmark show that POP makes it indeed possible to achieve good privacy with affordable performance overheads in many cases.
{"title":"Query Processing on Encrypted Data in the Cloud by","authors":"Stefan Hildenbrand, Donald Kossmann, Tahmineh Sanamrad, Carsten Binnig, Franz Faerber, J. Woehler","doi":"10.3929/ETHZ-A-007313562","DOIUrl":"https://doi.org/10.3929/ETHZ-A-007313562","url":null,"abstract":"This paper explores a new encryption technique called POP. POP addresses the need to encrypt databases in the cloud and to execute complex SQL queries on the encrypted data efficiently. POP can be configured to meet different privacy requirements and attacker scenarios. Two such scenarios, referred to as domain attack and frequency attack, are studied in detail in this paper. Privacy and performance experiments conducted using the TPC-H benchmark show that POP makes it indeed possible to achieve good privacy with affordable performance overheads in many cases.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83943712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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