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Conference Papers

Open list in Research Information System


A Massively Parallel Algorithm for the Approximate Calculation of Inverse p-th Roots of Large Sparse Matrices

M. Lass, S. Mohr, H. Wiebeler, T. Kühne, C. Plessl, in: Proc. Platform for Advanced Scientific Computing (PASC) Conference, ACM, 2018

Automated Code Acceleration Targeting Heterogeneous OpenCL Devices

H. Riebler, G.F. Vaz, T. Kenter, C. Plessl, in: Proc. ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming (PPoPP), ACM, 2018


OpenCL-based FPGA Design to Accelerate the Nodal Discontinuous Galerkin Method for Unstructured Meshes

T. Kenter, G. Mahale, S. Alhaddad, Y. Grynko, C. Schmitt, A. Afzal, F. Hannig, J. Förstner, C. Plessl, in: Proc. Int. Symp. on Field-Programmable Custom Computing Machines (FCCM), IEEE, 2018

The exploration of FPGAs as accelerators for scientific simulations has so far mostly been focused on small kernels of methods working on regular data structures, for example in the form of stencil computations for finite difference methods. In computational sciences, often more advanced methods are employed that promise better stability, convergence, locality and scaling. Unstructured meshes are shown to be more effective and more accurate, compared to regular grids, in representing computation domains of various shapes. Using unstructured meshes, the discontinuous Galerkin method preserves the ability to perform explicit local update operations for simulations in the time domain. In this work, we investigate FPGAs as target platform for an implementation of the nodal discontinuous Galerkin method to find time-domain solutions of Maxwell's equations in an unstructured mesh. When maximizing data reuse and fitting constant coefficients into suitably partitioned on-chip memory, high computational intensity allows us to implement and feed wide data paths with hundreds of floating point operators. By decoupling off-chip memory accesses from the computations, high memory bandwidth can be sustained, even for the irregular access pattern required by parts of the application. Using the Intel/Altera OpenCL SDK for FPGAs, we present different implementation variants for different polynomial orders of the method. In different phases of the algorithm, either computational or bandwidth limits of the Arria 10 platform are almost reached, thus outperforming a highly multithreaded CPU implementation by around 2x.


Flexible FPGA design for FDTD using OpenCL

T. Kenter, J. Förstner, C. Plessl, in: Proc. Int. Conf. on Field Programmable Logic and Applications (FPL), IEEE, 2017



Confidentiality and Authenticity for Distributed Version Control Systems - A Mercurial Extension

M. Lass, D. Leibenger, C. Sorge, in: Proc. 41st Conference on Local Computer Networks (LCN), IEEE, 2016

Version Control Systems (VCS) are a valuable tool for software development and document management. Both client/server and distributed (Peer-to-Peer) models exist, with the latter (e.g., Git and Mercurial) becoming increasingly popular. Their distributed nature introduces complications, especially concerning security: it is hard to control the dissemination of contents stored in distributed VCS as they rely on replication of complete repositories to any involved user. We overcome this issue by designing and implementing a concept for cryptography-enforced access control which is transparent to the user. Use of field-tested schemes (end-to-end encryption, digital signatures) allows for strong security, while adoption of convergent encryption and content-defined chunking retains storage efficiency. The concept is seamlessly integrated into Mercurial---respecting its distributed storage concept---to ensure practical usability and compatibility to existing deployments.

Microdisk Cavity FDTD Simulation on FPGA using OpenCL

T. Kenter, C. Plessl, in: Proc. Workshop on Heterogeneous High-performance Reconfigurable Computing (H2RC), 2016

Opportunities for deferring application partitioning and accelerator synthesis to runtime (extended abstract)

T. Kenter, G.F. Vaz, H. Riebler, C. Plessl, in: Workshop on Reconfigurable Computing (WRC), 2016

Performance-centric scheduling with task migration for a heterogeneous compute node in the data center

A. Lösch, T. Beisel, T. Kenter, C. Plessl, M. Platzner, in: Proceedings of the 2016 Design, Automation & Test in Europe Conference & Exhibition (DATE), EDA Consortium / IEEE, 2016, pp. 912-917

Using Approximate Computing in Scientific Codes

M. Lass, T. Kühne, C. Plessl, in: Workshop on Approximate Computing (AC), 2016

Using Just-in-Time Code Generation for Transparent Resource Management in Heterogeneous Systems

H. Riebler, G.F. Vaz, C. Plessl, E.M.G. Trainiti, G.C. Durelli, C. Bolchini, in: Proc. HiPEAC Workshop on Reonfigurable Computing (WRC), 2016

Using Just-in-Time Code Generation for Transparent Resource Management in Heterogeneous Systems

H. Riebler, G.F. Vaz, C. Plessl, E.M.G.. Trainiti, G.C. Durelli, E. Del Sozzo, M.D.. Santambrogio, C. Bolchini, in: Proceedings of International Forum on Research and Technologies for Society and Industry (RTSI), IEEE, 2016, pp. 1-5

Hardware accelerators are becoming popular in academia and industry. To move one step further from the state-of-the-art multicore plus accelerator approaches, we present in this paper our innovative SAVEHSA architecture. It comprises of a heterogeneous hardware platform with three different high-end accelerators attached over PCIe (GPGPU, FPGA and Intel MIC). Such systems can process parallel workloads very efficiently whilst being more energy efficient than regular CPU systems. To leverage the heterogeneity, the workload has to be distributed among the computing units in a way that each unit is well-suited for the assigned task and executable code must be available. To tackle this problem we present two software components; the first can perform resource allocation at runtime while respecting system and application goals (in terms of throughput, energy, latency, etc.) and the second is able to analyze an application and generate executable code for an accelerator at runtime. We demonstrate the first proof-of-concept implementation of our framework on the heterogeneous platform, discuss different runtime policies and measure the introduced overheads.


Easy-to-Use On-The-Fly Binary Program Acceleration on Many-Cores

M. Damschen, C. Plessl, in: Proceedings of the 5th International Workshop on Adaptive Self-tuning Computing Systems (ADAPT), 2015

Improving Packet Processing Performance in the ATLAS FELIX Project – Analysis and Optimization of a Memory-Bounded Algorithm

J. Schumacher, J. T. Anderson, A. Borga, H. Boterenbrood, H. Chen, K. Chen, G. Drake, D. Francis, B. Gorini, F. Lanni, G. Lehmann-Miotto, L. Levinson, J. Narevicius, C. Plessl, A. Roich, S. Ryu, F. P. Schreuder, W. Vandelli, J. Vermeulen, J. Zhang, in: Proc. Int. Conf. on Distributed Event-Based Systems (DEBS), ACM, 2015


Transparent offloading of computational hotspots from binary code to Xeon Phi

M. Damschen, H. Riebler, G.F. Vaz, C. Plessl, in: Proceedings of the 2015 Conference on Design, Automation and Test in Europe (DATE), EDA Consortium / IEEE, 2015, pp. 1078-1083

In this paper, we study how binary applications can be transparently accelerated with novel heterogeneous computing resources without requiring any manual porting or developer-provided hints. Our work is based on Binary Acceleration At Runtime (BAAR), our previously introduced binary acceleration mechanism that uses the LLVM Compiler Infrastructure. BAAR is designed as a client-server architecture. The client runs the program to be accelerated in an environment, which allows program analysis and profiling and identifies and extracts suitable program parts to be offloaded. The server compiles and optimizes these offloaded program parts for the accelerator and offers access to these functions to the client with a remote procedure call (RPC) interface. Our previous work proved the feasibility of our approach, but also showed that communication time and overheads limit the granularity of functions that can be meaningfully offloaded. In this work, we motivate the importance of a lightweight, high-performance communication between server and client and present a communication mechanism based on the Message Passing Interface (MPI). We evaluate our approach by using an Intel Xeon Phi 5110P as the acceleration target and show that the communication overhead can be reduced from 40% to 10%, thus enabling even small hotspots to benefit from offloading to an accelerator.


Deferring Accelerator Offloading Decisions to Application Runtime

G.F. Vaz, H. Riebler, T. Kenter, C. Plessl, in: Proceedings of the International Conference on ReConFigurable Computing and FPGAs (ReConFig), IEEE, 2014, pp. 1-8

Reconfigurable architectures provide an opportunityto accelerate a wide range of applications, frequentlyby exploiting data-parallelism, where the same operations arehomogeneously executed on a (large) set of data. However, whenthe sequential code is executed on a host CPU and only dataparallelloops are executed on an FPGA coprocessor, a sufficientlylarge number of loop iterations (trip counts) is required, such thatthe control- and data-transfer overheads to the coprocessor canbe amortized. However, the trip count of large data-parallel loopsis frequently not known at compile time, but only at runtime justbefore entering a loop. Therefore, we propose to generate codeboth for the CPU and the coprocessor, and to defer the decisionwhere to execute the appropriate code to the runtime of theapplication when the trip count of the loop can be determinedjust at runtime. We demonstrate how an LLVM compiler basedtoolflow can automatically insert appropriate decision blocks intothe application code. Analyzing popular benchmark suites, weshow that this kind of runtime decisions is often applicable. Thepractical feasibility of our approach is demonstrated by a toolflowthat automatically identifies loops suitable for vectorization andgenerates code for the FPGA coprocessor of a Convey HC-1. Thetoolflow adds decisions based on a comparison of the runtimecomputedtrip counts to thresholds for specific loops and alsoincludes support to move just the required data to the coprocessor.We evaluate the integrated toolflow with characteristic loopsexecuted on different input data sizes.

Kernel-Centric Acceleration of High Accuracy Stereo-Matching

T. Kenter, H. Schmitz, C. Plessl, in: Proceedings of the International Conference on ReConFigurable Computing and FPGAs (ReConFig), IEEE, 2014, pp. 1-8

Stereo-matching algorithms recently received a lot of attention from the FPGA acceleration community. Presented solutions range from simple, very resource efficient systems with modest matching quality for small embedded systems to sophisticated algorithms with several processing steps, implemented on big FPGAs. In order to achieve high throughput, most implementations strongly focus on pipelining and data reuse between different computation steps. This approach leads to high efficiency, but limits the supported computation patterns and due the high integration of the implementation, adaptions to the algorithm are difficult. In this work, we present a stereo-matching implementation, that starts by offloading individual kernels from the CPU to the FPGA. Between subsequent compute steps on the FPGA, data is stored off-chip in on-board memory of the FPGA accelerator card. This enables us to accelerate the AD-census algorithm with cross-based aggregation and scanline optimization for the first time without algorithmic changes and for up to full HD image dimensions. Analyzing throughput and bandwidth requirements, we outline some trade-offs that are involved with this approach, compared to tighter integration of more kernel loops into one design.

Partitioning and Vectorizing Binary Applications for a Reconfigurable Vector Computer

T. Kenter, G.F. Vaz, C. Plessl, in: Proceedings of the International Symposium on Reconfigurable Computing: Architectures, Tools, and Applications (ARC), Springer International Publishing, 2014, pp. 144-155

In order to leverage the use of reconfigurable architectures in general-purpose computing, quick and automated methods to find suitable accelerator designs are required. We tackle this challenge in both regards. In order to avoid long synthesis times, we target a vector copro- cessor, implemented on the FPGAs of a Convey HC-1. Previous studies showed that existing tools were not able to accelerate a real-world application with low effort. We present a toolflow to automatically identify suitable loops for vectorization, generate a corresponding hardware/software bipartition, and generate coprocessor code. Where applicable, we leverage outer-loop vectorization. We evaluate our tools with a set of characteristic loops, systematically analyzing different dependency and data layout properties.

Reconstructing AES Key Schedules from Decayed Memory with FPGAs

H. Riebler, T. Kenter, C. Plessl, C. Sorge, in: Proceedings of Field-Programmable Custom Computing Machines (FCCM), IEEE, 2014, pp. 222-229

In this paper, we study how AES key schedules can be reconstructed from decayed memory. This operation is a crucial and time consuming operation when trying to break encryption systems with cold-boot attacks. In software, the reconstruction of the AES master key can be performed using a recursive, branch-and-bound tree-search algorithm that exploits redundancies in the key schedule for constraining the search space. In this work, we investigate how this branch-and-bound algorithm can be accelerated with FPGAs. We translated the recursive search procedure to a state machine with an explicit stack for each recursion level and create optimized datapaths to accelerate in particular the processing of the most frequently accessed tree levels. We support two different decay models, of which especially the more realistic non-idealized asymmetric decay model causes very high runtimes in software. Our implementation on a Maxeler dataflow computing system outperforms a software implementation for this model by up to 27x, which makes cold-boot attacks against AES practical even for high error rates.

Runtime Resource Management in Heterogeneous System Architectures: The SAVE Approach

G. C. Durelli, M. Pogliani, A. Miele, C. Plessl, H. Riebler, G.F. Vaz, M. D. Santambrogio, C. Bolchini, in: Proc. Int. Symp. on Parallel and Distributed Processing with Applications (ISPA), IEEE, 2014, pp. 142-149


SAVE: Towards efficient resource management in heterogeneous system architectures

G. C. Durelli, M. Copolla, K. Djafarian, G. Koranaros, A. Miele, M. Paolino, O. Pell, C. Plessl, M. D. Santambrogio, C. Bolchini, in: Proc. Int. Conf. on Reconfigurable Computing: Architectures, Tools and Applications (ARC), Springer, 2014



FPGA-accelerated Key Search for Cold-Boot Attacks against AES

H. Riebler, T. Kenter, C. Sorge, C. Plessl, in: Proceedings of the International Conference on Field-Programmable Technology (FPT), IEEE, 2013, pp. 386-389

Cold-boot attacks exploit the fact that DRAM contents are not immediately lost when a PC is powered off. Instead the contents decay rather slowly, in particular if the DRAM chips are cooled to low temperatures. This effect opens an attack vector on cryptographic applications that keep decrypted keys in DRAM. An attacker with access to the target computer can reboot it or remove the RAM modules and quickly copy the RAM contents to non-volatile memory. By exploiting the known cryptographic structure of the cipher and layout of the key data in memory, in our application an AES key schedule with redundancy, the resulting memory image can be searched for sections that could correspond to decayed cryptographic keys; then, the attacker can attempt to reconstruct the original key. However, the runtime of these algorithms grows rapidly with increasing memory image size, error rate and complexity of the bit error model, which limits the practicability of the approach.In this work, we study how the algorithm for key search can be accelerated with custom computing machines. We present an FPGA-based architecture on a Maxeler dataflow computing system that outperforms a software implementation up to 205x, which significantly improves the practicability of cold-attacks against AES.

On-The-Fly Computing: A Novel Paradigm for Individualized IT Services

M. Happe, P. Kling, C. Plessl, M. Platzner, F. Meyer auf der Heide, in: Proceedings of the 9th IEEE Workshop on Software Technology for Future embedded and Ubiquitous Systems (SEUS), IEEE, 2013

In this paper we introduce “On-The-Fly Computing”, our vision of future IT services that will be provided by assembling modular software components available on world-wide markets. After suitable components have been found, they are automatically integrated, configured and brought to execution in an On-The-Fly Compute Center. We envision that these future compute centers will continue to leverage three current trends in large scale computing which are an increasing amount of parallel processing, a trend to use heterogeneous computing resources, and—in the light of rising energy cost—energy-efficiency as a primary goal in the design and operation of computing systems. In this paper, we point out three research challenges and our current work in these areas.

Parallel Macro Pipelining on the Intel SCC Many-Core Computer

T. Suess, A. Schoenrock, S. Meisner, C. Plessl, in: Proc. Int. Symp. on Parallel and Distributed Processing Workshops (IPDPSW), IEEE Computer Society, 2013, pp. 64-73



A Data Driven Science Gateway for Computational Workflows

R. Grunzke, G. Birkenheuer, D. Blunk, S. Breuers, A. Brinkmann, S. Gesing, S. Herres-Pawlis, O. Kohlbacher, J. Krüger, M. Kruse, R. Müller-Pfefferkorn, P. Schäfer, B. Schuller, T. Steinke, A. Zink, in: Proc. UNICORE Summit, 2012

Convey Vector Personalities – FPGA Acceleration with an OpenMP-like Effort?

B. Meyer, J. Schumacher, C. Plessl, J. Förstner, in: Proc. Int. Conf. on Field Programmable Logic and Applications (FPL), IEEE, 2012, pp. 189-196

Although the benefits of FPGAs for accelerating scientific codes are widely acknowledged, the use of FPGA accelerators in scientific computing is not widespread because reaping these benefits requires knowledge of hardware design methods and tools that is typically not available with domain scientists. A promising but hardly investigated approach is to develop tool flows that keep the common languages for scientific code (C,C++, and Fortran) and allow the developer to augment the source code with OpenMPlike directives for instructing the compiler which parts of the application shall be offloaded the FPGA accelerator. In this work we study whether the promise of effective FPGA acceleration with an OpenMP-like programming effort can actually be held. Our target system is the Convey HC-1 reconfigurable computer for which an OpenMP-like programming environment exists. As case study we use an application from computational nanophotonics. Our results show that a developer without previous FPGA experience could create an FPGA-accelerated application that is competitive to an optimized OpenMP-parallelized CPU version running on a two socket quad-core server. Finally, we discuss our experiences with this tool flow and the Convey HC-1 from a productivity and economic point of view.

Eight Ways to put your FPGA on Fire – A Systematic Study of Heat Generators

M. Happe, H. Hangmann, A. Agne, C. Plessl, in: Proceedings of the International Conference on Reconfigurable Computing and FPGAs (ReConFig), IEEE, 2012, pp. 1-8

Due to the continuously shrinking device structures and increasing densities of FPGAs, thermal aspects have become the new focus for many research projects over the last years. Most researchers rely on temperature simulations to evaluate their novel thermal management techniques. However, the accuracy of the simulations is to some extent questionable and they require a high computational effort if a detailed thermal model is used.For experimental evaluation of real-world temperature management methods, often synthetic heat sources are employed. Therefore, in this paper we investigated the question if we can create significant rises in temperature on modern FPGAs to enable future evaluation of thermal management techniques based on experiments in contrast to simulations. Therefore, we have developed eight different heat-generating cores that use different subsets of the FPGA resources. Our experimental results show that, according to the built-in thermal diode of our Xilinx Virtex-5 FPGA, we can increase the chip temperature by 134 degree C in less than 12 minutes by only utilizing about 21% of the slices.

Exploration of Ring Oscillator Design Space for Temperature Measurements on FPGAs

C. Rüthing, M. Happe, A. Agne, C. Plessl, in: Proceedings of the International Conference on Field Programmable Logic and Applications (FPL), IEEE, 2012, pp. 559-562

While numerous publications have presented ring oscillator designs for temperature measurements a detailed study of the ring oscillator's design space is still missing. In this work, we introduce metrics for comparing the performance and area efficiency of ring oscillators and a methodology for determining these metrics. As a result, we present a systematic study of the design space for ring oscillators for a Xilinx Virtex-5 platform FPGA.

Hardware/Software Platform for Self-aware Compute Nodes

M. Happe, A. Agne, C. Plessl, M. Platzner, in: Proceedings of the Workshop on Self-Awareness in Reconfigurable Computing Systems (SRCS), 2012, pp. 8-9

Pragma based parallelization - Trading hardware efficiency for ease of use?

T. Kenter, C. Plessl, H. Schmitz, in: Proceedings of the International Conference on ReConFigurable Computing and FPGAs (ReConFig), IEEE, 2012, pp. 1-8

One major obstacle for a wide spread FPGA usage in general-purpose computing is the development tool flow that requires much higher effort than for pure software solutions. Convey Computer promises a solution to this problem for their HC-1 platform, where the FPGAs are configured to run as a vector processor and the software source code can be annotated with pragmas that guide an automated vectorization process. We investigate this approach for a stereo matching algorithm that has abundant parallelism and a number of different computational patterns. We note that for this case study the automated vectorization in its current state doesn’t hold its productivity promise. However, we also show that using the Vector Personality can yield a significant speedups compared to CPU implementations in two of three investigated phases of the algorithm. Those speedups don’t match custom FPGA implementations, but can come with much reduced development effort.

Programming and Scheduling Model for Supporting Heterogeneous Accelerators in Linux

T. Beisel, T. Wiersema, C. Plessl, A. Brinkmann, in: Proc. Workshop on Computer Architecture and Operating System Co-design (CAOS), 2012

Turning control flow graphs into function calls: Code generation for heterogeneous architectures

P. Barrio, C. Carreras, R. Sierra, T. Kenter, C. Plessl, in: Proceedings of the International Conference on High Performance Computing and Simulation (HPCS), IEEE, 2012, pp. 559-565

Heterogeneous machines are gaining momentum in the High Performance Computing field, due to the theoretical speedups and power consumption. In practice, while some applications meet the performance expectations, heterogeneous architectures still require a tremendous effort from the application developers. This work presents a code generation method to port codes into heterogeneous platforms, based on transformations of the control flow into function calls. The results show that the cost of the function-call mechanism is affordable for the tested HPC kernels. The complete toolchain, based on the LLVM compiler infrastructure, is fully automated once the sequential specification is provided.


Cooperative multitasking for heterogeneous accelerators in the Linux Completely Fair Scheduler

T. Beisel, T. Wiersema, C. Plessl, A. Brinkmann, in: Proc. Int. Conf. on Application-Specific Systems, Architectures, and Processors (ASAP), IEEE Computer Society, 2011, pp. 223-226


Estimation and Partitioning for CPU-Accelerator Architectures

T. Kenter, C. Plessl, M. Platzner, M. Kauschke, in: Intel European Research and Innovation Conference, 2011

Just-in-time Instruction Set Extension – Feasibility and Limitations for an FPGA-based Reconfigurable ASIP Architecture

M. Grad, C. Plessl, in: Proc. Reconfigurable Architectures Workshop (RAW), IEEE Computer Society, 2011, pp. 278-285


Measuring and Predicting Temperature Distributions on FPGAs at Run-Time

M. Happe, A. Agne, C. Plessl, in: Proceedings of the 2011 International Conference on Reconfigurable Computing and FPGAs (ReConFig), IEEE, 2011, pp. 55-60

In the next decades, hybrid multi-cores will be the predominant architecture for reconfigurable FPGA-based systems. Temperature-aware thread mapping strategies are key for providing dependability in such systems. These strategies rely on measuring the temperature distribution and redicting the thermal behavior of the system when there are changes to the hardware and software running on the FPGA. While there are a number of tools that use thermal models to predict temperature distributions at design time, these tools lack the flexibility to autonomously adjust to changing FPGA configurations. To address this problem we propose a temperature-aware system that empowers FPGA-based reconfigurable multi-cores to autonomously predict the on-chip temperature distribution for pro-active thread remapping. Our system obtains temperature measurements through a self-calibrating grid of sensors and uses area constrained heat-generating circuits in order to generate spatial and temporal temperature gradients. The generated temperature variations are then used to learn the free parameters of the system's thermal model. The system thus acquires an understanding of its own thermal characteristics. We implemented an FPGA system containing a net of 144 temperature sensors on a Xilinx Virtex-6 LX240T FPGA that is aware of its thermal model. Finally, we show that the temperature predictions vary less than 0.72 degree C on average compared to the measured temperature distributions at run-time.

Performance Estimation Framework for Automated Exploration of CPU-Accelerator Architectures

T. Kenter, M. Platzner, C. Plessl, M. Kauschke, in: Proc. Int. Symp. on Field-Programmable Gate Arrays (FPGA), ACM, 2011, pp. 177-180


Transformation of scientific algorithms to parallel computing code: subdomain support in a MPI-multi-GPU backend

B. Meyer, C. Plessl, J. Förstner, in: Symp. on Application Accelerators in High Performance Computing (SAAHPC), IEEE Computer Society, 2011, pp. 60-63



An Open Source Circuit Library with Benchmarking Facilities

M. Grad, C. Plessl, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2010, pp. 144-150

Configurable Processor Architectures: History and Trends

D. Andrews, C. Plessl, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2010, pp. 165

Performance Estimation for the Exploration of CPU-Accelerator Architectures

T. Kenter, M. Platzner, C. Plessl, M. Kauschke, in: Proc. Workshop on Architectural Research Prototyping (WARP), International Symposium on Computer Architecture (ISCA), 2010

Pruning the Design Space for Just-In-Time Processor Customization

M. Grad, C. Plessl, in: Proc. Int. Conf. on ReConFigurable Computing and FPGAs (ReConFig), IEEE Computer Society, 2010, pp. 67-72


Reconfigurable Nodes for Future Networks

A. Keller, B. Plattner, E. Lübbers, M. Platzner, C. Plessl, in: Proc. IEEE Globecom Workshop on Network of the Future (FutureNet), IEEE, 2010, pp. 372-376


Rupeas: Ruby Powered Event Analysis DSL

M. Woehrle, C. Plessl, L. Thiele, in: Proc. Int. Conf. Networked Sensing Systems (INSS), IEEE, 2010, pp. 245-248


Towards Adaptive Networking for Embedded Devices based on Reconfigurable Hardware

E. Lübbers, M. Platzner, C. Plessl, A. Keller, B. Plattner, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2010, pp. 225-231

Using Shared Library Interposing for Transparent Acceleration in Systems with Heterogeneous Hardware Accelerators

T. Beisel, M. Niekamp, C. Plessl, in: Proc. Int. Conf. on Application-Specific Systems, Architectures, and Processors (ASAP), IEEE Computer Society, 2010, pp. 65-72



An Accelerator for k-th Nearest Neighbor Thinning Based on the IMORC Infrastructure

T. Schumacher, C. Plessl, M. Platzner, in: Proc. Int. Conf. on Field Programmable Logic and Applications (FPL), IEEE, 2009, pp. 338-344

Communication Performance Characterization for Reconfigurable Accelerator Design on the XD1000

T. Schumacher, T. Süß, C. Plessl, M. Platzner, in: Proc. Int. Conf. on ReConFigurable Computing and FPGAs (ReConFig), IEEE Computer Society, 2009, pp. 119-124


EvoCaches: Application-specific Adaptation of Cache Mapping

P. Kaufmann, C. Plessl, M. Platzner, in: Proc. NASA/ESA Conference on Adaptive Hardware and Systems (AHS), IEEE Computer Society, 2009, pp. 11-18

IMORC: Application Mapping, Monitoring and Optimization for High-Performance Reconfigurable Computing

T. Schumacher, C. Plessl, M. Platzner, in: Proc. Int. Symp. on Field-Programmable Custom Computing Machines (FCCM), IEEE Computer Society, 2009, pp. 275-278

Mapping applications that consist of a collection of cores to FPGA accelerators and optimizing their performance is a challenging task in high performance reconfigurable computing. We present IMORC, an architectural template and highly versatile on-chip interconnect. IMORC links provide asynchronous FIFOs and bitwidth conversion which allows for flexibly composing accelerators from cores running at full speed within their own clock domains, thus facilitating the re-use of cores and portability. Further, IMORC inserts performance counters for monitoring runtime data. In this paper, we first introduce the IMORC architectural template and the on-chip interconnect, and then demonstrate IMORC on the example of accelerating the k-th nearest neighbor thinning problem on an XD1000 reconfigurable computing system. Using IMORC's monitoring infrastructure, we gain insights into the data-dependent behavior of the application which, in turn, allow for optimizing the accelerator.

PermaDAQ: A Scientific Instrument for Precision Sensing and Data Recovery in Environmental Extremes

J. Beutel, S. Gruber, A. Hasler, R. Lim, A. Meier, C. Plessl, I. Talzi, L. Thiele, C. Tschudin, M. Woehrle, M. Yuecel, in: Proc. Int. Conf. on Information Processing in Sensor Networks (IPSN), IEEE Computer Society, 2009, pp. 265-276

Woolcano: An Architecture and Tool Flow for Dynamic Instruction Set Extension on Xilinx Virtex-4 FX

M. Grad, C. Plessl, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2009, pp. 319-322


A Hardware Accelerator for k-th Nearest Neighbor Thinning

T. Schumacher, R. Meiche, P. Kaufmann, E. Lübbers, C. Plessl, M. Platzner, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2008, pp. 245-251

EvAnT: Analysis and Checking of event traces for Wireless Sensor Networks

M. Woehrle, C. Plessl, R. Lim, J. Beutel, L. Thiele, in: IEEE Int. Conf. on Sensor Networks, Ubiquitous, and Trustworthy Computing (SUTC), IEEE Computer Society, 2008, pp. 201-208


IMORC: An infrastructure for performance monitoring and optimization of reconfigurable computers

T. Schumacher, C. Plessl, M. Platzner, in: Many-core and Reconfigurable Supercomputing Conference (MRSC), 2008


Automated Wireless Sensor Network Testing

J. Beutel, M. Dyer, R. Lim, C. Plessl, M. Woehrle, M. Yuecel, L. Thiele, in: Proc. Int. Conf. Networked Sensing Systems (INSS), IEEE, 2007, pp. 303-303


Increasing the Reliability of Wireless Sensor Networks with a Distributed Testing Framework

M. Woehrle, C. Plessl, J. Beutel, L. Thiele, in: Proc. Workshop on Embedded Networked Sensors (EmNets), ACM, 2007, pp. 93-97



Optimal Temporal Partitioning based on Slowdown and Retiming

C. Plessl, M. Platzner, L. Thiele, in: Proc. Int. Conf. on Field Programmable Technology (ICFPT), IEEE Computer Society, 2006, pp. 345-348

This paper presents a novel method for optimal temporal partitioning of sequential circuits for time-multiplexed reconfigurable architectures. The method bases on slowdown and retiming and maximizes the circuit's performance during execution while restricting the size of the partitions to respect the resource constraints of the reconfigurable architecture. We provide a mixed integer linear program (MILP) formulation of the problem, which can be solved exactly. In contrast to related work, our approach optimizes performance directly, takes structural modifications of the circuit into account, and is extensible. We present the application of the new method to temporal partitioning for a coarse-grained reconfigurable architecture.


Zippy – A coarse-grained reconfigurable array with support for hardware virtualization

C. Plessl, M. Platzner, in: Proc. Int. Conf. on Application-Specific Systems, Architectures, and Processors (ASAP), IEEE Computer Society, 2005, pp. 213-218

This paper motivates the use of hardware virtualization on coarse-grained reconfigurable architectures. We introduce Zippy, a coarse-grained multi-context hybrid CPU with architectural support for efficient hardware virtualization. The architectural details and the corresponding tool flow are outlined. As a case study, we compare the non-virtualized and the virtualized execution of an ADPCM decoder.


Virtualization of Hardware – Introduction and Survey

C. Plessl, M. Platzner, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2004, pp. 63-69


Co-simulation of a Hybrid Multi-Context Architecture

R. Enzler, C. Plessl, M. Platzner, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2003, pp. 174-180

TKDM – A Reconfigurable Co-processor in a PC's Memory Slot

C. Plessl, M. Platzner, in: Proc. Int. Conf. on Field Programmable Technology (ICFPT), IEEE Computer Society, 2003, pp. 252-259

This paper presents TKDM, a PC-based high-performance reconfigurable computing environment. The TKDM hardware consists of an FPGA module that uses the DIMM (dual inline memory module) bus for high-bandwidth and low-latency communication with the host CPU. The system's firmware is integrated with the Linux host operating system and offers functions for data communication and FPGA reconfiguration. The intended use of TKDM is that of a dynamically reconfigurable co-processor for data streaming applications. The system's firmware can be customized for specific application domains to facilitate simple and easy-to-use programming interfaces.

Virtualizing Hardware with Multi-Context Reconfigurable Arrays

R. Enzler, C. Plessl, M. Platzner, in: Proc. Int. Conf. on Field Programmable Logic and Applications (FPL), Springer, 2003, pp. 151-160

In contrast to processors, current reconfigurable devices totally lack programming models that would allow for device independent compilation and forward compatibility. The key to overcome this limitation is hardware virtualization. In this paper, we resort to a macro-pipelined execution model to achieve hardware virtualization for data streaming applications. As a hardware implementation we present a hybrid multi-context architecture that attaches a coarse-grained reconfigurable array to a host CPU. A co-simulation framework enables cycle-accurate simulation of the complete architecture. As a case study we map an FIR filter to our virtualized hardware model and evaluate different designs. We discuss the impact of the number of contexts and the feature of context state on the speedup and the CPU load.


Custom Computing Machines for the Set Covering Problem

C. Plessl, M. Platzner, in: Proc. Int. Symp. on Field-Programmable Custom Computing Machines (FCCM), IEEE Computer Society, 2002, pp. 163-172

We present instance-specific custom computing machines for the set covering problem. Four accelerator architectures are developed that implement branch \& bound in 3-valued logic and many of the deduction techniques found in software solvers. We use set covering benchmarks from two-level logic minimization and Steiner triple systems to derive and discuss experimental results. The resulting raw speedups are in the order of four magnitudes on average. Finally, we propose a hybrid solver architecture that combines the raw speed of instance-specific reconfigurable hardware with flexible bounding schemes implemented in software.

Partially Reconfigurable Cores for Xilinx Virtex

M. Dyer, C. Plessl, M. Platzner, in: Proc. Int. Conf. on Field Programmable Logic and Applications (FPL), Springer, 2002, pp. 292-301

Recent generations of high-density and high-speed FPGAs provide a sufficient capacity for implementing complete configurable systems on a chip (CSoCs). Hybrid CPUs that combine standard CPU cores with reconfigurable coprocessors are an important subclass of CSoCs. With partially reconfigurable FPGAs, coprocessors can be loaded on demand while the CPU remains running. However, the lack of high-level design tools for partial reconfiguration makes practical implementations a challenging task. In this paper, we introduce a design flow to implement hybrid processors on Xilinx Virtex. The design flow is based on two techniques, virtual sockets and feed-through components, and can efficiently generate partial configurations from industry-quality cores. We discuss the design flow and present a fully operational audio streaming prototype to demonstrate its feasibility.

Reconfigurable Hardware in Wearable Computing Nodes

C. Plessl, R. Enzler, H. Walder, J. Beutel, M. Platzner, L. Thiele, in: Proc. Int. Symp. on Wearable Computers (ISWC), IEEE Computer Society, 2002, pp. 215-222

Wearable computers are embedded into the mobile environment of the human body. A design challenge for wearable systems is to combine the high performance required for tasks such as video decoding with low energy consumption required to maximize battery runtimes and the flexibility demanded by the dynamics of the environment and the applications. In this paper, we demonstrate that reconfigurable hardware technology is able to answer this challenge. We present the concept and the prototype implementation of an autonomous wearable unit with reconfigurable modules (WURM). We discuss two experiments that show the uses of reconfigurable hardware in WURM: ASICs-on-demand and adaptive interfaces. Finally, we develop and evaluate task placement techniques used in the operating system layer of WURM.


Instance-Specific Accelerators for Minimum Covering

C. Plessl, M. Platzner, in: Proc. Int. Conf. on Engineering of Reconfigurable Systems and Algorithms (ERSA), CSREA Press, 2001, pp. 85-91

Reconfigurable Processors for Handhelds and Wearables: Application Analysis

R. Enzler, M. Platzner, C. Plessl, L. Thiele, G. Tröster, in: Reconfigurable Technology: FPGAs and Reconfigurable Processors for Computing and Communications III, 2001, pp. 135-146

In this paper, we present the analysis of applications from the domain of handheld and wearable computing. This analysis is the first step to derive and evaluate design parameters for dynamically reconfigurable processors. We discuss the selection of representative benchmarks for handhelds and wearables and group the applications into multimedia, communications, and cryptography programs. We simulate the applications on a cycle-accurate processor simulator and gather statistical data such as instruction mix, cache hit rates and memory requirements for an embedded processor model. A breakdown of the executed cycles into different functions identifies the most compute-intensive code sections - the kernels. Then, we analyze the applications and discuss parameters that strongly influence the design of dynamically reconfigurable processors. Finally, we outline the construction of a parameterizable simulation model for a reconfigurable unit that is attached to a processor core.

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