19,676 research outputs found
When Two Choices Are not Enough: Balancing at Scale in Distributed Stream Processing
Carefully balancing load in distributed stream processing systems has a
fundamental impact on execution latency and throughput. Load balancing is
challenging because real-world workloads are skewed: some tuples in the stream
are associated to keys which are significantly more frequent than others. Skew
is remarkably more problematic in large deployments: more workers implies fewer
keys per worker, so it becomes harder to "average out" the cost of hot keys
with cold keys.
We propose a novel load balancing technique that uses a heaving hitter
algorithm to efficiently identify the hottest keys in the stream. These hot
keys are assigned to choices to ensure a balanced load, where is
tuned automatically to minimize the memory and computation cost of operator
replication. The technique works online and does not require the use of routing
tables. Our extensive evaluation shows that our technique can balance
real-world workloads on large deployments, and improve throughput and latency
by and respectively over the previous
state-of-the-art when deployed on Apache Storm.Comment: 12 pages, 14 Figures, this paper is accepted and will be published at
ICDE 201
The universality of iterated hashing over variable-length strings
Iterated hash functions process strings recursively, one character at a time.
At each iteration, they compute a new hash value from the preceding hash value
and the next character. We prove that iterated hashing can be pairwise
independent, but never 3-wise independent. We show that it can be almost
universal over strings much longer than the number of hash values; we bound the
maximal string length given the collision probability
Applications of Fog Computing in Video Streaming
The purpose of this paper is to show the viability of fog computing in the area of video streaming in vehicles. With the rise of autonomous vehicles, there needs to be a viable entertainment option for users. The cloud fails to address these options due to latency problems experienced during high internet traffic. To improve video streaming speeds, fog computing seems to be the best option. Fog computing brings the cloud closer to the user through the use of intermediary devices known as fog nodes. It does not attempt to replace the cloud but improve the cloud by allowing faster upload and download of information. This paper explores two algorithms that would work well with vehicles and video streaming. This is simulated using a Java application, and then graphically represented. The results showed that the simulation was an accurate model and that the best algorithm for request history maintenance was the variable model
Learning-Augmented B-Trees
We study learning-augmented binary search trees (BSTs) and B-Trees via Treaps
with composite priorities. The result is a simple search tree where the depth
of each item is determined by its predicted weight . To achieve the
result, each item has its composite priority
where is the uniform
random variable. This generalizes the recent learning-augmented BSTs
[Lin-Luo-Woodruff ICML`22], which only work for Zipfian distributions, to
arbitrary inputs and predictions. It also gives the first B-Tree data structure
that can provably take advantage of localities in the access sequence via
online self-reorganization. The data structure is robust to prediction errors
and handles insertions, deletions, as well as prediction updates.Comment: 25 page
On the optimality of individual entangling-probe attacks against BB84 quantum key distribution
It is shown that an existing method to study ideal individual attacks on the
BB84 QKD protocol using error discard can be adapted to reconciliation with
error correction, and that an optimal attack can be explicitly found. Moreover,
this attack fills Luetkenhaus bound, independently of whether error positions
are leaked to Eve, proving that it is tight. In addition, we clarify why the
existence of such optimal attacks is not in contradiction with the established
``old-style'' theory of BB84 individual attacks, as incorrectly suggested
recently in a news feature.Comment: 12 pages, 3 figure
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