{"title":"Session details: Session 4","authors":"N. Vaidya","doi":"10.1145/3246718","DOIUrl":"https://doi.org/10.1145/3246718","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131835763","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}
We devise a technique for augmenting shared objects in the standard n-process shared memory model with a linearizable Write{} operation, using bounded space and optimal worst-case step complexity. We provide a transformation of any shared object SW supporting only sequential Write{} operations into an object $W$ that supports concurrent Write{} operations. This transformation requires O(n2) SW objects and O(n2) O(log n)-bit registers, and each method (including Write{}) has, up to a constant additive term, the same time complexity as the corresponding method on object $SW$. Our implementation is deterministic, wait-free, and uses only shared registers (supporting atomic read and write operations). To the best of our knowledge, similarly efficient general constructions are not known even if stronger primitives such as CAS or LL/SC are available. Applying our transformation, we obtain an implementation of a k-word register from O(n2⋅ k) single-word registers. As another application we can transform randomized one-time TAS objects (e.g., randomized wait-free implementations that use a bounded number of registers [8,9]), into long-lived ones using also a bounded number of registers. The transformation preserves the time complexity of TaS{} operations and allows resets in constant worst-case time. Our transformation employs a novel memory reclamation technique, which can replace Hazard Pointers [20] and is more efficient.
{"title":"Making objects writable","authors":"Zahra Aghazadeh, W. Golab, Philipp Woelfel","doi":"10.1145/2611462.2611483","DOIUrl":"https://doi.org/10.1145/2611462.2611483","url":null,"abstract":"We devise a technique for augmenting shared objects in the standard n-process shared memory model with a linearizable Write{} operation, using bounded space and optimal worst-case step complexity. We provide a transformation of any shared object SW supporting only sequential Write{} operations into an object $W$ that supports concurrent Write{} operations. This transformation requires O(n2) SW objects and O(n2) O(log n)-bit registers, and each method (including Write{}) has, up to a constant additive term, the same time complexity as the corresponding method on object $SW$. Our implementation is deterministic, wait-free, and uses only shared registers (supporting atomic read and write operations). To the best of our knowledge, similarly efficient general constructions are not known even if stronger primitives such as CAS or LL/SC are available. Applying our transformation, we obtain an implementation of a k-word register from O(n2⋅ k) single-word registers. As another application we can transform randomized one-time TAS objects (e.g., randomized wait-free implementations that use a bounded number of registers [8,9]), into long-lived ones using also a bounded number of registers. The transformation preserves the time complexity of TaS{} operations and allows resets in constant worst-case time. Our transformation employs a novel memory reclamation technique, which can replace Hazard Pointers [20] and is more efficient.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116871038","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}
Lock-free concurrent algorithms guarantee that some concurrent operation will always make progress in a finite number of steps. Yet programmers prefer to treat concurrent code as if it were wait-free, guaranteeing that all operations always make progress. Unfortunately, designing wait-free algorithms is generally a very complex task, and the resulting algorithms are not always efficient. While obtaining efficient wait-free algorithms has been a long-time goal for the theory community, most non-blocking commercial code is only lock-free. This paper suggests a simple solution to this problem. We show that, for a large class of lock-free algorithms, under scheduling conditions which approximate those found in commercial hardware architectures, lock-free algorithms behave as if they are wait-free. In other words, programmers can keep on designing simple lock-free algorithms instead of complex wait-free ones, and in practice, they will get wait-free progress. Our main contribution is a new way of analyzing a general class of lock-free algorithms under a stochastic scheduler. Our analysis relates the individual performance of processes with the global performance of the system using Markov chain lifting between a complex per-process chain and a simpler system progress chain. We show that lock-free algorithms are not only wait-free with probability 1, but that in fact a general subset of lock-free algorithms can be closely bounded in terms of the average number of steps required until an operation completes. To the best of our knowledge, this is the first attempt to analyze progress conditions, typically stated in relation to a worst case adversary, in a stochastic model capturing their expected asymptotic behavior.
{"title":"Brief announcement: are lock-free concurrent algorithms practically wait-free?","authors":"Dan Alistarh, K. Censor-Hillel, N. Shavit","doi":"10.1145/2611462.2611502","DOIUrl":"https://doi.org/10.1145/2611462.2611502","url":null,"abstract":"Lock-free concurrent algorithms guarantee that some concurrent operation will always make progress in a finite number of steps. Yet programmers prefer to treat concurrent code as if it were wait-free, guaranteeing that all operations always make progress. Unfortunately, designing wait-free algorithms is generally a very complex task, and the resulting algorithms are not always efficient. While obtaining efficient wait-free algorithms has been a long-time goal for the theory community, most non-blocking commercial code is only lock-free. This paper suggests a simple solution to this problem. We show that, for a large class of lock-free algorithms, under scheduling conditions which approximate those found in commercial hardware architectures, lock-free algorithms behave as if they are wait-free. In other words, programmers can keep on designing simple lock-free algorithms instead of complex wait-free ones, and in practice, they will get wait-free progress. Our main contribution is a new way of analyzing a general class of lock-free algorithms under a stochastic scheduler. Our analysis relates the individual performance of processes with the global performance of the system using Markov chain lifting between a complex per-process chain and a simpler system progress chain. We show that lock-free algorithms are not only wait-free with probability 1, but that in fact a general subset of lock-free algorithms can be closely bounded in terms of the average number of steps required until an operation completes. To the best of our knowledge, this is the first attempt to analyze progress conditions, typically stated in relation to a worst case adversary, in a stochastic model capturing their expected asymptotic behavior.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"132 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121773303","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}
We improve upon an existing non-blocking implementation of a binary search tree from single-word compare-and-swap instructions. We show that the worst-case amortized step complexity of performing a Find, Insert or Delete operation op on the tree is O(h(op)+c(op)) where h(op) is the height of the tree at the beginning of op and c(op) is the maximum number of operations accessing the tree at any one time during op. This is the first bound on the complexity of a non-blocking implementation of a search tree.
{"title":"The amortized complexity of non-blocking binary search trees","authors":"Faith Ellen, P. Fatourou, J. Helga, E. Ruppert","doi":"10.1145/2611462.2611486","DOIUrl":"https://doi.org/10.1145/2611462.2611486","url":null,"abstract":"We improve upon an existing non-blocking implementation of a binary search tree from single-word compare-and-swap instructions. We show that the worst-case amortized step complexity of performing a Find, Insert or Delete operation op on the tree is O(h(op)+c(op)) where h(op) is the height of the tree at the beginning of op and c(op) is the maximum number of operations accessing the tree at any one time during op. This is the first bound on the complexity of a non-blocking implementation of a search tree.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131512893","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}
Cryptography and distributed computation have been very successful in advancing the study of interaction of distinct computing agents. Moreover, both fields have been very successful in conversing with each other, sharing models and techniques. Notably, they both model agents as being either 'good' (i.e., following their prescribed programs) or 'bad' (i.e., deviating from their prescribed program, by stopping, by acting maliciously, or even by coordinating their malicious strategies). I believe however, that we have been neglecting a fundamental ingredient, UTILITY, which has long been recognized and studied by another scientific field, game theory, and in particular by a beautiful subfield of it, mechanism design. Mechanism design aims at obtaining a desired outcome by engineering a game that, rationally played, yields a desired outcome. In such games, multiple players interact very much as in a cryptographic/distributed protocol. But here players are not good or malicious. Rather, every player is RATIONAL, that is, always acts so as to maximize HIS OWN utility. I believe that properly incorporating utility/rationality in our models will dramatically increase our range of action. Viceversa, mechanism design stands to gain a lot by properly incorporating cryptographic/distributed notions and techniques. In particular, rational players may, by colluding (and making side-payments to one another), increase their utilities. And they too value privacy, which may indeed represent their strategic interests in unforeseen and not yet modeled interactions. Thus, privacy and collusion can disrupt the intended course of an engineered game, and ultimately prevent a desired outcome from being achieved. Mechanism design has been only moderately successful in protecting against collusion, has largely ignored privacy, and might gain precious resiliency by taking into consideration our notions and techniques. In sum, there is an opportunity for cryptography, distributed computation, and mechanism design to join forces to study more general and accurate models of interaction, and to design more realistic and resilient protocols that simultaneously take into account utility, collusion, and privacy. No sufficiently complex and sufficiently large system, no organism can successfully work or merely sustain its existence without recognizing and harmonizing these basic forces. To be successful, this designing effort will require a good deal of modeling and the development of new conceptual frameworks. It will require open minds and open hearts, so as to leverage past and successful scientific experiences, without being trapped or confined by them. There is the promise of a great deal of fun, challenge, and excitement, and we must recruit as much talent as possible to this effort. As a concrete, simple, and hopefully provocative example, I will describe a (quite) resilient mechanism, designed by me and Jing Chen, for achieving a (quite) alternative revenue benchmark in un
{"title":"Rational and resilient protocols","authors":"S. Micali","doi":"10.1145/2611462.2611516","DOIUrl":"https://doi.org/10.1145/2611462.2611516","url":null,"abstract":"Cryptography and distributed computation have been very successful in advancing the study of interaction of distinct computing agents. Moreover, both fields have been very successful in conversing with each other, sharing models and techniques. Notably, they both model agents as being either 'good' (i.e., following their prescribed programs) or 'bad' (i.e., deviating from their prescribed program, by stopping, by acting maliciously, or even by coordinating their malicious strategies). I believe however, that we have been neglecting a fundamental ingredient, UTILITY, which has long been recognized and studied by another scientific field, game theory, and in particular by a beautiful subfield of it, mechanism design. Mechanism design aims at obtaining a desired outcome by engineering a game that, rationally played, yields a desired outcome. In such games, multiple players interact very much as in a cryptographic/distributed protocol. But here players are not good or malicious. Rather, every player is RATIONAL, that is, always acts so as to maximize HIS OWN utility. I believe that properly incorporating utility/rationality in our models will dramatically increase our range of action. Viceversa, mechanism design stands to gain a lot by properly incorporating cryptographic/distributed notions and techniques. In particular, rational players may, by colluding (and making side-payments to one another), increase their utilities. And they too value privacy, which may indeed represent their strategic interests in unforeseen and not yet modeled interactions. Thus, privacy and collusion can disrupt the intended course of an engineered game, and ultimately prevent a desired outcome from being achieved. Mechanism design has been only moderately successful in protecting against collusion, has largely ignored privacy, and might gain precious resiliency by taking into consideration our notions and techniques. In sum, there is an opportunity for cryptography, distributed computation, and mechanism design to join forces to study more general and accurate models of interaction, and to design more realistic and resilient protocols that simultaneously take into account utility, collusion, and privacy. No sufficiently complex and sufficiently large system, no organism can successfully work or merely sustain its existence without recognizing and harmonizing these basic forces. To be successful, this designing effort will require a good deal of modeling and the development of new conceptual frameworks. It will require open minds and open hearts, so as to leverage past and successful scientific experiences, without being trapped or confined by them. There is the promise of a great deal of fun, challenge, and excitement, and we must recruit as much talent as possible to this effort. As a concrete, simple, and hopefully provocative example, I will describe a (quite) resilient mechanism, designed by me and Jing Chen, for achieving a (quite) alternative revenue benchmark in un","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132325260","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}
{"title":"Session details: Session 13","authors":"Luís Rodrigues","doi":"10.1145/3246727","DOIUrl":"https://doi.org/10.1145/3246727","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121994233","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}
Joshua Baron, Karim M. El Defrawy, Joshua Lampkins, R. Ostrovsky
In PODC 1991 Ostrovsky and Yung [35] introduced the proactive security model, where corruptions spread throughout the network, analogous to the spread of a virus or a worm. PODC 2006 distinguished lecture by Danny Dolev, that also appears in the PODC06 proceedings, lists the above work as one of PODC's "Century Papers at the First Quarter-Century Milestone" [22]. At the very center of this work is the notion of proactive secret sharing schemes. Secret sharing schemes allow a dealer to distribute a secret among a group of parties such that while the group of parties jointly possess the secret, no sufficiently small subset of the parties can learn any information about the secret. The secret can be reconstructed only when a sufficient number of shares are combined together. Most secret sharing schemes assume that an adversary can only corrupt some fixed number of the parties over the entire lifetime of the secret; such a model is unrealistic in the case where over a long enough period of time, an adversary can eventually corrupt all parties or a large enough fraction that exceeds such a threshold. More specifically, in the proactive security model, the adversary is not limited in the number of parties it can corrupt, but rather in the rate of corruption with respect to a "rebooting" rate. Ostrovsky and Yung proposed the first proactive secret sharing scheme, which received a lot of follow-up attention. In the same paper, Ostrovsky and Yung also showed that constructing a general purpose secure multiparty computation (MPC) protocol in the proactive security model is feasible as long as the rate of corruption is a constant fraction of the parties. Their result, however, was shown only for stand-alone security and incurred a large polynomial communication overhead for each gate of the computation. Following the initial work defining the proactive security model, numerous cryptographic primitives and distributed protocols have been adapted to the proactive security model, such as proactively secure threshold encryption, proactive Byzantine agreement, proactive key management, proactive digital signatures, and many others. All these results use proactive secret sharing schemes. In this paper, we introduce a new "packed" proactive secret sharing (PPSS) scheme, where the amortized communication and the amortized computational cost of maintaining each individual secret is optimal (e.g., a constant rate), resolving a long standing problem in this area. Assuming secure point-to-point channels and authenticated, reliable broadcast over a synchronous network, our PPSS scheme can tolerate a 1/3-ε (resp. 1/2-ε) corruption rate against a malicious adversary, and is perfectly (resp. statistically) UC-secure, whereas all previous proactive secret sharing schemes have been secure under cryptographic assumptions only. As an application of our PPSS scheme, we show how to construct a proactive multiparty computation (PMPC) protocol with the same threshold as the PPSS s
{"title":"How to withstand mobile virus attacks, revisited","authors":"Joshua Baron, Karim M. El Defrawy, Joshua Lampkins, R. Ostrovsky","doi":"10.1145/2611462.2611474","DOIUrl":"https://doi.org/10.1145/2611462.2611474","url":null,"abstract":"In PODC 1991 Ostrovsky and Yung [35] introduced the proactive security model, where corruptions spread throughout the network, analogous to the spread of a virus or a worm. PODC 2006 distinguished lecture by Danny Dolev, that also appears in the PODC06 proceedings, lists the above work as one of PODC's \"Century Papers at the First Quarter-Century Milestone\" [22]. At the very center of this work is the notion of proactive secret sharing schemes. Secret sharing schemes allow a dealer to distribute a secret among a group of parties such that while the group of parties jointly possess the secret, no sufficiently small subset of the parties can learn any information about the secret. The secret can be reconstructed only when a sufficient number of shares are combined together. Most secret sharing schemes assume that an adversary can only corrupt some fixed number of the parties over the entire lifetime of the secret; such a model is unrealistic in the case where over a long enough period of time, an adversary can eventually corrupt all parties or a large enough fraction that exceeds such a threshold. More specifically, in the proactive security model, the adversary is not limited in the number of parties it can corrupt, but rather in the rate of corruption with respect to a \"rebooting\" rate. Ostrovsky and Yung proposed the first proactive secret sharing scheme, which received a lot of follow-up attention. In the same paper, Ostrovsky and Yung also showed that constructing a general purpose secure multiparty computation (MPC) protocol in the proactive security model is feasible as long as the rate of corruption is a constant fraction of the parties. Their result, however, was shown only for stand-alone security and incurred a large polynomial communication overhead for each gate of the computation. Following the initial work defining the proactive security model, numerous cryptographic primitives and distributed protocols have been adapted to the proactive security model, such as proactively secure threshold encryption, proactive Byzantine agreement, proactive key management, proactive digital signatures, and many others. All these results use proactive secret sharing schemes. In this paper, we introduce a new \"packed\" proactive secret sharing (PPSS) scheme, where the amortized communication and the amortized computational cost of maintaining each individual secret is optimal (e.g., a constant rate), resolving a long standing problem in this area. Assuming secure point-to-point channels and authenticated, reliable broadcast over a synchronous network, our PPSS scheme can tolerate a 1/3-ε (resp. 1/2-ε) corruption rate against a malicious adversary, and is perfectly (resp. statistically) UC-secure, whereas all previous proactive secret sharing schemes have been secure under cryptographic assumptions only. As an application of our PPSS scheme, we show how to construct a proactive multiparty computation (PMPC) protocol with the same threshold as the PPSS s","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129771725","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}
{"title":"Session details: Session 9","authors":"Seth Gilbert","doi":"10.1145/3246723","DOIUrl":"https://doi.org/10.1145/3246723","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125427138","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}
A notion of a universal construction suited to distributed computing has been introduced by M. Herlihy in his celebrated paper "Wait-free synchronization" (ACM TOPLAS, 1991). A universal construction is an algorithm that can be used to wait-free implement any object defined by a sequential specification. Herlihy's paper shows that the basic system model, which supports only atomic read/write registers, has to be enriched with consensus objects to allow the design of universal constructions. The generalized notion of a k-universal construction has been recently introduced by Gafni and Guerraoui (CONCUR, 2011). A k-universal construction is an algorithm that can be used to simultaneously implement k objects (instead of just one object), with the guarantee that at least one of the k constructed objects progresses forever. While Herlihy's universal construction relies on atomic registers and consensus objects, a k-universal construction relies on atomic registers and k-simultaneous consensus objects (which have been shown to be computationally equivalent to k-set agreement objects in the read/write system model where any number of processes may crash). This paper significantly extends the universality results introduced by Herlihy and Gafni-Guerraoui. In particular, we present a k-universal construction which satisfies the following five desired properties, which are not satisfied by the previous k-universal construction: (1) among the k objects that are constructed, at least l objects (and not just one) are guaranteed to progress forever; (2) the progress condition for processes is wait-freedom, which means that each correct process executes an infinite number of operations on each object that progresses forever; (3) if one of the k constructed objects stops progressing, it stops in the same state at each process; (4) the proposed construction is contention-aware, which means that it uses only read/write registers in the absence of contention; and (5) it is indulgent with respect to the obstruction-freedom progress condition, which means that each process is able to complete any one of its pending operations on the k objects if all the other process hold still long enough. The proposed construction, which is based on new design principles, is called a (k,l)-universal construction. It uses a natural extension of k-simultaneous consensus objects, called (k,l)-simultaneous consensus objects ((k,l)-SC). Together with atomic registers, (k,l)-SC objects are shown to be necessary and sufficient for building a (k,l)-universal construction, and, in that sense, (k,l)-SC objects are (k,l)-universal.
{"title":"Brief announcement: distributed universality: contention-awareness; wait-freedom; object progress, and other properties","authors":"M. Raynal, J. Stainer, G. Taubenfeld","doi":"10.1145/2611462.2611503","DOIUrl":"https://doi.org/10.1145/2611462.2611503","url":null,"abstract":"A notion of a universal construction suited to distributed computing has been introduced by M. Herlihy in his celebrated paper \"Wait-free synchronization\" (ACM TOPLAS, 1991). A universal construction is an algorithm that can be used to wait-free implement any object defined by a sequential specification. Herlihy's paper shows that the basic system model, which supports only atomic read/write registers, has to be enriched with consensus objects to allow the design of universal constructions. The generalized notion of a k-universal construction has been recently introduced by Gafni and Guerraoui (CONCUR, 2011). A k-universal construction is an algorithm that can be used to simultaneously implement k objects (instead of just one object), with the guarantee that at least one of the k constructed objects progresses forever. While Herlihy's universal construction relies on atomic registers and consensus objects, a k-universal construction relies on atomic registers and k-simultaneous consensus objects (which have been shown to be computationally equivalent to k-set agreement objects in the read/write system model where any number of processes may crash). This paper significantly extends the universality results introduced by Herlihy and Gafni-Guerraoui. In particular, we present a k-universal construction which satisfies the following five desired properties, which are not satisfied by the previous k-universal construction: (1) among the k objects that are constructed, at least l objects (and not just one) are guaranteed to progress forever; (2) the progress condition for processes is wait-freedom, which means that each correct process executes an infinite number of operations on each object that progresses forever; (3) if one of the k constructed objects stops progressing, it stops in the same state at each process; (4) the proposed construction is contention-aware, which means that it uses only read/write registers in the absence of contention; and (5) it is indulgent with respect to the obstruction-freedom progress condition, which means that each process is able to complete any one of its pending operations on the k objects if all the other process hold still long enough. The proposed construction, which is based on new design principles, is called a (k,l)-universal construction. It uses a natural extension of k-simultaneous consensus objects, called (k,l)-simultaneous consensus objects ((k,l)-SC). Together with atomic registers, (k,l)-SC objects are shown to be necessary and sufficient for building a (k,l)-universal construction, and, in that sense, (k,l)-SC objects are (k,l)-universal.","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116057557","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}
{"title":"Session details: Session 1","authors":"J. Welch","doi":"10.1145/3246715","DOIUrl":"https://doi.org/10.1145/3246715","url":null,"abstract":"","PeriodicalId":186800,"journal":{"name":"Proceedings of the 2014 ACM symposium on Principles of distributed computing","volume":"2017 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121798018","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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