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Michel Raynal - One of the best experts on this subject based on the ideXlab platform.
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SIROCCO - A versatile STM protocol with invisible read operations that satisfies the virtual world Consistency Condition
Structural Information and Communication Complexity, 2010Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to design each process the application is made up of as a sequence of transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. Of course, for efficiency, a STM system has to allow transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can easily be weakened while still providing an STM system that satisfies causal Consistency, a Condition strictly weaker than virtual world Consistency.
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a versatile stm protocol with invisible read operations that satisfies the virtual world Consistency Condition
International Conference on Structural Information and Communication Complexity, 2009Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to design each process the application is made up of as a sequence of transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. Of course, for efficiency, a STM system has to allow transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can easily be weakened while still providing an STM system that satisfies causal Consistency, a Condition strictly weaker than virtual world Consistency.
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A versatile STM protocol with invisible read operations that satisfies the virtual world Consistency Condition
2009Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to decompose each sequential process the application is made up of into transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. For efficiency, a STM system allows transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can be weakened to satisfy the causal Consistency Condition (that is weaker than virtual world Consistency). Virtual world Consistency does not require the aborted transactions to agree on what they have seen. This is captured by the local vector clocks associated with each process and the vector timestamps associated with each object. From a comprehensive point of view, the paper addresses how the interplay of these local control informations allows the execution of a set of transactions to be provided with a global meaning.
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Normality: A Consistency Condition FOR CONCURRENT OBJECTS
Parallel Processing Letters, 1999Co-Authors: Vijay K. Garg, Michel RaynalAbstract:This paper is focused on concurrent objects (objects shared by concurrent processes). It introduces a Consistency Condition called Normality whose definition is based only on local orders of operations as perceived by processes and by objects. First we consider the model in which each operation is on exactly one object. In this model we show that a history is linearizable iff it is normal. However, the definition of Normality is less constraining in the sense that there are strictly more legal sequential histories which are considered equivalent to the given history when Normality is used. We next consider a more general model where operations can span multiple objects. In this model we show that Normality is strictly weaker than Linearizability, i.e., history may be normal but not linearizable. As Normality refers only to local orders (process order and object order) it appears to be well-suited to objects supported by asynchronous distributed systems and accessed by RPC-like mechanisms.
Glenn Barnich - One of the best experts on this subject based on the ideXlab platform.
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results on the wess zumino Consistency Condition for arbitrary lie algebras
arXiv: Mathematical Physics, 2002Co-Authors: Abdelilah Barkallil, Glenn Barnich, Christiane SchomblondAbstract:The so-called covariant Poincare lemma on the induced cohomology of the spacetime exterior derivative in the cohomology of the gauge part of the BRST differential is extended to cover the case of arbitrary, non reductive Lie algebras. As a consequence, the general solution of the Wess-Zumino Consistency Condition with a non trivial descent can, for arbitrary (super) Lie algebras, be computed in the small algebra of the 1 form potentials, the ghosts and their exterior derivatives. For particular Lie algebras that are the semidirect sum of a semisimple Lie subalgebra with an ideal, a theorem by Hochschild and Serre is used to characterize more precisely the cohomology of the gauge part of the BRST differential in the small algebra. In the case of an abelian ideal, this leads to a complete solution of the Wess-Zumino Consistency Condition in this space. As an application, the consistent deformations of 2+1 dimensional Chern-Simons theory based on iso(2,1) are rediscussed.
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Results on the Wess-Zumino Consistency Condition for arbitrary Lie algebras
Journal of Mathematical Physics, 2002Co-Authors: Abdelilah Barkallil, Glenn Barnich, Christiane SchomblondAbstract:The so-called covariant Poincare lemma on the induced cohomology of the space–time exterior derivative in the cohomology of the gauge part of the BRST differential is extended to cover the case of arbitrary, nonreductive Lie algebras. As a consequence, the general solution of the Wess–Zumino Consistency Condition with a nontrivial descent can, for arbitrary (super) Lie algebras, be computed in the small algebra of the one-form potentials, the ghosts and their exterior derivatives. For particular Lie algebras that are the semidirect sum of a semisimple Lie subalgebra with an ideal, a theorem by Hochschild and Serre is used to characterize more precisely the cohomology of the gauge part of the BRST differential in the small algebra. In the case of an Abelian ideal, this leads to a complete solution of the Wess–Zumino Consistency Condition in this space. As an application, the consistent deformations of 2+1 dimensional Chern–Simons theory based on iso(2,1) are rediscussed.
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Refining the anomaly Consistency Condition
Physical Review D, 2000Co-Authors: Glenn BarnichAbstract:In the extended antifield formalism, a quantum BRST differential for anomalous gauge theories is constructed. Local BRST cohomological classes are characterized, in addition to the form degree and the ghost number, by the length of their descents and of their lifts, and this both in the standard and the extended antifield formalism. It is shown that during the BRST invariant renormalization of a local BRST cohomological class, the anomaly that can appear is constrained to be a local BRST cohomological class with a shorter descent and a longer lift than the given class. As an application of both results, a simple approach to the Adler-Bardeen theorem for the non-Abelian gauge anomaly is proposed. It applies independently of the gauge fixing, of power counting restrictions, and does not rely on the use of the Callan-Symanzik equation.
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General solution of the Wess-Zumino Consistency Condition for Einstein gravity.
Physical Review D, 1995Co-Authors: Glenn Barnich, Friedemann Brandt, Marc HenneauxAbstract:The Wess-Zumino Consistency Condition for four-dimensional Einstein gravity is investigated in the space of local forms involving the fields, the ghosts, the antifields, and their derivatives. Its general solution is constructed for all values of the form degree and of the ghost number. It is shown in particular that the antifields (=sources for the BRST variations) can occur only through cohomologically trivial terms.
Marc Henneaux - One of the best experts on this subject based on the ideXlab platform.
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The Wess-Zumino Consistency Condition For p-Form Gauge Theories
Nuclear Physics B, 1999Co-Authors: Marc Henneaux, Bernard KnaepenAbstract:The general solution of the antifield-independent Wess-Zumino Consistency Condition is worked out for models involving exterior form gauge fields of arbitrary degree. We consider both the free theory and theories with Chapline-Manton couplings. Our approach relies on solving the full set of descent equations by starting from the last element down ("bottom").
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General solution of the Wess-Zumino Consistency Condition for Einstein gravity.
Physical Review D, 1995Co-Authors: Glenn Barnich, Friedemann Brandt, Marc HenneauxAbstract:The Wess-Zumino Consistency Condition for four-dimensional Einstein gravity is investigated in the space of local forms involving the fields, the ghosts, the antifields, and their derivatives. Its general solution is constructed for all values of the form degree and of the ghost number. It is shown in particular that the antifields (=sources for the BRST variations) can occur only through cohomologically trivial terms.
Nicolas Boulanger - One of the best experts on this subject based on the ideXlab platform.
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General solutions of the Wess-Zumino Consistency Condition for the Weyl anomalies
Journal of High Energy Physics, 2007Co-Authors: Nicolas BoulangerAbstract:The general solutions of the Wess-Zumino Consistency Condition for the Weyl anomalies are derived in a purely algebraic manner. The solutions are obtained, in arbitrary dimensions, by explicitly computing the cohomology of the corresponding Becchi-Rouet-Stora-Tyutin differential in the space of integrated local functions at ghost number unity.
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general solutions of the wess zumino Consistency Condition for the weyl anomalies
arXiv: High Energy Physics - Theory, 2007Co-Authors: Nicolas BoulangerAbstract:The general solutions of the Wess-Zumino Consistency Condition for the conformal (or Weyl, or trace) anomalies are derived. The solutions are obtained, in arbitrary dimensions, by explicitly computing the cohomology of the corresponding Becchi-Rouet-Stora-Tyutin differential in the space of integrated local functions at ghost number unity. This provides a purely algebraic, regularization-independent classification of the Weyl anomalies in arbitrary dimensions. The so-called type-A anomaly is shown to satisfy a non-trivial descent of equations, similarly to the non-Abelian chiral anomaly in Yang-Mills theory.
Damien Imbs - One of the best experts on this subject based on the ideXlab platform.
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SIROCCO - A versatile STM protocol with invisible read operations that satisfies the virtual world Consistency Condition
Structural Information and Communication Complexity, 2010Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to design each process the application is made up of as a sequence of transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. Of course, for efficiency, a STM system has to allow transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can easily be weakened while still providing an STM system that satisfies causal Consistency, a Condition strictly weaker than virtual world Consistency.
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a versatile stm protocol with invisible read operations that satisfies the virtual world Consistency Condition
International Conference on Structural Information and Communication Complexity, 2009Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to design each process the application is made up of as a sequence of transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. Of course, for efficiency, a STM system has to allow transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can easily be weakened while still providing an STM system that satisfies causal Consistency, a Condition strictly weaker than virtual world Consistency.
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A versatile STM protocol with invisible read operations that satisfies the virtual world Consistency Condition
2009Co-Authors: Damien Imbs, Michel RaynalAbstract:The aim of a Software Transactional Memory (STM) is to discharge the programmers from the management of synchronization in multiprocess programs that access concurrent objects. To that end, a STM system provides the programmer with the concept of a transaction. The job of the programmer is to decompose each sequential process the application is made up of into transactions. A transaction is a piece of code that accesses concurrent objects, but contains no explicit synchronization statement. It is the job of the underlying STM system to provide the illusion that each transaction appears as being executed atomically. For efficiency, a STM system allows transactions to execute concurrently. Consequently, due to the underlying STM concurrency management, a transaction commits or aborts. This paper first presents a new STM Consistency Condition, called virtual world Consistency. This Condition states that no transaction reads object values from an inconsistent global state. It is similar to opacity for the committed transactions but weaker for the aborted transactions. More precisely, it states that (1) the committed transactions can be totally ordered, and (2) the values read by each aborted transaction are consistent with respect to its causal past only. Hence, virtual world Consistency is weaker than opacity while keeping its spirit. Then, assuming the objects shared by the processes are atomic read/write objects, the paper presents a STM protocol that ensures virtual world Consistency (while guaranteeing the invisibility of the read operations). From an operational point of view, this protocol is based on a vector-clock mechanism. Finally, the paper considers the case where the shared objects are regular read/write objects. It also shows how the protocol can be weakened to satisfy the causal Consistency Condition (that is weaker than virtual world Consistency). Virtual world Consistency does not require the aborted transactions to agree on what they have seen. This is captured by the local vector clocks associated with each process and the vector timestamps associated with each object. From a comprehensive point of view, the paper addresses how the interplay of these local control informations allows the execution of a set of transactions to be provided with a global meaning.