114 research outputs found
Network Sampling: From Static to Streaming Graphs
Network sampling is integral to the analysis of social, information, and
biological networks. Since many real-world networks are massive in size,
continuously evolving, and/or distributed in nature, the network structure is
often sampled in order to facilitate study. For these reasons, a more thorough
and complete understanding of network sampling is critical to support the field
of network science. In this paper, we outline a framework for the general
problem of network sampling, by highlighting the different objectives,
population and units of interest, and classes of network sampling methods. In
addition, we propose a spectrum of computational models for network sampling
methods, ranging from the traditionally studied model based on the assumption
of a static domain to a more challenging model that is appropriate for
streaming domains. We design a family of sampling methods based on the concept
of graph induction that generalize across the full spectrum of computational
models (from static to streaming) while efficiently preserving many of the
topological properties of the input graphs. Furthermore, we demonstrate how
traditional static sampling algorithms can be modified for graph streams for
each of the three main classes of sampling methods: node, edge, and
topology-based sampling. Our experimental results indicate that our proposed
family of sampling methods more accurately preserves the underlying properties
of the graph for both static and streaming graphs. Finally, we study the impact
of network sampling algorithms on the parameter estimation and performance
evaluation of relational classification algorithms
Graph Sample and Hold: A Framework for Big-Graph Analytics
Sampling is a standard approach in big-graph analytics; the goal is to
efficiently estimate the graph properties by consulting a sample of the whole
population. A perfect sample is assumed to mirror every property of the whole
population. Unfortunately, such a perfect sample is hard to collect in complex
populations such as graphs (e.g. web graphs, social networks etc), where an
underlying network connects the units of the population. Therefore, a good
sample will be representative in the sense that graph properties of interest
can be estimated with a known degree of accuracy. While previous work focused
particularly on sampling schemes used to estimate certain graph properties
(e.g. triangle count), much less is known for the case when we need to estimate
various graph properties with the same sampling scheme. In this paper, we
propose a generic stream sampling framework for big-graph analytics, called
Graph Sample and Hold (gSH). To begin, the proposed framework samples from
massive graphs sequentially in a single pass, one edge at a time, while
maintaining a small state. We then show how to produce unbiased estimators for
various graph properties from the sample. Given that the graph analysis
algorithms will run on a sample instead of the whole population, the runtime
complexity of these algorithm is kept under control. Moreover, given that the
estimators of graph properties are unbiased, the approximation error is kept
under control. Finally, we show the performance of the proposed framework (gSH)
on various types of graphs, such as social graphs, among others
On the Efficacy of Fine-Grained Traffic Splitting Protocols in Data Center Networks
Multi-rooted tree topologies are commonly used to construct high-bandwidth data center network fabrics. In these networks, switches typically rely on equal-cost multipath (ECMP) routing techniques to split traffic across multiple paths, such that packets within a flow traverse the same end-to-end path. Unfortunately, since ECMP splits traffic based on flow-granularity, it can cause load imbalance across paths resulting in poor utilization of network resources. More finegrained traffic splitting techniques are typically not preferred because they can cause packet reordering that can, according to conventional wisdom, lead to severe TCP throughput degradation. In this work, we revisit this fact in the context of regular data center topologies such as fat-tree architectures. We argue that packet-level traffic splitting, where packets of a flow are sprayed through all available paths, would lead to a better load-balanced network, which in turn leads to significantly more balanced queues and much higher throughput compared to ECMP
Causal-DFQ: Causality Guided Data-free Network Quantization
Model quantization, which aims to compress deep neural networks and
accelerate inference speed, has greatly facilitated the development of
cumbersome models on mobile and edge devices. There is a common assumption in
quantization methods from prior works that training data is available. In
practice, however, this assumption cannot always be fulfilled due to reasons of
privacy and security, rendering these methods inapplicable in real-life
situations. Thus, data-free network quantization has recently received
significant attention in neural network compression. Causal reasoning provides
an intuitive way to model causal relationships to eliminate data-driven
correlations, making causality an essential component of analyzing data-free
problems. However, causal formulations of data-free quantization are inadequate
in the literature. To bridge this gap, we construct a causal graph to model the
data generation and discrepancy reduction between the pre-trained and quantized
models. Inspired by the causal understanding, we propose the Causality-guided
Data-free Network Quantization method, Causal-DFQ, to eliminate the reliance on
data via approaching an equilibrium of causality-driven intervened
distributions. Specifically, we design a content-style-decoupled generator,
synthesizing images conditioned on the relevant and irrelevant factors; then we
propose a discrepancy reduction loss to align the intervened distributions of
the pre-trained and quantized models. It is worth noting that our work is the
first attempt towards introducing causality to data-free quantization problem.
Extensive experiments demonstrate the efficacy of Causal-DFQ. The code is
available at https://github.com/42Shawn/Causal-DFQ.Comment: Accepted to ICCV202
Resource Allocation for Rate and Fidelity Maximization in Quantum Networks
Existing classical optical network infrastructure cannot be immediately used
for quantum network applications due to photon loss. The first step towards
enabling quantum networks is the integration of quantum repeaters into optical
networks. However, the expenses and intrinsic noise inherent in quantum
hardware underscore the need for an efficient deployment strategy that
optimizes the allocation of quantum repeaters and memories. In this paper, we
present a comprehensive framework for network planning, aiming to efficiently
distributing quantum repeaters across existing infrastructure, with the
objective of maximizing quantum network utility within an entanglement
distribution network. We apply our framework to several cases including a
preliminary illustration of a dumbbell network topology and real-world cases of
the SURFnet and ESnet. We explore the effect of quantum memory multiplexing
within quantum repeaters, as well as the influence of memory coherence time on
quantum network utility. We further examine the effects of different fairness
assumptions on network planning, uncovering their impacts on real-time network
performance.Comment: 18 pages, 8 figures, 3 appendice
vHaul: Towards Optimal Scheduling of Live Multi-VM Migration for Multi-tier Applications
Abstract—Live virtual machine (VM) migration enables seamless movement of an online server from one location to another to achieve failure recovery, load balancing, and system maintenance. Beyond single VM migration, a multi-tier application involves a group of correlated VMs and its live mi-gration will require careful scheduling of the migrations of the member VMs. Our observations from extensive experiments using a variety of multi-tier applications suggest that, in a dedicated data center with dedicated migration links, different migration strategies result in distinct performance impacts on a multi-tier application. The root cause of the problem is the inter-dependence between functional components of a multi-tier application. We leverage these observations in vHaul, a system that coordinates multi-VM migration to approximate the optimal scheduling. Our evaluation of a vHaul prototype on Xen suggests that vHaul yields the optimal multi-VM live migra-tion schedules. Further, our application-level evaluation using Apache Olio, a web 2.0 cloud application, shows that the optimal migration schedule produced by vHaul outperforms the worst-case schedule by 43 % in application throughput. Moreover, the optimal schedule significantly reduces service latency during migration by up to 70%
Fast and Resource-Efficient Object Tracking on Edge Devices: A Measurement Study
Object tracking is an important functionality of edge video analytic systems
and services. Multi-object tracking (MOT) detects the moving objects and tracks
their locations frame by frame as real scenes are being captured into a video.
However, it is well known that real time object tracking on the edge poses
critical technical challenges, especially with edge devices of heterogeneous
computing resources. This paper examines the performance issues and
edge-specific optimization opportunities for object tracking. We will show that
even the well trained and optimized MOT model may still suffer from random
frame dropping problems when edge devices have insufficient computation
resources. We present several edge specific performance optimization
strategies, collectively coined as EMO, to speed up the real time object
tracking, ranging from window-based optimization to similarity based
optimization. Extensive experiments on popular MOT benchmarks demonstrate that
our EMO approach is competitive with respect to the representative methods for
on-device object tracking techniques in terms of run-time performance and
tracking accuracy. EMO is released on Github at
https://github.com/git-disl/EMO
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