Vector computer memory bank contention

A number of vector supercomputers feature very large memories. Unfortunately the large capacity memory chips that are used in these computers are much slower than the fast central processing unit (CPU) circuitry. As a result, memory bank reservation times (in CPU ticks) are much longer than on previous generations of computers. A consequence of these long reservation times is that memory bank contention is sharply increased, resulting in significantly lowered performance rates. The phenomenon of memory bank contention in vector computers is analyzed using both a Markov chain model and a Monte Carlo simulation program. The results of this analysis indicate that future generations of supercomputers must either employ much faster memory chips or else feature very large numbers of independent memory banks

Throughput analysis for a high-performance FPGA-accelerated real-time search application

We propose an FPGA design for the relevancy computation part of a high-throughput real-time search application. The application matches terms in a stream of documents against a static profile, held in off-chip memory. We present a mathematical analysis of the throughput of the application and apply it to the problem of scaling the Bloom filter used to discard nonmatches

Fast Fourier Transform algorithm design and tradeoffs

The Fast Fourier Transform (FFT) is a mainstay of certain numerical techniques for solving fluid dynamics problems. The Connection Machine CM-2 is the target for an investigation into the design of multidimensional Single Instruction Stream/Multiple Data (SIMD) parallel FFT algorithms for high performance. Critical algorithm design issues are discussed, necessary machine performance measurements are identified and made, and the performance of the developed FFT programs are measured. Fast Fourier Transform programs are compared to the currently best Cray-2 FFT program

Human Induced Pluripotent Stem Cells Derived From Adult And Fetal Hepatocytes For The Study And Treatment Of Liver Metabolic Diseases

Hepatocyte transplantation has been used to treat liver disease. The availability of cells for these procedures is quite limited. hESCs and hiPSCs may be a useful source of hepatocytes for basic research and transplantation if efficient and effective differentiation protocols were developed and problems with tumorigenicity could be overcome. Recent evidence suggests that the cell of origin may affect hiPSC differentiation. Thus, hiPSCs generated from hepatocytes may differentiate back to hepatocytes more efficiently than hiPSCs from other cell types. We examined the efficiency of reprogramming adult and fetal human hepatocytes. The present studies report the generation of 40 hiPSC lines from primary human hepatocytes under feeder-free conditions (37 from fetal hepatocytes, 2 from normal adult hepatocytes and 1 from adult hepatocytes of a patient with Crigler-Najjar Syndrome, Type-1). All lines were confirmed reprogrammed and expressed markers of pluripotency by gene expression, flow cytometry, immunofluorescence, and teratoma formation. Fetal hepatocytes were reprogrammed at a frequency over 50-fold higher than adult hepatocytes. Adult hepatocytes were only reprogrammed with 6 factors, while fetal hepatocytes could be reprogrammed with 3 or 4 factors. The increased reprogramming efficiency of fetal cells was not due to increased transduction efficiency or vector toxicity. We also report the transplantation and differentiation of human fetal hepatocyte-derived iPSCs. We show preliminary data that undifferentiated cells can engraft in mouse livers of FRG and NOD/SCID mice. Engraftment was based on human DNA presence in liver tissue. Furthermore we differentiated these cells to definitive endoderm and transplanted them to FRG mice. Human DNA and human albumin were present in mouse livers and mouse serum respectively. Finally, full hepatic differentiation was performed, although we show limited results in terms of the cells’ ability to express liver specific genes and perform liver-specific metabolism. Taken together, these studies confirm that hiPSCs can be generated from adult and fetal hepatocytes, including those with genetic diseases, and differentiated back to the hepatocyte lineage. Fetal hepatocytes reprogram much more efficiently than adult, although both could serve as useful sources of hiPSC-derived hepatocytes for basic research or transplantation if an efficient hepatic differentiation protocol could be developed

Fast Rendering of Forest Ecosystems with Dynamic Global Illumination

Real-time rendering of large-scale, forest ecosystems remains a challenging problem, in that important global illumination effects, such as leaf transparency and inter-object light scattering, are difficult to capture, given tight timing constraints and scenes that typically contain hundreds of millions of primitives. We propose a new lighting model, adapted from a model previously used to light convective clouds and other participating media, together with GPU ray tracing, in order to achieve these global illumination effects while maintaining near real-time performance. The lighting model is based on a lattice-Boltzmann method in which reflectance, transmittance, and absorption parameters are taken from measurements of real plants. The lighting model is solved as a preprocessing step, requires only seconds on a single GPU, and allows dynamic lighting changes at run-time. The ray tracing engine, which runs on one or multiple GPUs, combines multiple acceleration structures to achieve near real-time performance for large, complex scenes. Both the preprocessing step and the ray tracing engine make extensive use of NVIDIA\u27s Compute Unified Device Architecture (CUDA)