A Scalable Flash-Based Hardware Architecture for the Hierarchical Temporal Memory Spatial Pooler

Hierarchical temporal memory (HTM) is a biomimetic machine learning algorithm focused upon modeling the structural and algorithmic properties of the neocortex. It is comprised of two components, realizing pattern recognition of spatial and temporal data, respectively. HTM research has gained momentum in recent years, leading to both hardware and software exploration of its algorithmic formulation. Previous work on HTM has centered on addressing performance concerns; however, the memory-bound operation of HTM presents significant challenges to scalability. In this work, a scalable flash-based storage processor unit, Flash-HTM (FHTM), is presented along with a detailed analysis of its potential scalability. FHTM leverages SSD flash technology to implement the HTM cortical learning algorithm spatial pooler. The ability for FHTM to scale with increasing model complexity is addressed with respect to design footprint, memory organization, and power efficiency. Additionally, a mathematical model of the hardware is evaluated against the MNIST dataset, yielding 91.98% classification accuracy. A fully custom layout is developed to validate the design in a TSMC 180nm process. The area and power footprints of the spatial pooler are 30.538mm2 and 5.171mW, respectively. Storage processor units have the potential to be viable platforms to support implementations of HTM at scale

SoC-Based In-Storage Processing: Bringing Flexibility and Efficiency to Near-Data Processing

Data are among the most valuable assets in the modern world, and they have caused a revolutionary stage in human life. Nowadays, companies make knowledge-based decisions by analyzing a huge volume of data, super-scale data centers are used to process customers’ data to suggest products to them, government services rely on the data people provide to them, and there are many similar cases wherein data are used as an important asset. Data are originally stored in storage systems. To process data, application servers need to fetch the data from storage units, which imposes the cost of moving the data to the system. This cost has a direct relationship to the distance of the processing engines from the data, and this is the key motivation for the emergence of distributed processing platforms such as Hadoop, which bring the process closer to the data.In-storage processing (ISP) pushes the “bring the process to data” paradigm to its ultimate boundaries by utilizing processing engines inside the storage units to process data. The architecture of modern solid-state drives (SSDs) provides a suitable environment for implementing such technology. Thus, this dissertation focuses on SSD architectures that are able to run user applications in-place, which are called computational storage devices (CSDs). In this dissertation, we propose CSD architectures and investigate the benefits of deploying CSDs for running different applications. This research uses a practical approach that includes building fully functional prototypes of the proposed CSD architectures, developing storage systems equipped with the CSDs, and running different benchmarks to investigate the benefits of deploying the CSDs in the systems. This research proposes two different CSD architectures, namely CompStor and Catalina.These are the first CSDs to be equipped with a dedicated ISP engine for running user applications in-place that includes a quad-core ARM Cortex-A53 processor together with FPGA- and application-specific integrated circuit (ASIC) based accelerators. The proposed architectures run a full-fledged operating system inside, which provides a flexible environment for running a wide range of user applications in-place. The system-on-chip (SOC) based architecture of Catalina CSD, together with a software stack developed for seamless deployment of the CSD, makes it a platform for the implementation of different ISP concepts and ideas.To the best of our knowledge, Catalina is the only ISP platform that can be seamlessly deployed in clusters to run distributed applications such as Hadoop MapReduce and message passing interface (MPI) based applications in-place without any modifications to the underlying distributed processing framework. We performed extensive experimental tests using several datasets on both CompStor and Catalina CSDs. The experimental results show up to 2.2x and 4.3x improvements in performance and energy consumption, respectively, for running Hadoop MapReduce benchmarks using Catalina CSDs and up to 5.4x and 8.9x improvements for running 1-, 2-, and 3-dimensional DFT algorithms due to the Neon SIMD engines inside Catalina. Additionally, using FPGA-based accelerators, Catalina CSDs can improve the performance and energy consumption of a highly demanding image similarity search application up to 11x and 7x, respectively

A Flexible BCH decoder for Flash Memory Systems using Cascaded BCH codes

NAND ash memories are widely used in consumer electronics, such as tablets, personal computers, smartphones, and gaming systems. However, unlike other standard storage devices, these ash memories suffer from various random errors. In order to address these reliability issues, various error correction codes (ECC) are employed. Bose-Chaudhuri Hocquenghem (BCH) code is the most common ECC used to address the errors in modern ash memories. Because of the limitation of the realization of the BCH codes for more extensive error correction, the modern ash memory devices use Low-density parity-check (LDPC) codes for error correction scheme. The realization of the LDPC decoders have greater complexity than BCH decoders, so these ECC decoders are implemented within the ash memory device. This thesis analyzes the limitation imposed by the state of the art implementation of BCH decoders and proposes a cascaded BCH code to address these limitations. In order to support a variety of ash memory devices, there are three main challenges to be addressed for BCH decoders. First, the latency of the BCH decoders, in the case of no error scenario, should be less than 100us. Second, there should be flexibility in supporting different ECC block size; more precisely, the solution should be able to support 256, 512, 1024, and 2048 bytes of ECC block. Third, there should be flexibility in supporting different bit errors. A recent development with Graphical Processing Units (GPUs) has attracted many researchers to use GPUs for non-graphical implementation. These GPUs are used in many consumer electronics as part of the system on chip (SOC) configuration. In this thesis we studied the limitation imposed by different implementations (VLSI, GPU, and CPU) of BCH decoders, and we propose a cascaded BCH code implemented using a hybrid approach to overcome the limitations of the BCH codes. By splitting the implementation across VLSI and GPUs, we have shown in this thesis that this method can provide flexibility over the block size and the bit error to be corrected

Area-Optimized Fully-Flexible BCH Decoder for Multiple GF Dimensions

Recently, there are increasing demands for fully flexible Bose Chaudhuri Hocquenghem (BCH) decoders, which can support different dimensions of Galois fields (GF) operations. As the previous BCH decoders are mainly targeting the fixed GF operations, the conventional techniques are no longer suitable for multiple GF dimensions. For the area-optimized flexible BCH decoders, in this paper, we present several optimization schemes for reducing hardware costs of multi-dimensional GF operations. In the proposed optimizations, we first reformulate the matrix operations in syndrome calculation and Chien search for sharing more common sub-expressions between GF operations having different dimensions. The cell based multi-m GF multiplier is newly introduced for the area-efficient flexible key-equation solver. As case studies, we design several prototype flexible BCH decoders for digital video broadcasting systems and NAND flash memory controllers managing different page sizes. The implementation results show that the proposed fully-flexible BCH decoder architecture remarkably enhances the area-efficiency compared with the conventional solutions.112Ysciescopu

Ein flexibles, heterogenes Bildverarbeitungs-Framework für weltraumbasierte, rekonfigurierbare Datenverarbeitungsmodule

Scientific instruments as payload of current space missions are often equipped with high-resolution sensors. Thereby, especially camera-based instruments produce a vast amount of data. To obtain the desired scientific information, this data usually is processed on ground. Due to the high distance of missions within the solar system, the data rate for downlink to the ground station is strictly limited. The volume of scientific relevant data is usually less compared to the obtained raw data. Therefore, processing already has to be carried out on-board the spacecraft. An example of such an instrument is the Polarimetric and Helioseismic Imager (PHI) on-board Solar Orbiter. For acquisition, storage and processing of images, the instrument is equipped with a Data Processing Module (DPM). It makes use of heterogeneous computing based on a dedicated LEON3 processor in combination with two reconfigurable Xilinx Virtex-4 Field-Programmable Gate Arrays (FPGAs). The thesis will provide an overview of the available space-grade processing components (processors and FPGAs) which fulfill the requirements of deepspace missions. It also presents existing processing platforms which are based upon a heterogeneous system combining processors and FPGAs. This also includes the DPM of the PHI instrument, whose architecture will be introduced in detail. As core contribution of this thesis, a framework will be presented which enables high-performance image processing on such hardware-based systems while retaining software-like flexibility. This framework mainly consists of a variety of modules for hardware acceleration which are integrated seamlessly into the data flow of the on-board software. Supplementary, it makes extensive use of the dynamic in-flight reconfigurability of the used Virtex-4 FPGAs. The flexibility of the presented framework is proven by means of multiple examples from within the image processing of the PHI instrument. The framework is analyzed with respect to processing performance as well as power consumption.Wissenschaftliche Instrumente auf aktuellen Raumfahrtmissionen sind oft mit hochauflösenden Sensoren ausgestattet. Insbesondere kamerabasierte Instrumente produzieren dabei eine große Menge an Daten. Diese werden üblicherweise nach dem Empfang auf der Erde weiterverarbeitet, um daraus wissenschaftlich relevante Informationen zu gewinnen. Aufgrund der großen Entfernung von Missionen innerhalb unseres Sonnensystems ist die Datenrate zur Übertragung an die Bodenstation oft sehr begrenzt. Das Volumen der wissenschaftlich relevanten Daten ist meist deutlich kleiner als die aufgenommenen Rohdaten. Daher ist es vorteilhaft, diese bereits an Board der Sonde zu verarbeiten. Ein Beispiel für solch ein Instrument ist der Polarimetric and Helioseismic Imager (PHI) an Bord von Solar Orbiter. Um die Daten aufzunehmen, zu speichern und zu verarbeiten, ist das Instrument mit einem Data Processing Module (DPM) ausgestattet. Dieses nutzt ein heterogenes Rechnersystem aus einem dedizierten LEON3 Prozessor, zusammen mit zwei rekonfigurierbaren Xilinx Virtex-4 Field-Programmable Gate Arrays (FPGAs). Die folgende Arbeit gibt einen Überblick über verfügbare Komponenten zur Datenverarbeitung (Prozessoren und FPGAs), die den Anforderungen von Raumfahrtmissionen gerecht werden, und stellt einige existierende Plattformen vor, die auf einem heterogenen System aus Prozessor und FPGA basieren. Hierzu gehört auch das Data Processing Module des PHI Instrumentes, dessen Architektur im Verlauf dieser Arbeit beschrieben wird. Als Kernelement der Dissertation wird ein Framework vorgestellt, das sowohl eine performante, als auch eine flexible Bilddatenverarbeitung auf einem solchen System ermöglicht. Dieses Framework besteht aus verschiedenen Modulen zur Hardwarebeschleunigung und bindet diese nahtlos in den Datenfluss der On-Board Software ein. Dabei wird außerdem die Möglichkeit genutzt, die eingesetzten Virtex-4 FPGAs dynamisch zur Laufzeit zu rekonfigurieren. Die Flexibilität des vorgestellten Frameworks wird anhand mehrerer Fallbeispiele aus der Bildverarbeitung von PHI dargestellt. Das Framework wird bezüglich der Verarbeitungsgeschwindigkeit und Energieeffizienz analysiert