404 research outputs found
Unbiased Compression Saves Communication in Distributed Optimization: When and How Much?
Communication compression is a common technique in distributed optimization
that can alleviate communication overhead by transmitting compressed gradients
and model parameters. However, compression can introduce information
distortion, which slows down convergence and incurs more communication rounds
to achieve desired solutions. Given the trade-off between lower per-round
communication costs and additional rounds of communication, it is unclear
whether communication compression reduces the total communication cost.
This paper explores the conditions under which unbiased compression, a widely
used form of compression, can reduce the total communication cost, as well as
the extent to which it can do so. To this end, we present the first theoretical
formulation for characterizing the total communication cost in distributed
optimization with communication compression. We demonstrate that unbiased
compression alone does not necessarily save the total communication cost, but
this outcome can be achieved if the compressors used by all workers are further
assumed independent. We establish lower bounds on the communication rounds
required by algorithms using independent unbiased compressors to minimize
smooth convex functions and show that these lower bounds are tight by refining
the analysis for ADIANA. Our results reveal that using independent unbiased
compression can reduce the total communication cost by a factor of up to
when all local smoothness constants are
constrained by a common upper bound, where is the number of workers and
is the condition number of the functions being minimized. These
theoretical findings are supported by experimental results.Comment: Accepted by NeurIPS 202
Modified propagation of gravitational waves from the early radiation era
We study the propagation of cosmological gravitational wave (GW) backgrounds
from the early radiation era until the present day in modified theories of
gravity. Comparing to general relativity (GR), we study the effects that
Horndeski parameters, such as the run rate of the effective Planck mass
and the tensor speed excess , have on the
present-day GW spectrum. We use both the WKB estimate, which provides an
analytical description but fails at superhorizon scales, and numerical
simulations that allow us to go beyond the WKB approximation. We show that
makes relatively insignificant changes to the GR solution,
especially taking into account the constraints on its value from GW
observations by the LIGO-Virgo collaboration, while can
introduce modifications to the spectral slopes of the GW energy spectrum in the
low-frequency regime depending on the considered time evolution of . The latter effect is additional to the damping or growth occurring equally
at all scales that can be predicted by the WKB approximation. In light of the
recent observations by pulsar timing array collaborations and future detectors
such as SKA, LISA, DECIGO, BBO, or ET, we show that, in most of the cases,
constraints can not be placed on the effects of and the
initial GW energy density separately, but only on the
combined effects of the two.Comment: 31 pages, 11 figures, 2 table
Determinants of Executive Compensation in China: The Role and Effect of Corporate Governance and Firm Performance ——Empirical Evidence from Listed Manufacturing Firms
In response to public outrage over the executive pay scandals, this paper examines the role and effect of firm performance and corporate governance (CG) on executive compensation in China based on the optimal contract theory and the managerial power theory, contributing to the empirical research on compensation in developing countries.
The sample in this research includes 1078 listed manufacturing firms whose executive compensation, performance and corporate governance data from 2015 to 2018 are collected through the CSMAR and CCER databases. On top of that, quantitative analysis is employed to analyze this panel data. By conducting two-way fixed-effect regression models, this research finds the positive connections between firm performance and executive cash compensation, among which the pay-for-market-performance sensitivity is limited and generally lower than the pay-for-operation-performance sensitivity. However, it is also found that CEOs of non-state-owned enterprises (non-SOEs) might increase their pay and decouple the positive connection between executive pay and operation performance when they concurrently serve as the chairman of the board of directors.
Moreover, little evidence is found to support the direct and moderating effect of the board independence, presence of compensation committee and the ownership concentration. It indicates that the quality and monitoring role of large shareholders and the board might be overestimated. Therefore, in the future policymaking process, it is necessary to find a way to truly enhance the monitoring role and to increase the bargaining power of large shareholders and the board regarding the design and implementation of optimal executive compensation contracts
Enhanced cancer therapy with cold-controlled drug release and photothermal warming enabled by one nanoplatform
Stimuli-responsive nanoparticles hold great promise for drug delivery to improve the safety and efficacy of cancer therapy. One of the most investigated stimuli-responsive strategies is to induce drug release by heating with laser, ultrasound, or electromagnetic field. More recently, cryosurgery (also called cryotherapy and cryoablation), destruction of diseased tissues by first cooling/freezing and then warming back, has been used to treat various diseases including cancer in the clinic. Here we developed a cold-responsive nanoparticle for controlled drug release as a result of the irreversible disassembly of the nanoparticle when cooled to below ∼10 °C. Furthermore, this nanoparticle can be used to generate localized heating under near infrared (NIR) laser irradiation, which can facilitate the warming process after cooling/freezing during cryosurgery. Indeed, the combination of this cold-responsive nanoparticle with ice cooling and NIR laser irradiation can greatly augment cancer destruction both in vitro and in vivo with no evident systemic toxicity
CSP: Self-Supervised Contrastive Spatial Pre-Training for Geospatial-Visual Representations
Geo-tagged images are publicly available in large quantities, whereas labels
such as object classes are rather scarce and expensive to collect. Meanwhile,
contrastive learning has achieved tremendous success in various natural image
and language tasks with limited labeled data. However, existing methods fail to
fully leverage geospatial information, which can be paramount to distinguishing
objects that are visually similar. To directly leverage the abundant geospatial
information associated with images in pre-training, fine-tuning, and inference
stages, we present Contrastive Spatial Pre-Training (CSP), a self-supervised
learning framework for geo-tagged images. We use a dual-encoder to separately
encode the images and their corresponding geo-locations, and use contrastive
objectives to learn effective location representations from images, which can
be transferred to downstream supervised tasks such as image classification.
Experiments show that CSP can improve model performance on both iNat2018 and
fMoW datasets. Especially, on iNat2018, CSP significantly boosts the model
performance with 10-34% relative improvement with various labeled training data
sampling ratios.Comment: In: ICML 2023, Jul 23 - 29, 2023, Honolulu, Hawaii, US
OEBench: Investigating Open Environment Challenges in Real-World Relational Data Streams
How to get insights from relational data streams in a timely manner is a hot
research topic. This type of data stream can present unique challenges, such as
distribution drifts, outliers, emerging classes, and changing features, which
have recently been described as open environment challenges for machine
learning. While existing studies have been done on incremental learning for
data streams, their evaluations are mostly conducted with manually partitioned
datasets. Thus, a natural question is how those open environment challenges
look like in real-world relational data streams and how existing incremental
learning algorithms perform on real datasets. To fill this gap, we develop an
Open Environment Benchmark named OEBench to evaluate open environment
challenges in relational data streams. Specifically, we investigate 55
real-world relational data streams and establish that open environment
scenarios are indeed widespread in real-world datasets, which presents
significant challenges for stream learning algorithms. Through benchmarks with
existing incremental learning algorithms, we find that increased data quantity
may not consistently enhance the model accuracy when applied in open
environment scenarios, where machine learning models can be significantly
compromised by missing values, distribution shifts, or anomalies in real-world
data streams. The current techniques are insufficient in effectively mitigating
these challenges posed by open environments. More researches are needed to
address real-world open environment challenges. All datasets and code are
open-sourced in https://github.com/sjtudyq/OEBench
RA-ICM: A Novel Independent Cascade Model Incorporating User Relationships and Attitudes
The rapid development of social networks has a wide range of social effects,
which facilitates the study of social issues. Accurately forecasting the
information propagation process within social networks is crucial for promptly
understanding the event direction and effectively addressing social problems in
a scientific manner. The relationships between non-adjacent users and the
attitudes of users significantly influence the information propagation process
within social networks. However, existing research has ignored these two
elements, which poses challenges for accurately predicting the information
propagation process. This limitation significantly hinders the study of
emotional contagion and influence maximization in social networks. To address
these issues, by considering the relationships between non-adjacent users and
the influence of user attitudes, we propose a new information propagation model
based on the independent cascade model. Experimental results obtained from six
real Weibo datasets validate the effectiveness of the proposed model, which is
reflected in increased prediction accuracy and reduced time complexity.
Furthermore, the information dissemination trend in social networks predicted
by the proposed model closely resembles the actual information propagation
process, which demonstrates the superiority of the proposed model
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