A fast asynchronous GVT algorithm for shared memory multiprocessor architectures

Xiao, Zhonge; Gomes, Fabian; Unger, Brian; Cleary, John G.

doi:10.1109/pads.1995.404296

Cited by 9 publications

(8 citation statements)

References 9 publications

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“…Similar considerations apply to the work in [15], which presents a GVT algorithm for observable shared memory Time Warp systems (although observability was formally defined later in literature by [1]). In particular, this work is based on a critical section that is used to atomically update the entries of an array of elements, with size equal to the number of participating processes/threads.…”

Section: Related Workmentioning

confidence: 90%

Wait-Free Global Virtual Time Computation in Shared Memory TimeWarp Systems

Pellegrini

Quaglia

2014

2014 IEEE 26th International Symposium on Computer Architecture and High Performance Computing

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Global Virtual Time (GVT) is a powerful abstraction used to discriminate what events belong (and what do not belong) to the past history of a parallel/distributed computation. For high performance simulation systems based on the Time Warp synchronization protocol, where concurrent simulation objects are allowed to process their events speculatively and causal consistency is achieved via rollback/recovery techniques, GVT is used to determine which portion of the simulation can be considered as committed. Hence it is the base for actuating memory recovery (e.g. of obsolete logs that were taken in order to support state recoverability) and nonrevocable operations (e.g. I/O). For shared memory implementations of simulation platforms based on the Time Warp protocol, the reference GVT algorithm is the one presented by Fujimoto and Hybinette [1]. However, this algorithm relies on critical sections that make it non-wait-free, and which can hamper scalability. In this article we present a waitfree shared memory GVT algorithm that requires no critical section. Rather, correct coordination across the processes while computing the GVT value is achieved via memory atomic operations, namely compare-and-swap. The price paid by our proposal is an increase in the number of GVT computation phases, as opposed to the single phase required by the proposal in [1]. However, as we show via the results of an experimental study, the wait-free nature of the phases carried out in our GVT algorithm pays-off in reducing the actual cost incurred by the proposal in [1].

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Section: Related Workmentioning

confidence: 90%

Wait-Free Global Virtual Time Computation in Shared Memory TimeWarp Systems

Pellegrini

Quaglia

2014

2014 IEEE 26th International Symposium on Computer Architecture and High Performance Computing

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“…This problem can be solved by using an interrupt mechanism to compute the local minimum in each processor. Independently, Xiao et al [1995] report a shared-memory algorithm for computing GVT where a processor interrogates shared variables maintained by each processor, enabling any processor to compute GVT without waiting for another processor to respond. This entails somewhat higher overheads than the algorithm described here, however [Xiao et al 1995].…”

Section: Methodsmentioning

confidence: 99%

Computing global virtual time in shared-memory multiprocessors

Fujimoto

Hybinette

1997

ACM Trans. Model. Comput. Simul.

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Global virtual time (GVT) is used in the Time Warp synchronization mechanism to perform irrevocable operations such as I/O and to reclaim storage. Most existing algorithms for computing GVT assume a message-passing programming model. Here, GVT computation is examined in the context of a shared-memory model. We observe that computation of GVT is much simpler in shared-memory multiprocessors because these machines normally guarantee that no two processors will observe a set of memory operations as occurring in different orders. Exploiting this fact, we propose an efficient, asynchronous, shared-memory GVT algorithm and prove its correctness. This algorithm does not require message acknowledgments, special GVT messages, or FIFO delivery of messages, and requires only a minimal number of shared variables and data structures. The algorithm only requires one round of interprocessor communication to compute GVT, in contrast to many message-based algorithms that require two. An efficient implementation is described that eliminates the need for a processor to explicitly compute a local minimum for time warp systems using a lowest-timestamp-first scheduling policy in each processor.In addition, we propose a new mechanism called on-the-fly fossil collection that enables efficient storage reclamation for simulations containing large numbers, e.g., hundreds of thousand or even millions of simulator objects. On-the-fly fossil collection can be used in time warp systems executing on either shared-memory or message-based machines. Performance measurements of the GVT algorithm and the on-the-fly fossil collection mechanism on a Kendall Square Research KSR-2 machine demonstrate that these techniques enable frequent GVT and fossil collections, e.g., every millisecond, without incurring a significant performance penalty.

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“…In shared memory algorithms, the shared variable approach is a general method for calculating the GVT value. For example, fast asynchronous GVT algorithm (FA-GVT) proposed by Xiao et al [19] is a typical GVT algorithm for shared memory machines. The FA-GVT algorithm triggers GVT computation according to wall-clock time intervals and relies on shared variables that are accessed by worker-threads to compute the GVT value under the control of a critical section.…”

Section: Shared Memory Algorithmsmentioning

confidence: 99%

“…Shared memory algorithm assumes that certain variables are accessible by all processors. So they perform well on symmetric multiprocessing machines [15,18,19]. Distributed memory algorithm does not use global variables and therefore is more scalable.…”

Section: Introductionmentioning

confidence: 99%

A Scalable GVT Estimation Algorithm for PDES: Using Lower Bound of Event-Bulk-Time

Peng

Qin²,

Yin³

2015

Mathematical Problems in Engineering

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Global Virtual Time computation of Parallel Discrete Event Simulation is crucial for conducting fossil collection and detecting the termination of simulation. The triggering condition of GVT computation in typical approaches is generally based on the wall-clock time or logical time intervals. However, the GVT value depends on the timestamps of events rather than the wall-clock time or logical time intervals. Therefore, it is difficult for the existing approaches to select appropriate time intervals to compute the GVT value. In this study, we propose a scalable GVT estimation algorithm based on Lower Bound of Event-Bulk-Time, which triggers the computation of the GVT value according to the number of processed events. In order to calculate the number of transient messages, our algorithm employs Event-Bulk to record the messages sent and received by Logical Processes. To eliminate the performance bottleneck, we adopt an overlapping computation approach to distribute the workload of GVT computation to all worker-threads. We compare our algorithm with the fast asynchronous GVT algorithm using PHOLD benchmark on the shared memory machine. Experimental results indicate that our algorithm has a light overhead and shows higher speedup and accuracy of GVT computation than the fast asynchronous GVT algorithm.

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A fast asynchronous GVT algorithm for shared memory multiprocessor architectures

Cited by 9 publications

References 9 publications

Wait-Free Global Virtual Time Computation in Shared Memory TimeWarp Systems

Wait-Free Global Virtual Time Computation in Shared Memory TimeWarp Systems

Computing global virtual time in shared-memory multiprocessors

A Scalable GVT Estimation Algorithm for PDES: Using Lower Bound of Event-Bulk-Time

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