Training deep networks is a time-consuming process, with networks for object recognition often requiring multiple days to train. For this reason, leveraging the resources of a cluster to speed up training is an important area of work. However, widely-popular batch-processing computational frameworks like MapReduce and Spark were not designed to support the asynchronous and communication-intensive workloads of existing distributed deep learning systems. We introduce SparkNet, a framework for training deep networks in Spark. Our implementation includes a convenient interface for reading data from Spark RDDs, a Scala interface to the Caffe deep learning framework, and a lightweight multi-dimensional tensor library. Using a simple parallelization scheme for stochastic gradient descent, SparkNet scales well with the cluster size and tolerates very high-latency communication. Furthermore, it is easy to deploy and use with no parameter tuning, and it is compatible with existing Caffe models. We quantify the dependence of the speedup obtained by SparkNet on the number of machines, the communication frequency, and the cluster's communication overhead, and we benchmark our system's performance on the ImageNet dataset.
Despite prior research on outlier mitigation, our analysis of jobs from the Facebook cluster shows that outliers still occur, especially in small jobs. Small jobs are particularly sensitive to long-running outlier tasks because of their interactive nature. Outlier mitigation strategies rely on comparing different tasks of the same job and launching speculative copies for the slower tasks. However, small jobs execute all their tasks simultaneously, thereby not providing sufficient time to observe and compare tasks. Building on the observation that clusters are underutilized, we take speculation to its logical extreme--run full clones of jobs to mitigate the effect of outliers. The heavy-tail distribution of job sizes implies that we can impact most jobs without using much resources. Trace-driven simulations show that average completion time of all the small jobs improves by 47% using cloning, at the cost of just 3% extra resources.
The main difficulty in implementing cellular automata on the Cellular Neural Network Universal Machine (CNNUM) is the need to perform arbitrary logic functions of the input neighborhood. Since the architecture computes weighted sums of this neighborhood, by using a "B-template," it is limited to threshold logic, i.e., a logical operation to be computed by a single transient must be in the class of linearly separable Boolean functions. It was shown previously how a general logic function can be implemented on the CNNUM by cascading component functions from this class-namely by the direct implementation of the minterm or maxterm formulation of the desired function. However, for functions of a 3/spl times/3 input neighborhood this method may require up to 256 stages. We propose a more efficient method for implementing general logic functions on the CNNUM and other hardwares capable of performing a threshold logic function of an input neighborhood. The class of considered component functions is a superset of the minterms and maxterms but, for purposes of searchability, ease of implementation, and robustness, a subset of the general linearly separable Boolean functions. We have formulated an algorithm that will find a sequence of weight-restricted threshold logic functions (B-templates with weights from {-1, 0, +1} and a bias) that, when cascaded together using two-input logical operations, will result in the desired Boolean function. Two examples are given to exhibit the algorithm.
Alles dreht sich um Kupfer: Die kupferkatalysierte α-Arylierung von Carbonylverbindungen verläuft über eine oxidative Addition von Iodarenen an die C-gebundene CuI-Enolatspezies 1 unter Bildung einer Aryl/CuIII-Zwischenstufe. Computerstudien bieten Einblick in den Ursprung der relativen Reaktivitäten verschiedener CuI-Enolatkomplexe in den Reaktionen mit Iodarenen.
The strength and toughness of ceramic-metal joints is often controlled by the propagation path selected by stress-induced cracks. Against a background of recent linear elastic mechanics studies, experimental results from fracture tests on ceramic/metal/ceramic sandwich geometries are described which determine both the selection of crack path and the corresponding crack extension rates. It is found that crack path selection is controlled by the path of low microstructural resistance and the driving force directionality, which itself is a function of the far-field loading and the elastic compliance mismatch across the ceramic-metal interface. However, there are instances where the compliance mismatch takes the crack off the weak microstructural path, or where cracking occurs at, or near, both interfaces (crack jumping). Such cracking configurations can be tortuous and high toughness joints result. This paper discusses the potential for predicting and engineering, interfaces with enhanced toughness.
Abstract The site‐selective palladium‐catalyzed three‐component coupling of deactivated alkenes, arylboronic acids, and N ‐fluorobenzenesulfonimide is disclosed herein. The developed methodology establishes a general, modular, and step‐economical approach to the stereoselective β‐fluorination of α,β‐unsaturated systems.
This important article demonstrates that (hetero)aryl tosylates can be efficiently converted in Pd-catalyzed amination reactions. Tosylates can be easily accessed from the corresponding phenols and are unlike triflates less expensive to prepare and give stable, crystalline solids. The reaction tolerates sensitive functionalities and proceeds even with electron-rich and sterically hindered substrates.
There have been various proposals for the pattern of F-plasmid replication during the division cycle. Here we show that the recent studies of Gordon et al. (Cell 90, 1113-1121, 1997) on the duplication and segregation of green fluorescent protein (GFP) labeled replication origins of the Escherichia coli chromosome and the F plasmid during the division cycle support the proposal that the F plasmid replicates with a cell-cycle-specific (artiocyclic) pattern.
