| 1. |
- Djurfeldt, Mikael, 1967-, et al.
(författare)
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Brain-scale simulation of the neocortex on the IBM Blue Gene/L supercomputer
- 2008
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Ingår i: IBM Journal of Research and Development. - : IBM. - 0018-8646 .- 2151-8556. ; 52:1-2, s. 31-41
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Tidskriftsartikel (refereegranskat)abstract
- Biologically detailed large-scale models of the brain can now be simulated thanks to increasingly powerful massively parallel supercomputers. We present an overview, for the general technical reader, of a neuronal network model of layers II/III of the neocortex built with biophysical model neurons. These simulations, carried out on an IBM Blue Gene/Le supercomputer, comprise up to 22 million neurons and 11 billion synapses, which makes them the largest simulations of this type ever performed. Such model sizes correspond to the cortex of a small mammal. The SPLIT library, used for these simulations, runs on single-processor as well as massively parallel machines. Performance measurements show good scaling behavior on the Blue Gene/L supercomputer up to 8,192 processors. Several key phenomena seen in the living brain appear as emergent phenomena in the simulations. We discuss the role of this kind of model in neuroscience and note that full-scale models may be necessary to preserve natural dynamics. We also discuss the need for software tools for the specification of models as well as for analysis and visualization of output data. Combining models that range from abstract connectionist type to biophysically detailed will help us unravel the basic principles underlying neocortical function.
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| 2. |
- Elmroth, Erik, et al.
(författare)
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Applying recursion to serial and parallel QR factorization leads to better performance
- 2000
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Ingår i: IBM Journal of Research and Development. - : IEEE Press. - 0018-8646 .- 2151-8556. ; 44:4, s. 605-624
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Tidskriftsartikel (refereegranskat)abstract
- We present new recursive serial and parallel algorithms for QR factorization of an m by n matrix. They improve performance. The recursion leads to an automatic variable blocking, and it also replaces a Level 2 part in a standard block algorithm with Level 3 operations. However, there are significant additional costs for creating and performing the updates, which prohibit the efficient use of the recursion for large n. We present a quantitative analysis of these extra costs. This analysis leads us to introduce a hybrid recursive algorithm that outperforms the LAPACK algorithm DGEQRF by about 20% for large square matrices and up to almost a factor of 3 for tall thin matrices. Uniprocessor performance results are presented for two IBM RS/6000(R) SP nodes-a 120-MHz IBM POWER2 node and one processor of a four-way 332-MHz IBM PowerPC(R) 604e SMP node. The hybrid recursive algorithm reaches more than 90% of the theoretical peak performance of the POWER2 node, Compared to standard block algorithms, the recursive approach also shows a significant advantage in the automatic tuning obtained from its automatic variable blocking. A successful parallel implementation on a four-way 332-MHz IBM PPC604e SMP node based on dynamic load balancing is presented. For two, three, and four processors it shows speedups of up to 1.97, 2.99, and 3.97.
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| 3. |
- Ho, Ching-Tien, et al.
(författare)
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Embedding Hyper–pyramids in Hypercubes
- 1994
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Ingår i: IBM Journal of Research and Development. - : IBM. - 0018-8646 .- 2151-8556. ; 38:1, s. 31-45
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Martorell, X, et al.
(författare)
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Blue Gene/L performance tools
- 2005
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Ingår i: IBM Journal of Research and Development. - : IBM. - 0018-8646 .- 2151-8556. ; 49:2-3, s. 407-424
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Tidskriftsartikel (refereegranskat)abstract
- Good performance monitoring is the basis of modern performance aualysis tools for application optimization. We are providing a variety of such performance analysis tools for the new Blue Gene(®)/L supercomputer. Those tools can be divided into two categories: single-node performance tools and multinode performance tools. Front a single-node perspectire, we provide standard interfaces and libraries, such as PAPI and libHPM, that propide access to the hardware performance counters for applications running on the Blue Gene/L compute nodes. From a multinode perspective, we focus on tools that analyze Message Passing Interface (MPI) behavior. Those tools work by first collecting message-passing trace data when a program runs. The trace data is then used by, graphical interface tools that analyze the behavior of applications. Using the current prototype tools, we demonstrate their usefulness and applicability with case studies of application optimization.
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| 5. |
- Rochwerger, Benny, et al.
(författare)
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The reservoir model and architecture for open federated cloud computing
- 2009
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Ingår i: IBM Journal of Research and Development. - 0018-8646 .- 2151-8556. ; 53:4
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Tidskriftsartikel (refereegranskat)abstract
- The emerging cloud-computing paradigm is rapidly gaining momentum as an alternative to traditional IT (information technology). However, contemporary cloud-computing offerings are primarily targeted for Web 2.0-style applications. Only recently have they begun to address the requirements of enterprise solutions, such as support for infrastructure service-level agreements. To address the challenges and deficiencies in the current state of the art, we propose a modular, extensible cloud architecture with intrinsic support for business service management and the federation of clouds. The goal is to facilitate an open, service-based online economy in which resources and services are transparently provisioned and managed across clouds on an on-demand basis at competitive costs with high-quality service. The Reservoir project is motivated by the vision of implementing an architecture that would enable providers of cloud infrastructure to dynamically partner with each other to create a seemingly infinite pool of IT resources while fully preserving their individual autonomy in making technological and business management decisions. To this end, Reservoir could leverage and extend the advantages of virtualization and embed autonomous management in the infrastructure. At the same time, the Reservoir approach aims to achieve a very ambitious goal: creating a foundation for next-generation enterprise-grade cloud computing.
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| 6. |
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| 7. |
- Zakharov, Alexei, et al.
(författare)
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Nano-scale 3D (E,kx,ky) band structure imaging on graphene and intercalated graphene
- 2011
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Ingår i: IBM Journal of Research and Development. - : IBM Corporation. - 0018-8646 .- 2151-8556. ; 55:4, s. 6:1-6:6
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray photoemission electron microscope (X-PEEM) equipped with a hemispherical energy analyzer is capable of fast acquisition of momentum-resolved photoelectron angular distribution patterns in a complete cone. We have applied this technique to observe the 3-D $(E, k_{x}, k_{y})$ electronic band structure of zero-, one-, and two-monolayer (ML) graphene grown ex situ on 6H-SiC(0001) substrates where a carbon buffer layer (zero ML) forms underneath the graphene layer(s). We demonstrate that the interfacial buffer layer can be converted into quasi-free-standing graphene upon intercalation of Li atoms at the interface and that such a graphene is structurally and electronically decoupled from the SiC substrate. High energy and momentum resolution of the X-PEEM, along with short data acquisition times from submicrometer areas on the surface demonstrates the uniqueness and the versatility of the technique and broadens its impact and applicability within surface science and nanotechnology.
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| 8. |
- Åström, Karl Johan
(författare)
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Computer Control of a Paper Machine : An Application of Linear Stochastic Control Theory
- 1967
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Ingår i: IBM Journal of Research and Development. - : IBM. - 2151-8556 .- 0018-8646. ; 11:4, s. 389-405
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an attempt to apply linear optimal control theory to computer control of an industrial process. The applicability of the theory is discussed. Particular attention is given to the problem of obtaining a mathematical model of process dynamics and disturbances. Results of actual measurements as well as results from on-line control experience are presented.
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| 9. |
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