The printf-funtion in kernels isn’t the solution to everything, so hence profilers and debuggers specially tailored for GPU-programming. On Windows there is a lot of choice, but mostly only if you have a paid version of Visual Studio. On Linux you have GDB, but that program is not really user-friendly for the GUI-lovers.

For AMD there is now gDEBugger again available for Linux. Again, as version 5.8 by Gremedy worked with Linux, after AMD bought the company it got Windows-only for version 6. A few weeks ago, 10 months after 6.0, Linux-binaries got back with version 6.2. It supports OpenCL 1.2, OpenGL 3.2 and quite some extensions. As only AMD is supported, later more on debugging OpenCL-applications on NVidia and Intel.

Installation is quite straightforward. For creating a menu-item, you’ll find an useful image in /opt/gDEBugger6.2.xxx/tutorial/images/.

Continue reading “AMD gDEBugger 6.2 for Linux” →

This year we’re unfortunately not at SuperComputing 2015 for reasons you will hear later. But we haven’t forgotten about the people going and trying to find a share of OpenCL. Below is a list of companies having a booth at SC15, which was assembled by the guys of IWOCL and we completed with some more background information.

Khronos

The first place to go to is booth #285 and meet Khronos to hear where to go at SC15 to see how OpenCL has risen over the years. More info here. Say hi from the StreamHPC team!

OpenCL on FPGAs

Altera | Booth: #462. Expected to have many demos on OpenCL. See their program here. They have brought several partners around the floor, all expecting to have OpenCL demos:

• Reflex | Booth: #3115.
• BittWare | Booth #3010.
• Nallatech | Booth #1639.
• Gidel | Booth #1937.

Xilinx | Booth: #381. Expected to show their latest advancements on OpenCL. See their program here.

Microsoft | Booth: #1319. Microsoft Bing is accelerated using Altera and OpenCL. Ask them for some great technical details.

ICHEC | Booth #2822. The Irish HPC centre works together with Xilinx using OpenCL.

Embedded OpenCL

ARM | Booth: #2015. Big on 64 bit processors with several partners on the floor. Interesting to ask them about the OpenCL-driver for the CPU and their latest MALI performance.

Huawei Enterprise | #173. Recently proudly showed the world their OpenCL capable camera-phones, using ARM MALI.

HPC OpenCL

Below are the three companies that promise at least 1 TFLOPS DP per co-processor.

Intel | Booth: #1333/1533. Where they spoke about OpenMP and forgot about OpenCL, Altera has brought them back. Maybe they share some plans about Xeon+FPGA, or OpenCL support for the new XeonPhi.

AMD | Booth: #727. HBM, HSA, Green500, HPC APU, 32GB GPUs and 2.2 TFLOPS performance – enough to talk about with them. Also lots of OpenCL love.

NVidia | Booth: #1021. Every year they have been quite funny when asked about why OpenCL is badly supported. Please do ask them this question again! Funniest answer wins something from us – to be decided.

Others

You’ll find OpenCL in many other places.

ArrayFire | Booth #2229. Their library has an OpenCL backend.

IBM | Booth: #522. Now Altera joined Intel, IBM’s OpenPower has been left with NVidia for accelerators. OpenCL could revive the initiative.

NEC | Booth: #313. The NEC group has accelerated PostgreSQL with OpenCL.

Send your photos and news!

Help us complete this post with news and photos, to complete this post. We’re sorry not to be there this year, so we need your help to make the OpenCL party complete. You can send via email, twitter and in the comments below. Thanks in advance!

An overview of all the tutorials and talks for easy reading.

You can also download the PDF.

Heterogeneous Computing Using Modern C++ with OpenCL Devices – Rod Burns and Ruyman Reyes (Codeplay)

This hands-on session will provide an opportunity to get experience with SYCL using ComputeCpp™ Community Edition, a free to use implementation of the SYCL 1.2 standard. Attendees will be shown how to set up ComputeCpp and use it to write their own SYCL code to run on supported GPUs and CPUs.

SYCL is already able to dispatch to heterogeneous devices and it implements C++17 ParallelSTL, augmenting it with ability to dispatch to GPUs in addition to CPUs. This tutorial will demonstrate how to write parallel SYCL code and how to use the Khronos Group’s experimental Parallel STL implementation. The course outline is as follows

• Start with a basic SYCL program that shows how to submit queues in a single task and stream-like object, comparing CPU, SYCL and OpenCL versions
• Demonstrate how to access data across host and GPUs using buffers and accessors, the importance of life-time, and basic parallel constructs

Attendees are expected to have programming experience with C++ and a laptop either running Linux or having a VM manager installed such as VirtualBox. The required software will be provided on USB-sticks. This course is suitable for beginners, but is focused on intermediate to advanced parallel programming using C++.

Harnessing the Power of FPGAs with the Intel FPGA SDK for OpenCL- Byron Sinclair, Andrew Ling and Genady Paikin (Intel)

In this tutorial, we will introduce you to the reconfigurable hardware architecture and programming of Field Programmable Gate Arrays (FPGAs).

You will learn why FPGAs have become so popular in recent years, and understand the many advantages of using FPGAs in your HPC application. In particular, we will cover architectural features of FPGAs that make them well suited to many complex operations, including matrix multiplications and convolutions. In addition, we will introduce you to programming FPGAs using the Intel® FPGA SDK for OpenCL, and how specific OpenCL coding techniques can lead to efficient circuits implemented on the FPGA.

Finally, we will go over several case studies where FPGAs have shown very competitive performance when programmed using OpenCL, including convolutional neural nets, FFTs, and astronomy de-dispersion algorithms.

Unlock Intel GPUs for High Performance Compute, Media and Computer Vision Capabilities with Intel OpenCL Extensions – Jeff Mcallister, Biju George, Adam Herr and Ben Ashbaugh (Intel)

The keys to unlock the full performance potential of Intel GPUs for emerging workloads in general compute, media, computer vision, and machine learning are in the rich suite of Intel OpenCL extensions. These give developers direct access to unique Intel hardware capabilities, which until now have been difficult to master.
This tutorial builds step by step with multiple examples, including:

• How to write high performance general compute applications based on the core concept of OpenCL subgroups.
• How to use additional subgroup operations described in the Intel subgroups and media block read/write extensions.
• Then using the framework of subgroups, we explain the device-side motion estimation extension which leverages the unique Intel GPU media sampler to accelerate motion estimation operations from OpenCL kernels.
• Finally we explain the Video Enhancement (VEBOX) extension, which is an OpenCL host level API extension to leverage a powerful media fixed function unit to accelerate many frame level video enchancement operations.

Faster, smarter computer vision with AI and OpenCL – Uri Levy and Jeffrey Mcallister (Intel)

Learn how to use Intel machine learning and computer vision tools to get from concept to market faster for machine learning applications based on OpenCL and OpenVX. Build two example scenarios: autonomous driving with FPGA inference and a smart camera app using Intel Graphics inference. This presentation will show how a unified set of tools can reduce the complexity of developing heterogeneous machine learning apps – from training a model with input images, to creating a custom classifier, to building an optimized traditional computer vision pipeline around the classifier to create a full computer vision application

GPGPU Acceleration using OpenCL for a Spotlight SAR Simulator – Eric Balster, Jon Skeans and David Fan (University of Dayton) Marc Hoffman (US Air Force Research Laboratory)

In this paper, OpenCL is used to target a general purpose graphics processing unit (GPGPU) for acceleration of 2 modules used in a synthetic aperture radar (SAR) simulator. Two of the most computationally complex modules, the Generate Return and Back Projection modules, are targeted to an AMD FirePro M5100 GPGPU. The resulting speedup is 2.5X over multi-threaded C++ implementations of those algorithms running on an 8-core Intel I7 2.8GHz processor, 5X over singlethreaded C++ implementations, and 24X over native MATLAB implementations, on average.

Near Real-Time Risk Simulation of Complex Portfolios on Heterogeneous Computing Systems with OpenCL – Javier Alejandro Varela and Norbert Wehn (University of Kaiserslautern)

In this work, we exploit OpenCL to efficiently map the nested simulation of complex portfolios with multiple algorithms on heterogeneous computing systems. Code portability and customizations allow us to profile the kernels on different accelerating platforms, such as CPU, Intel’s Xeon Phi and GPU. The combination of OpenCL, a new bit-accurate algorithmic optimization and the extension of an existing numerical interpolation scheme allows us to achieve 1000x speedup compared to the state-of-the-art approach. Our system design minimizes costly host-device transfers and global memory, enabling complex portfolios to be easily scaled.

A Performance and Energy Evaluation of OpenCL-accelerated Molecular Docking – Leonardo Solis Vasquez and Andreas Koch (Technische Universität Darmstadt)

This work presents an OpenCL implementation of AutoDock, and a corresponding performance evaluation on two different platforms based on multi-core CPU and GPU accelerators. It shows that OpenCL allows highly efficient docking simulations, achieving speedups of ∼4x and ∼56x over the original serial AutoDock version, as well as energy efficiency gains of ∼2x and ∼6x. respectively. To the best of our knowledge, this work is the first one also considering the energy efficiency of molecular docking programs.

Assessing the feasibility of OpenCL CPU implementations for agent-based simulations – Nuno Fachada and Agostinho Rosa (Instituto Superior Técnico, Portugal)

In this paper we evaluate the feasibility of using CPU-oriented OpenCL for high-performance simulations of agent-based models. We compare a CPU-oriented OpenCL implementation of a reference ABM against a parallel Java version of the same model. We show that there are considerable gains in using CPU-based OpenCL for developing and implementing ABMs, with speedups up to 10x over the parallel Java version on a 10-core hyper-threaded CPU.

Enabling FPGAs as a True Device in the OpenCL Standard – Vincent Mirian and Paul Chow (University Of Toronto)

As FPGA capacities continue to increase, the ability to partition and partially reconfigure the FPGA will become even more desirable. The fundamental issue is how FPGAs are currently viewed as devices in the OpenCL model. In this paper, we propose a small change to the OpenCL definition of a device that unlocks the full potential of FPGAs to the programmer.

Applying Models of Computation to OpenCL Pipes for FPGA Computing – Nachiket Kapre and Hiren Patel (University of Waterloo)

We propose imposing a communication discipline inspired from models of computation (e.g.Ptolemy) such as SDF (synchronous dataflow), bulk synchronous (BSP), or Discrete Event (DE). These models offer a restricted subset of communication patterns that enable implementation tradeoffs and deliver performance and resource guarantees. This is useful for OpenCL developers operating within the constraints of the FPGA device. We hope to facilitate a preliminary analysis and evaluation of supporting these patterns in OpenCL and quantifying associated FPGA implementation costs.

Accelerating Applications at Cloud Scale using FPGAs – Sarah Siripoke, Fernando Martinez Vallina and Spenser Gilliland (Xilinx)

The acceptance and success of cloud computing has given application developers access to computing and new customers at a scale never seen below. The inherent ability of an FPGA to reconfigure and be workload optimized is a great advantage given the fast-moving needs of cloud computing applications. In this talk we will discuss how users can develop, accelerate and deploy accelerated applications in the cloud at scale. You will learn how to get started on a turn-key OpenCL development environment in the cloud using Xilinx FPGAs.

Creating High Performance Applications with Intel’s FPGA OpenCL SDK – Andrew Ling, Utku Aydonat, Davor Capalija, Shane O’Connell and Gordon Chiu (Intel)

After decades of research, High-Level Synthesis has finally caught on as a mainstream design technique for FPGAs. However, achieving performance results that are comparable to designing at a hardware description level still remains a challenge. In this talk, we illustrate how we achieve world class performance results on HPC applications by using OpenCL. Specifically, we show how we achieve 1Tflop of performance on a matrix multiply and over 1.3Tflops on a CNN application, run on Intel’s 20nm Arria 10 FPGA device. Finally, we will describe spatial coding techniques that lead to efficient structures, such as systolic-arrays, to ensure that the FPGA runs efficiently.

Symphony – Task Scheduling and Memory Management in Heterogeneous Computing – Amit Jindal and Wenjia Ruan (Qualcomm Technologies)

Task scheduling and memory management are challenges that make Heterogeneous Computing difficult for the masses. There are several programming models and tools that exist targeting partitioning of workload and accessibility of data between CPU and GPU. We have developed and deployed Symphony SDK – a framework that makes workload partitioning, scheduling and memory management ‘simple’ for developers. In this talk, we will introduce Symphony architecture, elaborate how existing OpenCL kernels can be reused with heterogeneous task synchronization, task scheduling, and memory management capabilities of Symphony. We will also share real-world cases where Symphony has provided 2x-6x performance speed-ups.

CUDA-on-CL: A compiler and runtime for running modern CUDA c++11 applications on OpenCL 1.2 devices – Hugh Perkins (ASAPP)

Cuda-on-cl addresses the problem of creating and maintaining OpenCL forks by leaving the reference implementation entirely in NVIDIA CUDA, and writing both a compiler and a runtime component, so that any CUDA c++11 application can in theory be compiled and run directly on any OpenCL 1.2 device. We use Tensorflow framework as a case-study, and demonstrate the ability to run Tensorflow and Eigen kernels directly, with no modification to the original CUDA source-code. Performance studies are also undertaken, and show that the cuda-on-cl program runs at about 25% of the original CUDA-compiled version.

OpenCL in Scientific High Performance Computing—The Good, the Bad, and the Ugly – Matthias Noack (Zuse Institute Berlin)

We present experiences with utilising OpenCL alongside C ++ , MPI, and CMake in two real-world scientific codes. Our targets are a Cray XC40 supercomputer with multi- and many-core (Xeon Phi) CPUs, as well as multiple smaller systems with Nvidia and AMD GPUs. We shed light on practical issues arising in such a scenario, like the interaction between OpenCL and MPI, discuss solutions, and point out current limitations of OpenCL in the domain of scientific HPC from an application developer’s and user’s point of view.

Accelerated Machine Learning Using TensorFlow and SYCL on OpenCL Devices – Andrew Richards, Mehdi Goli and Luke Iwanski (Codeplay)

Codeplay has been working with Google to add SYCL back-end support in TensorFlow, one of the most popular machine learning frameworks, enabling developers to use OpenCL devices with their machine learning applications. SYCL provides an abstraction layer that simplifies parallel development, giving developers access to the computing power of OpenCL devices and reducing the amount of code required. Andrew Richards will talk about how machine learning applications can harness the power of OpenCL using open standards and how, by using SYCL, TensorFlow can be extended to include customized operations running on OpenCL devices.

Analyzing and improving performance portability of OpenCL applications via auto-tuning – James Price and Simon McIntosh-Smith (University of Bristol)

In this talk, we present an approach for analyzing performance portability that exploits that black-box nature of automatic performance tuning techniques. We demonstrate this approach across a diverse range of GPU and CPU architectures for two simple OpenCL applications. We then discuss the potential for auto-tuning to aid the generation of performance portable OpenCL kernels by incorporating multi-objective optimization techniques into the tuning process.

Wavefront Parallel Processing on GPUs with an Application to Video Encoding Algorithms – Biju George and Ben Ashbaugh (Intel)

In this presentation we focus on the application of the wavefront pattern to design efficient GPGPU implementations of video encoding algorithms using OpenCL kernels. We present our experiences in implementing and evaluating four solutions of WPP for inter and intra estimation for AVC on GPUs. We explain the reasoning behind each solution and present the results of our analysis.

Challenges and Opportunities in Native GPU Debugging with OpenCL – Uri Levy (Intel)

In this technical session we’ll present the open architectural design of the debugger and how it fits into the OpenCL JIT compilation flow and the underlying compute technology of the HW with focus on Intel processor graphics. We’ll demonstrate a show case on how to natively work with the debugger to solve functional bugs, as-well-as low-level debugging techniques on SIMD thread level which help to solve complex issues such as misaligned or out of range accesses to local\global memory, stack overflows, Illegal instructions, etc. Finally, we’ll cover the challenges in debugging

Modeling Explicit SIMD Programming with Subgroup Functions – Biju George and Ben Ashbaugh (Intel)

In this presentation, based on our experience in developing publicly released vendor extensions based on subgroups, we explain the advantages of the “explicit SIMD” programming paradigm using OpenCL subgroup and how the subgroups framework can be leveraged to: (1) Model features for performance in OpenCL that are commonly available in programming languages or interfaces based on an “explicit SIMD” programming paradigm such as the AVX intrinsics supported in GCC; and to (2) Model features to expose functionality available in GPU accelerator units that are more conveniently and efficiently exposed using a block API.

What do you do when you want to explain OpenCL and FPGAs and OpenCL-on-FPGAs to a beer drinking crowd in just 15 minutes? Well, you simply can’t go deep into the matter. On a Thursday evening, 5 November 2015,  I was standing on a chair for a beer-loving group of Hackers and Founders with my laser-powered presenter, trying not to loose everybody. It was not the first time I stood on that particular chair – some years ago I presented about OpenCL-on-GPUs.

Below you find the full presentation – feel free to use and change the slides for yourself (PDF here).

Do you want us to present OpenCL, accelerators or performance engineering in a talk tailored for your audience? Just give us a call.

Important: this is only for Google-branded Nexus phones – other brands are free to do what they want, and they most-probably will.

Also important: this doesn’t mean that OpenCL on Android devices will be over, but that there is a bump in the road now Google tries to lock-in customers to their own APIs.

The big idea behind OpenCL is that higher level languages and libraries can be built on top of it. This is exactly what was done under Android: RenderScript Compute (a higher-level language)  was implemented using OpenCL for ARM Mali GPUs.

Having OpenCL drivers on Android has several advantages, such that OpenCL can directly be used on Android and that there is room for other high-level languages that have OpenCL as back-end. Especially the latter is what probably made Google decide to cripple the OpenCL-drivers.

Google seems to be afraid of competition, and that’s a shame, as competition is the key factor that drives innovation. The OpenCL community is not the only one complaining about Google’s intentions concerning Android. Read page 3 of that article to understand how Google is controlling handset-vendors and chip-makers.

Google’s statement

In February OpenCL drivers were discovered on two Nexus tablets using a MALI T604 GPU. Around the same time there was one public answer from Google employee Tim Murray (twitter) why Google did not want to choose OpenCL: Continue reading “Google blocked OpenCL on Nexus with Android 4.3” →

Getting about the same code in C and OpenCL has lots of advantages, when maximum optimisations and vectors are not needed. One thing I bumped into myself was that rounding in C++ is different, and decided to implement the OpenCL-functions for rounding in C.

The OpenCL-page for rounding describes many, many functions with this line:

destType convert_destType<_sat><_roundingMode>(sourceType)

So for each sourceType-destType combination there is a set of functions: 4 rounding modes and an optional saturation. Easy in Ruby to define each of the functions, but takes a lot more time in C.

The 4 rounding modes are:

The below pieces of code should also explain what the functions actually do.

Round to nearest even

This means that the numbers get rounded to the closest number. In case of 3.5 and 4.5, they both round to the even number 4. Thanks for Dithermaster, for pointing out my wrong assumption and clarifying how it should work.

inline int convert_int_rte (float number) {
   int sign = (int)((number > 0) - (number < 0));
   int odd = ((int)number % 2); // odd -> 1, even -> 0
   return ((int)(number-sign*(0.5f-odd)));
}

I’m sure there is a more optimal implementation. You can fix that in Github (see below).

Round to zero

This means that positive numbers are rounded up, negative numbers are rounded down. 1.6 becomes 1, -1.6 also becomes 1.

inline int convert_int_rtz (float number) {
   return ((int)(number));
}

Effectively, this just removes everything behind the point.

Round to positive infinity

1.4 becomes 2, -1.6 becomes 1.

inline int convert_int_rtp (float number) {
   return ((int)ceil(number));
}

Round to negative infinity

1.6 becomes 1, -1.4 becomes 2.

inline int convert_int_rtp (float number) {
   return ((int)floor(number));
}

Saturation

Saturation is another word for “avoiding NaN”. It makes sure that numbers are between INT_MAX and INT_MIN, and that NaN returns 0. If not used, the outcome of the function can be anything (-2147483648 in case of convert_int_rtz(NAN) on my computer). Saturation is more expensive, so therefore it’s optional.

inline float saturate_int(float number) {
  if (isnan(number)) return 0.0f; // check if the number was already NaN
  return (number>MAX_INT ? (float)MAX_INT : number

Effectively the other functions become like:

inline int convert_int__sat_rtz (float number) {
   return ((int)(saturate_int(number)));
}

Doubles, longs and getting started.

Yes, you need to make functions for all of these. But you could ofcourse also check out the project on Github (BSD licence, rudimentary first implementation).

You’re free to make a double-version of it.

According to the latest newsletter of the Mont-Blanc Project, it was explained that the GPU on a Samsung Exynos 5 is much faster and greener than its CPU: 3.5 times faster with half the energy. They built a supercomputer using 810 Exynos SoCs, that can deliver a 26 TFLOPS of peak performance. With the upcoming mobile GPUs becoming exponentially faster, they have all the expertise to build an even faster and greener ARM-supercomputer after this.

The Mont-Blanc compute cards deliver considerably higher performance; at 50% lower energy consumption, compared with previous ARM-based developer platforms.

The Mont-Blanc prototype is based on the Samsung Exynos 5 Dual SoC, which integrates a dual-core ARM Cortex-A15 and an on-chip ARM Mali-T604 GPU, and has been featured and market proven in advanced mobile devices. The dual-core ARM Cortex-A15 delivers twice the performance of the quad-core ARM Cortex-A9, used in the previous generation of ARM-based prototype, whilst consuming 20% less energy for the same workload. Furthermore, the on-chip ARM Mali-T604 GPU provides 3.5 times higher performance than the dual-core Cortex-A15, whilst consuming half the energy for the same workload.

Each Mont-Blanc compute card integrates one Samsung Exynos 5 Dual SoC, 4 GB of DDR3-1600 DRAM, a microSD slot for local storage and a 1 GbE NIC, all in an 85x56mm card (3.3×2.2 inches). A single Mont-Blanc blade integrates fifteen Mont-Blanc compute cards and a 1 GbE crossbar switch, which is connected to the rest of the system via two 10 GbE links. Nine Mont-Blanc blades fit into a standard BullX 9-blade INCA chassis. A complete Mont-Blanc rack hosts up to six such chassis, providing a total of 1620 ARM Cortex-A15 cores and 810 on-chip ARM Mali-T604 GPU accelerators, delivering 26 TFLOPS of peak performance.

“We are only scratching the surface of the Mont-Blanc potential”, says Alex Ramirez, coordinator of the Mont-Blanc project. “There is still room for improvement in our OpenCL algorithms, and for optimizations, such as executing on both the CPU and GPU simultaneously, or overlapping MPI communication with computation.”

Continue reading “ARM Mali-T604 GPU has 3.5x more performance than dual core Cortex-A15” →

If you’re into computational finance, you might have heard of FinanceBench.

It’s a benchmark developed at the University of Deleware and is aimed at those who work with financial code to see how certain code paths can be targeted for accelerators. It utilizes the original QuantLib software framework and samples to port four existing applications for quantitative finance. It contains codes for Black-Scholes, Monte-Carlo, Bonds, and Repo financial applications which can be run on the CPU and GPU.

The problem is that it has not been maintained for 5 years and there were good improvement opportunities. Even though the paper was already written, we think it can still be of good use within computational finance. As we were seeking a way to make a demo for the financial industry that is not behind an NDA, this looked like the perfect starting point for that. We have emailed all the authors of the library, but unfortunately did not get any reply. As the code is provided under an permissive license, we could luckily go forward.

The first version of the code will be released on Github early next month. Below we discuss some design choices and preliminary results.

Embedded processors always have had the focus on low-energy. Now a combination of Moore’s law, the frequency-wall and multi-processor developments have made it possible for these processors to compete in completely new market segments. Most notable due to impressive advancements in graphics IP.
We are now looking at four groups who are interested in learning from each other:

• The embedded processor market
• The FPGA market
• The HPC and server market
• The GPGPU market

And answer the question: how can we get more out of low-energy processors by looking at other industries?

The goal of the LEAP conference is to bring these three groups together. Creating the windows to each other and paving roads over the newly constructed bridges. This makes it one of its kind. Half of the conference is focused on quality information sharing and the other half on networking. For more information, check the website of the LEAP-conference. StreamHPC is a co-organiser.

Call for papers is now open! Programme is filled!

For more information on the program, contact us. For information on sponsoring, contact Tim Lewis of CroftEdge.

Website with more info and ticket-sales will open 1 February.