Optimizing Lossy Compression Rate-Distortion from Automatic Online Selection between SZ and ZFP

With ever-increasing volumes of scientific data produced by HPC applications, significantly reducing data size is critical because of limited capacity of storage space and potential bottlenecks on I/O or networks in writing/reading or transferring data. SZ and ZFP are the two leading lossy compressors available to compress scientific data sets. However, their performance is not consistent across different data sets and across different fields of some data sets: for some fields SZ provides better compression performance, while other fields are better compressed with ZFP. This situation raises the need for an automatic online (during compression) selection between SZ and ZFP, with a minimal overhead. In this paper, the automatic selection optimizes the rate-distortion, an important statistical quality metric based on the signal-to-noise ratio. To optimize for rate-distortion, we investigate the principles of SZ and ZFP. We then propose an efficient online, low-overhead selection algorithm that predicts the compression quality accurately for two compressors in early processing stages and selects the best-fit compressor for each data field. We implement the selection algorithm into an open-source library, and we evaluate the effectiveness of our proposed solution against plain SZ and ZFP in a parallel environment with 1,024 cores. Evaluation results on three data sets representing about 100 fields show that our selection algorithm improves the compression ratio up to 70% with the same level of data distortion because of very accurate selection (around 99%) of the best-fit compressor, with little overhead (less than 7% in the experiments).Comment: 14 pages, 9 figures, first revisio

Anxiety, Loneliness, Drug Craving, and Depression Among Substance Abusers in Sichuan Province, China

Studies have reported that anxiety had a positive effect on depression among substance abusers in males. However, little is known about the mechanism underlying this relationship in substance abusers in males. The purpose of this study was to investigate the mediating effect of loneliness and drug craving between anxiety and depression in substance abusers in males. State-Trait Anxiety Inventory, The UCLA Loneliness Scale, Drug Craving Scale, and The Center for Epidemiologic Studies Depression Scale were employed into this study to investigate 585 substance abusers in males (age range of 20-58 years: M = 33.21, SD = 6.97). Structural equation modeling and the bootstrap approach were used to analyze the mediating effect of loneliness and drug craving on the relationship between anxiety and depression. The results indicated that: Loneliness had a significant positive correlation with anxiety (r = 0.37, p < 0.001) and depression (r = 0.49, p < 0.001);Drug craving had a significant positive correlation with anxiety (r = 0.28, p < 0.001) and depression (r = 0.39, p < 0.001). Loneliness and drug craving mediated the link between anxiety and depression. There was a significant positive correlation between substance abusers in male's anxiety, loneliness, drug craving, and depression. Loneliness and drug craving had a significant mediating effect on the relationship between anxiety and depression. Therefore, it was suggested that substance abusers in male's anxiety and depression might be improved and driven by decreasing loneliness and drug craving. Targeted interventions to decrease substance abusers in male's loneliness and drug craving should be developed, implemented, and help them to recover

(Z)-1-[2-(Trifluoro­meth­yl)benzyl­idene]thio­semicarbazide

In the crystal structure of the title compound, C9H8F3N3S, all atoms except for two of the F atoms are located on a mirror plane. In the crystal, the molecules are connected by N—H⋯S hydrogen bonds, forming a mol­ecular tape along the a axis

Nearly Optimal Stochastic Approximation for Online Principal Subspace Estimation

Processing streaming data as they arrive is often necessary for high dimensional data analysis. In this paper, we analyse the convergence of a subspace online PCA iteration, as a followup of the recent work of Li, Wang, Liu, and Zhang [Math. Program., Ser. B, DOI 10.1007/s10107-017-1182-z] who considered the case for the most significant principal component only, i.e., a single vector. Under the sub-Gaussian assumption, we obtain a finite-sample error bound that closely matches the minimax information lower bound of Vu and Lei [Ann. Statist. 41:6 (2013), 2905-2947].Comment: 37 page

Parity-time electromagnetic diodes in a two-dimensional nonreciprocal photonic crystal

We propose a kind of electromagnetic (EM) diode based on a two-dimensional nonreciprocal gyrotropic photonic crystal. This periodic microstructure has separately broken symmetries in both parity (P) and time-reversal (T) but obeys parity-time (PT) symmetry. This kind of diode could support bulk one-way propagating modes either for group velocity or phase velocity with various types of negative and positive refraction. This symmetry-broken system could be a platform to realize abnormal photoelectronic devices, and it may be analogous to an electron counterpart with one-way features