Node Architecture

We have seen in the previous section that a massively parallel computer consists of a number of nodes connected via a communication network, and that the nodes comprise small groups of processors that share memory and other resources, although a node may also contain just a single processor. Each individual node in a parallel computer is typically essentially the same as a personal computer with the addition of specialized hardware (a host channel adaptor (HCA) or a network interface card (NIC)) to connect the computer to the network. Parallelizing an application is not strictly a matter of providing for 

An example node consisting of four quad-core AMD Opteron chips. Memory, processors, and the parallel machine interconnect are reached though a ring network formed by connecting the crossbar switches. A single quad-core AMD Opteron chip provides four cores (C0-C3), two memory controllers, the System Request Interface (SRI), the crossbar, and the LI, L2, and shared 

Each process can have multiple threads of execution. Threads provide independent execution contexts that share the same virtual memory. Nodes with multiple processors can schedule different threads and processes to execute concurrently. Sharing of data between processes is discussed in chapter 3, and an overview of programming with multiple threads is given in chapter 4. 

Another abstraction of the hardware is the virtual machine. This has been available for decades in mainframe computers but only recently appeared in mainstream processors. The virtual machine abstraction takes virtual memory and multi-tasking a step further by more completely virtualizing the processor s capabilities. Virtual machines allow multiple operating systems to run concurrently. 

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Characterization of the morphology of the lymphocytes, the reactivity of the other cells in the lymph node, and the lymph node architecture is essential in obtaining a diagnosis and predicting disease course. The nodal presentation of NHL is divided into two main categories follicular, corresponding with... 

Bartlett, E. B. (1994). Dynamic node architecture learning An information theoretic approach. NEUNET 7,129-40. 

Lymph nodes can undergo rapid and profound hyperriophy during an immune response, and FRCs are deeply involved in mah ix reorganization and the remodeling of lymph node architecture. 

Nodes often provide multiple sockets, each of which can accommodate a multicore chip (two or four sockets are common, and three-socket configurations exist as well). Figure 2.15 shows an example of a node architecture based on the quad-core AMD Opteron chip. Each chip has four cores (or processors, as we use the term here). Each core has its own first (LI) and second (L2) level caches. All four cores share the third level cache (L3). A crossbar switch connects the processors to two memory controllers for accessing off-chip memory. The crossbar has three additional high-speed links that can be used to connect other multicore chips or input/output devices. 

An in-depth, yet very approachable, discussion of network architecture is presented in Principles and Practices of Interconnection Networks by Dally and Towles. An up-to-date and informative discussion of node architecture can be... 

Unudurthi, S.D., Wolf, R.M., Hund, T.J. Role of sinoatrial node architecture in... 

Shrivastava, S. K., P. D. Ezhilchelvan, N. A. Speirs, S. Tao, and A. Tully. 1992. Principal features of the VOLTAN family of reliable node architectures for distributed systems. IEEE Transactions on Computers 41(5) 542-549. 

Transputers. At higher levels of coimectedness there is a wide variety of parallel computers. A great many parallel computers have been built using INMOS Transputer chips. Individual Transputer chips mn at 2 MELOPS or greater. Transputer chips have four communication channels, so the chips can readily be intercoimected into a two-dimensional mesh network or into any other interconnection scheme where individual nodes are four-coimected. Most Transputer systems have been built as additions to existing host computers and are SIMD type. Each Transputer has a relatively small local memory as well as access to the host s memory through the interconnection network. Not surprisingly, problems that best utilize local memory tend to achieve better performance than those that make more frequent accesses to host memory. Systems that access fast local memory and slower shared memory are often referred to as NUMA, nonuniform memory access, architecture. 

Neural net architectures come in many davors, differing in the functions used in the nodes, the number of nodes and layers, thek connectivity, and... 

Microprocessor technology permitted these technical issues to be addressed in a cost-effec tive manner. In the mid-1970s, a process control architecture referred to as a distributed control system (DCS) was introduced and almost instantly became a commercial success. A DCS consists of some number of microprocessor-based nodes that are interconnec ted by a digital communications network, often called a data highway. The key features of this architecture are as follows ... 

The process control functions and the operator interface, also referred to as man-machine interface (MMI) or human-machine interface (HMI), is provided by separate nodes. This approach is referred to as split-architecture, and it permits considerable flexibihty in choosing a configuration that most appropriately meets the needs of the application. 

The specific volumes of all the nine siloxanes were predicted as a function of temperature and the number of monofunctional units, M, and difunctional units, D. A simple 3-4-1 neural network architecture with just one hidden layer was used. The three input nodes were for the number of M groups, the number of D groups, and the temperature. The hidden layer had four neurons. The predicted variable was the specific volumes of the silox-... 

Viscosities of the siloxanes were predicted over a temperature range of 298-348 K. The semi-log plot of viscosity as a function of temperature was linear for the ring compounds. However, for the chain compounds, the viscosity increased rapidly with an increase in the chain length of the molecule. A simple 2-4-1 neural network architecture was used for the viscosity predictions. The molecular configuration was not considered here because of the direct positive effect of addition of both M and D groups on viscosity. The two input variables, therefore, were the siloxane type and the temperature level. Only one hidden layer with four nodes was used. The predicted variable was the viscosity of the siloxane. 

A very simple 2-4-1 neural network architecture with two input nodes, one hidden layer with four nodes, and one output node was used in each case. The two input variables were the number of methylene groups and the temperature. Although neural networks have the ability to learn all the differences, differentials, and other calculated inputs directly from the raw data, the training time for the network can be reduced considerably if these values are provided as inputs. The predicted variable was the density of the ester. The neural network model was trained for discrete numbers of methylene groups over the entire temperature range of 300-500 K. The... 

A 3-4-1 architecture was used in this case. The three input nodes were (1) type of weathering (moisture at... 

A method of aspirating cells from the tumor via insertion of a small-bore needle into the lesion and aspirating. Commonly used to evaluate lymph nodes or other poorly accessible sites, it has the advantage of being faster and less invasive than other biopsy methods however, it does not preserve the architecture of the tumor and may return cells that are undergoing cell death, which negates histologic analysis. 

When one, or both, the interactive modules are tridentate, bidimensional (2D) architectures can be formed. A frequently recurring pattern is the (6,3) network (honeycomb structure), which is sometimes formed when onium halides self-assemble with dihalocarbons. Halide anions work as tridentate XB acceptors and occupy the nodes while the dihalocarbons work as bidentate XB donors and form the sides that space the nodes. Such architectures are present in the co-crystals l,4-DITFB/Ph4P+Br , l,4-DITFB/Me4N+r [155], and a,oo-diiodoperfluoroalkanes/K.2.2.2.cKI [128,189]. The less planar the trigonal arrangement around the nodes, the more corrugated the honeycomb structure (Fig. 9). 

Fig. 9 Honeycomb-like architectures formed on self-assembly of halide anions (which work as tridentate XB acceptors and sit at the networks nodes) with 1,4-DITFB (which works as bidentate donor and forms network sides) (A). The angles formed by the XBs around the halide anions determine the corrugation of the honeycomb architecture, a more planar arrangement around the halide anions (as is the case of the iodide anions in adduct l,4-DITFB/Me4P+r (B) with respect to the bromide anions in adduct l,4-DITFB/Ph4P+Br (C)) results in a less corrugated honeycomb architecture...

When one, or both, of the interactive modules are tetradentate, bi- or tridimensional (3D) architectures can be formed. An example of 2D architecture is the (4,4) network present in the complex diiodoacetylene/Ph4P+ Cl (and the analogous complexes formed by bromide or iodide anions) [194] as well as in the complex l,6-diiodoperfluorohexane/tetrakis(4-pyridyl)pentaerythritol [195]. In all these complexes, the XB acceptor works as the tetradentate tecton sitting at the node of the network and the XB donor works as the linear bidentate module that spaces the nodes. 

For instance, adamantanoid architectures are formed on the self-assembly of tetradentate XB donors with tetradentate XB acceptors, both the complementary tectons alternating at the nodes of the network (this is the case in the complex CBr4/Et4N+Cl and its bromide and iodide analogues [192], in the complex tetrakis(4-pyridyl)pentaerythritol/tetrakis(4-iodiotetralluorophenyl)pentaerythritol [195], and in other systems [197]). 

Adamantanoid architectures are formed also on the self-assembly of tetradentate XB acceptors, that sit at the nodes, with bidentate XB donors, that work as nodes spacers (e.g. in the complex l,4-diiodooctafluorobutane/tetrakis(4-pyridyl)pentaerythritol [195]). 

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