The Experts below are selected from a list of 12489 Experts worldwide ranked by ideXlab platform
Chris D. A. Blair - One of the best experts on this subject based on the ideXlab platform.
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non commutativity and non Associativity of the doubled string in non geometric backgrounds
Journal of High Energy Physics, 2015Co-Authors: Chris D. A. BlairAbstract:We use a T-duality invariant action to investigate the behaviour of a string in non-geometric backgrounds, where there is a non-trivial global O(D, D) patching or monodromy. This action leads to a set of Dirac brackets describing the dynamics of the doubled string, with these brackets determined only by the monodromy. This allows for a simple derivation of non-commutativity and non-Associativity in backgrounds which are (even locally) non-geometric. We focus here on the example of the three-torus with H-flux, finding non-commutativity but not non-Associativity. We also comment on the relation to the exotic 5 2 2 brane, which shares the same monodromy.
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Non-commutativity and non-Associativity of the doubled string in non-geometric backgrounds
Journal of High Energy Physics, 2015Co-Authors: Chris D. A. BlairAbstract:We use a T-duality invariant action to investigate the behaviour of a string in non-geometric backgrounds, where there is a non-trivial global $O(D,D)$ patching or monodromy. This action leads to a set of Dirac brackets describing the dynamics of the doubled string, with these brackets determined only by the monodromy. This allows for a simple derivation of non-commutativity and non-Associativity in backgrounds which are (even locally) non-geometric. We focus here on the example of the three-torus with H-flux, finding non-commutativity but not non-Associativity, and also comment on the relation to the exotic $5^2_2$ brane, which shares the same monodromy.
Christos Kozyrakis - One of the best experts on this subject based on the ideXlab platform.
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vantage scalable and efficient fine grain cache partitioning
International Symposium on Computer Architecture, 2011Co-Authors: Daniel Sanchez, Christos KozyrakisAbstract:Cache partitioning has a wide range of uses in CMPs, from guaranteeing quality of service and controlled sharing to security-related techniques. However, existing cache partitioning schemes (such as way-partitioning) are limited to coarse-grain allocations, can only support few partitions, and reduce cache Associativity, hurting performance. Hence, these techniques can only be applied to CMPs with 2-4 cores, but fail to scale to tens of cores. We present Vantage, a novel cache partitioning technique that overcomes the limitations of existing schemes: caches can have tens of partitions with sizes specified at cache line granularity, while maintaining high Associativity and strong isolation among partitions. Vantage leverages cache arrays with good hashing and Associativity, which enable soft-pinning a large portion of cache lines. It enforces capacity allocations by controlling the replacement process. Unlike prior schemes, Vantage provides strict isolation guarantees by partitioning most (e.g. 90%) of the cache instead of all of it. Vantage is derived from analytical models, which allow us to provide strong guarantees and bounds on Associativity and sizing independent of the number of partitions and their behaviors. It is simple to implement, requiring around 1.5% state overhead and simple changes to the cache controller. We evaluate Vantage using extensive simulations. On a 32-core system, using 350 multiprogrammed workloads and one partition per core, partitioning the last-level cache with conventional techniques degrades throughput for 71% of the workloads versus an unpartitioned cache (by 7% average, 25% maximum degradation), even when using 64-way caches. In contrast, Vantage improves throughput for 98% of the workloads, by 8% on average (up to 20%), using a 4-way cache.
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the zcache decoupling ways and Associativity
International Symposium on Microarchitecture, 2010Co-Authors: Daniel Sanchez, Christos KozyrakisAbstract:The ever-increasing importance of main memory latency and bandwidth is pushing CMPs towards caches with higher capacity and Associativity. Associativity is typically improved by increasing the number of ways. This reduces conflict misses, but increases hit latency and energy, placing a stringent trade-off on cache design. We present the zcache, a cache design that allows much higher Associativity than the number of physical ways (e.g. a 64-associative cache with 4 ways). The zcache draws on previous research on skew-associative caches and cuckoo hashing. Hits, the common case, require a single lookup, incurring the latency and energy costs of a cache with a very low number of ways. On a miss, additional tag lookups happen off the critical path, yielding an arbitrarily large number of replacement candidates for the incoming block. Unlike conventional designs, the zcache provides Associativity by increasing the number of replacement candidates, but not the number of cache ways. To understand the implications of this approach, we develop a general analysis framework that allows to compare Associativity across different cache designs (e.g. a set-associative cache and a zcache) by representing Associativity as a probability distribution. We use this framework to show that for zcaches, Associativity depends only on the number of replacement candidates, and is independent of other factors (such as the number of cache ways or the workload). We also show that, for the same number of replacement candidates, the Associativity of a zcache is superior than that of a set-associative cache for most workloads. Finally, we perform detailed simulations of multithreaded and multiprogrammed workloads on a large-scale CMP with zcache as the last-level cache. We show that zcaches provide higher performance and better energy efficiency than conventional caches without incurring the overheads of designs with a large number of ways.
Daniel Sanchez - One of the best experts on this subject based on the ideXlab platform.
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vantage scalable and efficient fine grain cache partitioning
International Symposium on Computer Architecture, 2011Co-Authors: Daniel Sanchez, Christos KozyrakisAbstract:Cache partitioning has a wide range of uses in CMPs, from guaranteeing quality of service and controlled sharing to security-related techniques. However, existing cache partitioning schemes (such as way-partitioning) are limited to coarse-grain allocations, can only support few partitions, and reduce cache Associativity, hurting performance. Hence, these techniques can only be applied to CMPs with 2-4 cores, but fail to scale to tens of cores. We present Vantage, a novel cache partitioning technique that overcomes the limitations of existing schemes: caches can have tens of partitions with sizes specified at cache line granularity, while maintaining high Associativity and strong isolation among partitions. Vantage leverages cache arrays with good hashing and Associativity, which enable soft-pinning a large portion of cache lines. It enforces capacity allocations by controlling the replacement process. Unlike prior schemes, Vantage provides strict isolation guarantees by partitioning most (e.g. 90%) of the cache instead of all of it. Vantage is derived from analytical models, which allow us to provide strong guarantees and bounds on Associativity and sizing independent of the number of partitions and their behaviors. It is simple to implement, requiring around 1.5% state overhead and simple changes to the cache controller. We evaluate Vantage using extensive simulations. On a 32-core system, using 350 multiprogrammed workloads and one partition per core, partitioning the last-level cache with conventional techniques degrades throughput for 71% of the workloads versus an unpartitioned cache (by 7% average, 25% maximum degradation), even when using 64-way caches. In contrast, Vantage improves throughput for 98% of the workloads, by 8% on average (up to 20%), using a 4-way cache.
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the zcache decoupling ways and Associativity
International Symposium on Microarchitecture, 2010Co-Authors: Daniel Sanchez, Christos KozyrakisAbstract:The ever-increasing importance of main memory latency and bandwidth is pushing CMPs towards caches with higher capacity and Associativity. Associativity is typically improved by increasing the number of ways. This reduces conflict misses, but increases hit latency and energy, placing a stringent trade-off on cache design. We present the zcache, a cache design that allows much higher Associativity than the number of physical ways (e.g. a 64-associative cache with 4 ways). The zcache draws on previous research on skew-associative caches and cuckoo hashing. Hits, the common case, require a single lookup, incurring the latency and energy costs of a cache with a very low number of ways. On a miss, additional tag lookups happen off the critical path, yielding an arbitrarily large number of replacement candidates for the incoming block. Unlike conventional designs, the zcache provides Associativity by increasing the number of replacement candidates, but not the number of cache ways. To understand the implications of this approach, we develop a general analysis framework that allows to compare Associativity across different cache designs (e.g. a set-associative cache and a zcache) by representing Associativity as a probability distribution. We use this framework to show that for zcaches, Associativity depends only on the number of replacement candidates, and is independent of other factors (such as the number of cache ways or the workload). We also show that, for the same number of replacement candidates, the Associativity of a zcache is superior than that of a set-associative cache for most workloads. Finally, we perform detailed simulations of multithreaded and multiprogrammed workloads on a large-scale CMP with zcache as the last-level cache. We show that zcaches provide higher performance and better energy efficiency than conventional caches without incurring the overheads of designs with a large number of ways.
Lizhong Chen - One of the best experts on this subject based on the ideXlab platform.
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Futility Scaling: High-Associativity Cache Partitioning (Extended Version) Futility Scaling: High-Associativity Cache Partitioning (Extended Version)
2020Co-Authors: Ruisheng Wang, Lizhong Chen, Ming HsiehAbstract:Abstract-As shared last level caches are widely used in many-core CMPs to boost system performance, partitioning a large shared cache among multiple concurrently running applications becomes increasingly important in order to reduce destructive interference. However, while recent works start to show the promise of using replacement-based partitioning schemes, such existing schemes either suffer from severe Associativity degradation when the number of partitions is high, or lack the ability to precisely partition the whole cache which leads to decreased resource efficiency. In this paper, we propose Futility Scaling (FS), a novel replacement-based cache partitioning scheme that can precisely partition the whole cache while still maintain high Associativity even with a large number of partitions. The futility of a cache line represents the uselessness of the line to application performance and can be ranked in different ways by various policies, e.g., LRU and LFU. The idea of FS is to control the size of a partition by properly scaling the futility of its cache lines. We study the properties of FS on both Associativity and sizing in an analytical framework, and we present a feedback-based implementation of FS that incurs little overhead in practice. Simulation results show that FS improves performance over previously proposed Vantage and PriSM by up to 6.0% and 13.7%, respectively
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futility scaling high Associativity cache partitioning
International Symposium on Microarchitecture, 2014Co-Authors: Ruisheng Wang, Lizhong ChenAbstract:As shared last level caches are widely used in many-core CMPs to boost system performance, partitioning a large shared cache among multiple concurrently running applications becomes increasingly important in order to reduce destructive interference. However, while recent works start to show the promise of using replacement-based partitioning schemes, such existing schemes either suffer from the severe Associativity degradation when the number of partitions is high, or lack the ability to precisely partition the whole cache which leads to decreased resource efficiency. In this paper, we propose Futility Scaling (FS), a novel replacement-based cache partitioning scheme that can precisely partition the whole cache while still maintaining high Associativity even with a large number of partitions. The futility of a cache line represents the uselessness of this line to application performance and can be ranked in different ways by various policies, e.g., LRU and LFU. The idea of FS is to control the size of a partition by properly scaling the futility of its cache lines. We study the properties of FS on both Associativity and sizing in an analytical framework, and present a feedback-based implementation of FS that incurs little overhead in practice. Simulation results show that, FS improves performance over previously proposed Vantage and Prism by up to 6.0% and 13.7%, respectively.
Peter Sarkoci - One of the best experts on this subject based on the ideXlab platform.
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Associativity of triangular norms characterized by the geometry of their level sets
Fuzzy Sets and Systems, 2012Co-Authors: Milan Petrík, Peter SarkociAbstract:Associativity of triangular norms is an algebraic property which, unlike for example their commutativity, is usually understood as hardly visually interpretable. This problem has been studied intensively in the last decade and, as a result, geometric symmetries of triangular norms with involutive level sets have been revealed. The presented paper intends to introduce a different approach which gives more general results. The inspiration is taken from web geometry, a branch of differential geometry, and its concept of Reidemeister closure condition which is known to provide a geometric characterization of Associativity of loops. The paper shows that this concept can be adopted successfully for triangular norms so that it characterizes their Associativity in a similar way. Moreover, the offered adaptation preserves the beneficial transparency and simplicity of the Reidemeister closure condition. This way, a visual characterization of the Associativity, based on the geometry of the level sets, is provided for general, continuous, and continuous Archimedean triangular norms.
