Customized Parallel
Computing (CPC) group

This is the home page of the CPC research group of Tampere University. The group's name in Finnish is Räätälöity rinnakkaislaskenta. CPC's main research focus is on design and programming methodologies of customized parallel computing platforms and real time implementations of challenging algorithms.


In addition to publications and theses listed here as academic contributions, CPC has also made major open source contributions in the field of portable and customized heterogeneous computing: The group has created OpenASIP and Portable Computing Language (pocl) which are being used widely as research platforms and even for product use cases. CPC also created the prototype HIPCL tool which evolved into chipStar, a portable CUDA/HIP implementation using open standards.


An algorithm domain with extreme computational demands that CPC has been very interested in the past years is real time ray tracing. A separate focus group was formed for finding algorithmic, parallel/heterogeneous implementation and custom hardware solutions for its challenges in 2015. The group's web pages are here.

The CPC group in Fall 2023.

News

April 29th, 2024: The Impact of Wireless Channel Impairments on Computer Vision Accuracy in WCNC 2024

When offloading computer vision (CV) computation from a small device, such as a drone, to a remote server, a stream of images needs to be sent over a wireless network channel. Traditional entropy-coded bitstreams, such as JPEG, transmitted via a digital channel are prone to a so-called “digital cliff”: A sudden drop in the reconstructed image quality due to data corruption caused by channel noise and lost packets. To circumvent the digital cliff, Linear Coding and Transmission schemes (LCT) were pioneered by SoftCast in 2010, in which the reconstructed image quality degrades smoothly with increased amount of channel impairments. So far, however, the impact of LCT and channel impairments on CV accuracy has been studied only minimally. Jakub Žádník recently presented a paper “Performance of Linear Coding and Transmission in Low-Latency Computer Vision Offloading” at the WCNC 2024 conference in Dubai (UAE) in which he studies the impact of LCT processing, wireless channel noise and packet losses on the accuracy of semantic segmentation and object detection tasks. The absence of the digital cliff in the task accuracy was confirmed via a thorough evaluation over a wide range of LCT configurations. The findings were further strengthened by a realistic 5G channel simulation and retraining the CV tasks to account for the distortions caused by LCT and noisy channel.

April 12th, 2024: OpenCL pipe specification improvements in IWOCL 2024

OpenCL Pipe is a memory object used for passing data between kernels. It is useful in streaming style applications, where data is forwarded from one task to another. Since the pipe can be implemented in multiple ways, and OpenCL is intended as a programming model for heterogeneous platforms, the performance of the pipe implementations can vary heavily. The PhD thesis work of Topi Leppänen has resulted in insights on how the pipe specification could be improved especially in the context of FPGAs. These findings, along with suggestions for the OpenCL specification, were presented in IWOCL 2024 by Topi. Read the publication here.

April 5th, 2024: Adding fault tolerance to OpenCL

The modern computing landscape includes a variety of platforms. In addition to general-purpose devices, specialized processors are used to increase efficiency in various application domains and use cases. The OpenCL standard presents a unified way to program these heterogeneous devices, and the CPC group's PoCL is a vendor-independent, open-source implementation of the standard. In his MSc thesis "Adding fault tolerance to OpenCL" (2023) Robin Bijl added a mechanism to achieve robust computation with PoCL. This allows fault tolerance and reliable computing even in the context of heterogeneous platforms. Read the thesis here.

December 11th, 2023: Improving IoT device capabilities by offloading OpenCL kernels to edge servers

The Internet of things (IoT) consists of an enormous amount of devices with their size varying from large to extremely tiny. While it may be desirable to have complex functionalities in even the tiniest devices, this is often not feasible simply due to the lack of available resources. However, offloading the computation to a (nearby) server or a larger device enables sharing of the resources and seemingly allows even small devices to perform demanding computations. In his MSc thesis "Offloading Computation with a Minimized OpenCL Runtime from a Nano Drone" (2022) Jyry Uitto created a proof-of-concept implementation of a nano drone that can offload OpenCL kernel execution onto an edge server. Read the thesis here.

November 30th, 2023: Dual-IS article in IEEE TC

Static multi-issue processors exploit instruction level parallelism efficiently thanks to the lack of dynamic hardware that schedules instructions during run time. However, their instruction stream energy consumption is significantly higher than that of their dynamic multi- or single-issue counterparts. Processor designers must choose between the benefits of static multi-issue capabilities and higher code density, but is it too much to ask for both? In our latest article, we introduce an energy-efficient dual-mode (RISC-V single-issue and an exposed datapath VLIW) architecture for leveraging instruction level parallelism statically when available in the program, without suffering from VLIW’s poor code density when there’s a lack of it. The flexibility of the architecture is utilized by a novel compilation method that can generate code for both instruction sets with fine-grained mode switching. Read more in the article.

November 16th, 2023: BrainTTA presentation in IEEE ICCD 2023

Our Dutch colleague Maarten Molendijk from TU Eindhoven presented a co-authored paper "BrainTTA: A 28.6 TOPS/W Compiler Programmable Transport-Triggered NN SoC" in IEEE ICCD 2023. The publication was a result of successful collaboration work between our CPC group and PARSE/TUE where a programmable TTA/SIMD-based accelerator was designed for ultra low power AI inference on low precision use cases. The design was done using the OpenASIP tools with the design work conducted by Molendijk et al. Read more about it in the preprint. The presentation slides are available here.

November 6th, 2023: New publications added
  • Topi Leppänen, Joonas Multanen, Leevi Leppänen, Pekka Jääskeläinen:
    AFOCL: Portable OpenCL Programming of FPGAs via Automated Built-in Kernel Management
    in IEEE Nordic Circuits and Systems Conference (NorCAS 2023) (download).
  • Niklas Rother, Leonard Mätzner, Pekka Jääskeläinen, Topi Leppänen, Jens Karsten Schleusner, Holger Christoph Blume:
    Synthetic Aperture Radar Algorithms on Transport Triggered Architecture Processors using OpenCL
    International Radar Conference 2023
  • Maarten Molendijk, Floran de Putter, Manil Dev Gomony, Pekka Jääskeläinen and Henk Corporaal:
    BrainTTA: A 28.6 TOPS/W Compiler Programmable Transport-Triggered NN SoC
    IEEE International Conference on Computer Design (ICCD 2023)
  • Panagiotis Mousouliotis, Topi Leppanen, Pekka Jaaskelainen, Nikos Petrellis, Panagiotis Christakos, Georgios Keramidas, Christos Antonopoulos, Nikolaos Voros:
    On the OpenCL Support for Streaming Fixed-Function Accelerators on Embedded SoC FPGAs
    The 19th International Symposium on Applied Reconfigurable Computing (ARC 2023)
November 1st, 2023: AFOCL presentation in NorCAS 2023 conference

Our doctoral researcher Topi Leppänen presented the paper "AFOCL: Portable OpenCL Programming of FPGAs via Automated Built-in Kernel Management" in NorCAS 2023. AFOCL allows FPGA device users to avoid vendor lock-in and separates the roles of software and FPGA engineer. Behind the curtain, the OpenCL implementation automatically selects IPs from a precompiled bitstream database and handles FPGA reconfiguration. Details in the paper.

August 24th, 2023: Final demonstrator video for the CPSoSAware EU project available

Check out the video below of the final demonstrator for the CPSoSAware EU project. The work was a collaboration with the University of Peloponnese. The demonstrator features a nanodrone, which offloads processing to edge resources wirelessly using Pocl-R.

August 8th, 2023: Added a publication from 2022 missing from the web page
  • Topi Leppänen, Atro Lotvonen, Pekka Jääskeläinen:
    "Cross-vendor programming abstraction for diverse heterogeneous platforms"
    in Frontiers in Computer Science, Vol. 4, Oct. 2022 (download).
June 15th, 2023: Two new publications added
  • Topi Leppänen, Atro Lotvonen, Panagiotis Mousouliotis, Joonas Multanen, Georgios Keramidas, Pekka Jääskeläinen:
    "Efficient OpenCL system integration of non-blocking FPGA accelerators"
    in Microprocessors and Microsystems (MICPRO), Vol. 97, Mar. 2023 (download).
  • Alex Hirvonen, Topi Leppänen, Kari Hepola, Joonas Multanen, Joost Hoozemans, Pekka Jääskeläinen:
    "AEX: Automated High-Level Synthesis of Compiler Programmable Co-processors"
    in Journal of Signal Processing Systems (JSPS), Feb. 2023​ (download).
October 17th, 2022: A master's thesis and a new publication added
  • Kari Hepola:
    Generation of Customized RISC-V Implementations
    (2022) (link)
  • Kanishkan Vadivel, Barry de Bruin, Pekka Jääskeläinen, Roel Jordans and Henk Corporaal:
    "Prebypass: Software Register File Bypassing for Reduced Interconnection Architecture"
    in Euromicro Conference on Digital Systems Design (DSD 2022) (download).
September 22nd, 2022: New publications added
  • Jakub Žádník, Markku Mäkitalo, Pekka Jääskeläinen,
    "Pruned Lightweight Encoders for Computer Vision"
    IEEE 24th International Workshop on Multimedia Signal Processing (MMSP 2022) download poster
  • Kari Hepola, Joonas Multanen and Pekka Jääskeläinen:
    "Dual-IS: Instruction Set Modality for Efficient Instruction Level Parallelism"
    in 35th GI/ITG International Conference on Architecture of Computing Systems (ARCS 2022) (download).
  • Kari Hepola, Joonas Multanen and Pekka Jääskeläinen:
    "OpenASIP 2.0: Co-Design Toolset for RISC-V Application-Specific Instruction-Set Processors"
    in 33rd IEEE International Conference on Applicationspecific Systems, Architectures and Processors (ASAP 2022) (download).

(older news here)

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