990 research outputs found
Desynchronization and Wave Pattern Formation in MPI-Parallel and Hybrid Memory-Bound Programs
Analytic, first-principles performance modeling of distributed-memory
parallel codes is notoriously imprecise. Even for applications with extremely
regular and homogeneous compute-communicate phases, simply adding communication
time to computation time does often not yield a satisfactory prediction of
parallel runtime due to deviations from the expected simple lockstep pattern
caused by system noise, variations in communication time, and inherent load
imbalance. In this paper, we highlight the specific cases of provoked and
spontaneous desynchronization of memory-bound, bulk-synchronous pure MPI and
hybrid MPI+OpenMP programs. Using simple microbenchmarks we observe that
although desynchronization can introduce increased waiting time per process, it
does not necessarily cause lower resource utilization but can lead to an
increase in available bandwidth per core. In case of significant communication
overhead, even natural noise can shove the system into a state of automatic
overlap of communication and computation, improving the overall time to
solution. The saturation point, i.e., the number of processes per memory domain
required to achieve full memory bandwidth, is pivotal in the dynamics of this
process and the emerging stable wave pattern. We also demonstrate how hybrid
MPI-OpenMP programming can prevent desirable desynchronization by eliminating
the bandwidth bottleneck among processes. A Chebyshev filter diagonalization
application is used to demonstrate some of the observed effects in a realistic
setting.Comment: 18 pages, 8 figure
Mammalian E-type Cyclins Control Chromosome Pairing, Telomere Stability and CDK2 Localization in Male Meiosis
Loss of function of cyclin E1 or E2, important regulators of the mitotic cell cycle, yields viable mice, but E2-deficient males display reduced fertility. To elucidate the role of E-type cyclins during spermatogenesis, we characterized their expression patterns and produced additional deletions of Ccne1 and Ccne2 alleles in the germline, revealing unexpected meiotic functions. While Ccne2 mRNA and protein are abundantly expressed in spermatocytes, Ccne1 mRNA is present but its protein is detected only at low levels. However, abundant levels of cyclin E1 protein are detected in spermatocytes deficient in cyclin E2 protein. Additional depletion of E-type cyclins in the germline resulted in increasingly enhanced spermatogenic abnormalities and corresponding decreased fertility and loss of germ cells by apoptosis. Profound meiotic defects were observed in spermatocytes, including abnormal pairing and synapsis of homologous chromosomes, heterologous chromosome associations, unrepaired double-strand DNA breaks, disruptions in telomeric structure and defects in cyclin-dependent-kinase 2 localization. These results highlight a new role for E-type cyclins as important regulators of male meiosis
The use of happiness research for public policy
Research on happiness tends to follow a "benevolent dictator" approach where politicians pursue people's happiness. This paper takes an antithetic approach based on the insights of public choice theory. First, we inquire how the results of happiness research may be used to improve the choice of institutions. Second, we show that the policy approach matters for the choice of research questions and the kind of knowledge happiness research aims to provide. Third, we emphasize that there is no shortcut to an optimal policy maximizing some happiness indicator or social welfare function since governments have an incentive to manipulate this indicator
Faithful SGCE imprinting in iPSC-derived cortical neurons: an endogenous cellular model of myoclonus-dystonia
In neuropathology research, induced pluripotent stem cell (iPSC)-derived neurons are considered a tool closely resembling the patient brain. Albeit in respect to epigenetics, this concept has been challenged. We generated iPSC-derived cortical neurons from myoclonus-dystonia patients with mutations (W100G and R102X) in the maternally imprinted ε-sarcoglycan (SGCE) gene and analysed properties such as imprinting, mRNA and protein expression. Comparison of the promoter during reprogramming and differentiation showed tissue-independent differential methylation. DNA sequencing with methylation-specific primers and cDNA analysis in patient neurons indicated selective expression of the mutated paternal SGCE allele. While fibroblasts only expressed the ubiquitous mRNA isoform, brain-specific SGCE mRNA and ε-sarcoglycan protein were detected in iPSC-derived control neurons. However, neuronal protein levels were reduced in both mutants. Our phenotypic characterization highlights the suitability of iPSC-derived cortical neurons with SGCE mutations for myoclonus-dystonia research and, in more general terms, prompts the use of iPSC-derived cellular models to study epigenetic mechanisms impacting on health and disease
Multiple agency perspective, family control, and private information abuse in an emerging economy
Using a comprehensive sample of listed companies in Hong Kong this paper investigates how family control affects private information abuses and firm performance in emerging economies. We combine research on stock market microstructure with more recent studies of multiple agency perspectives and argue that family ownership and control over the board increases the risk of private information abuse. This, in turn, has a negative impact on stock market performance. Family control is associated with an incentive to distort information disclosure to minority shareholders and obtain private benefits of control. However, the multiple agency roles of controlling families may have different governance properties in terms of investors’ perceptions of private information abuse. These findings contribute to our understanding of the conflicting evidence on the governance role of family control within a multiple agency perspectiv
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