General articles on technical subjects.
AFDS was full of talks on OpenCL. You missed them, just like me? Then you will be happy that they put many videos on Youtube!
Enjoy watching! As all videos are around 40 minutes, it is best to take a full day for watching them all. The first part is on openCL itself, second is on tools, third on OpenCL usages, fourth on other subjects.
On 15 November 2011 Altera announced support for OpenCL. The time between announcements for having/getting OpenCL-support and getting to see actually working SDKs takes always longer than expected, so to get this working on FPGAs I did not expect anything before 2013. Good news: the drivers are actually working (if you can trust the demos at presentations).
There have been three presentations lately:
In this article I share with you what you should not have missed on these sheets, and add some personal notes to it.
Is OpenCL the key that finally makes FPGAs not tomorrow’s but today’s technology?
Thursday 4 October I talk on mobile compute at Hackers&Founders Amsterdam on what mobile compute can do. The goal is to initiate new ideas for start-ups, as not many know their mobile phone and tablet is very powerful and next year can be used for compute intensive tasks.
The other talk is from Mozilla on Firefox OS (Edit: it was cancelled), which is actually reason enough to visit this Hackers&Founders Meetup. Entrance is free, drinks are not. Alternatively you could go to the Hadoop User Group Meetup at Science Park, Amsterdam.
Let’s approach the concept of programming through looking at the brain, the code and the computer.
The idea of a program lives in the brain of a programmer. The way to get the program to the computer is using a system process called coding. When the program coded on the computer and the program embedded as an idea in the brain are alike, the programmer is happy. When over time the difference between the brain-version and the computer-version grows, then we go for a maintenance phase (although this is still this mostly from brain to computer).
When the coding-language or important coding-paradigms change, something completely different happens. In such case the program in the brain is updated or altered. Humans are not good at that, or at least not many textbooks discuss how to change from one model to another.
In this article I want to discuss one of these new coding-paradigm: dependencies in parallel software.
Continue reading “Avoiding false dependencies in only two steps”
This is a message to GPU-programmers only.
It is a simple question, and has many answers: what are GPU-brains? How is it possible your brain can code GPUs and only few friends and colleagues understand what you are doing? Is it thinking in parallel, focusing on one kernel and having the architecture in the back of the head. Is it simple loop-unrolling? Is it a web of thoughts? Is it just cool, as not many people can do it?
Recently AMD announced their new FirePro GPUs to be used in servers: the S9000 (shown at the right) and the S7000. They use passive cooling, as server-racks are actively cooled already. AMD partners for servers will have products ready Q1 2013 or even before. SuperMicro, Dell and HP will probably be one of the first.
What does this mean? We finally get a very good alternative to TESLA: servers with probably 2 (1U) or 4+ (3U) FirePro GPUs giving 6.46 to up to 12.92 TFLOPS or more theoretical extra performance on top of the available CPU. At StreamHPC we are happy with that, as AMD is a strong OpenCL-supporter and FirePro GPUs give much more performance than TESLAs. It also outperforms the unreleased Intel Xeon Phi in single precision and is close in double precision.
A multi-GPU card has various advantages as it uses less power and space, but does not compare to a single GPU. As the communication goes via the PCI-bus still, the compute-capabilities between two GPU cards and a multi-GPU card is not that different. Compute-problems are most times memory-bound and that is an important factor that GPUs outperform CPUs, as they have a very high memory bandwidth. Therefore I put a lot of weight on memory and cache available per GPU and core.
If you are looking for the samples in one zip-file, scroll down. The removed OpenCL-PDFs are also available for download.
This sentence “NVIDIA’s Industry-Leading Support For OpenCL” was proudly used on NVIDIA’s OpenCL page last year. It seems that NVIDIA saw a great future for OpenCL on their GPUs. But when CUDA began borrowing the idea of using LLVM for compiling kernels, NVIDIA’s support for OpenCL slowly started to fade instead. Since with LLVM CUDA-kernels can be loaded in OpenCL and vice versa, this could have brought the two techniques more together.
What is the cause for this decreased support for OpenCL? Did they suddenly got aware LLVM would decrease any advantage of CUDA over OpenCL and therefore decreased support for OpenCL? Or did they decide so long ago, as their last OpenCL-conformant product on Windows is from July 2010? We cannot be sure, but we do know NVIDIA does not have an official statement on the matter.
The latest action demonstrating NVIDIA’s reduced support of OpenCL is the absence of the samples in their GPGPU-SDK. NVIDIA removed them without notice or clear statement on their position on OpenCL. Therefore we decided to start a petition to get these OpenCL samples back. The only official statement on the removal of the samples was on LinkedIn:
All of our OpenCL code samples are available at http://developer.nvidia.com/opencl, and the latest versions all work on the new Kepler GPUs.
They are released as a separate download because developers using OpenCL don’t need the rest of the CUDA Toolkit, which is getting to be quite large.
Sorry if this caused any alarm, we’re just trying to make life a little easier for OpenCL developers.Best regards,
Will.
William Ramey
Sr. Product Manager, GPU Computing
NVIDIA Corporation
Continue reading “NVIDIA ended their support for OpenCL in 2012”
For yearly power-usage there is a rule-of-thumb which states that a device that is continuously on, costs the amount of Watt times 1.5 in Euro per year. So the computer in front of me, that takes around 107 Watt, costs me €160 a year if I would leave it on. A moderate cluster with several GPUs of a few hundred Watts each, would cost a few thousand Euros a year. I would say: very doable for most companies.
So why is the performance per Watt? There is more to a Watt than just the costs. The energy to cool a cluster is quite high, as most of the energy escapes via heat. And then there is the increase in demand for portable power. In cases you are thinking of sweeping you credit card for a top 10 supercomputer, then these energy-costs are extremely high.
In this article I try to get an overview of who is entering the 20+ GFLOPS/Watt area. All processors that do less than 20 GFLOPS/Watt, need to have other advantages to survive. And you’ll see that all the green processors are programmed with OpenCL, the technology StreamHPC is all about.
IMPORTANT: The total power used is sometimes including and sometimes excluding memory-transfers. So the comparison below IS NOT FAIR. The graphics cards are including memory-transfers, while the CPUs and SoCs are not.
Big Data in the previous century was the archive full of ring-binders/folders/ordners, which would grow each year at the same pace. Now the definition is that it should grow each year as much as all years before combined.
A few months ago SunGard named 10 Big Data trends transforming financial services. I have used their list as a base to have my own focus: on increased computation-demands and not specific for this one market. This resulted in 7 general trends where Big Data meets/needs OpenCL.
Since the start of StreamHPC we sought customers who could no compute through their whole data in time. Back then Big Data was still a buzz word catching on, but it best describes this one core businesses.
Look at the computers and laptops sold at your local computer shop. There are just few systems with a separate GPU, neither as PCI-device nor integrated on the motherboard. The graphics are handled by the CPU now. The Central Processing Unit as we knew it is dying.
To be clear I will refer to an old CPU as “GPU-less CPU”, and name the new CPU (with GPU included) as plain “CPU” or “hybrid Processor”. There are many names for the new CPU with all their own history, which I will discuss in this article.
The focus is on X86. The follow-up article is on whether the king X86 will be replaced by king ARM.
Know that all is based on my own observations; please comment if you have nice information.
This article is still work-in-progress
Intel has just released its OpenCL bit CPU-drivers, version 2013 bèta. It has support for OpenCL 1.1 (not 1.2 as for the CPU) on Intel HD Graphics 4000/2500 of the 3rd generation Core processors (Windows only). The release notes mention support for Windows 7 and 8, but the download-site only mentions windows 8. Support under Linux is limited to 64 bits.
The release notes mention:
cl_khr_int64_base_atomics and cl_khr_int64_extended_atomicscl_khr_fp16cl_khr_gl_sharingcl_khr_gl_eventcl_khr_d3d10_sharingcl_khr_dx9_media_sharingcl_khr_d3d11_sharing.Check the release notes for full information.
The drivers can be found on http://software.intel.com/en-us/articles/vcsource-tools-opencl-sdk-2013/. Installation is simple. For Windows there is a installer. If you have Linux, make sure you remove any previous version of Intel’s openCL drivers. If you have a Debian-based Linux, use the command ‘alien’ to convert the rpm to deb, and make sure ‘libnuma1‘ is installed. There are requirements for libc 2.11 or 2.12 – more information on that later as Ubuntu 12.04 has libc6 2.15.
Continue reading “Intel OpenCL CPU-drivers 2013 beta with OpenCL 1.2 support”
OpenCL is getting more and more important and for more developers a skill worth having. At StreamHPC we saw this coming in 2010 and have been training people in OpenCL since. A few weeks ago I got a question on how to take on OpenCL, which could be interesting for more people: how to take on OpenCL. In other words: the steps to take to learn OpenCL the quickest. Since the last time I wrote on learning OpenCL is almost two years ago, it is a good time to share more recent insights on this matter.
You see that is a whole difference from learning for instance Java with a Pascal-background. Learning VHDL for programming FPGAs comes closer, though you don’t need to tinker with timings when doing OpenCL. Let’s go through the steps.
Programmers know the value of everything and the costs of nothing. I saw this quote a while back and loved it immediately. The quote by Alan Perlis is originally about Perl LISP-programmers, but only highly trained HPC-programmers seem to have obtained this basic knowledge well. In an interview with Andrew Richards of Codeplay I heard it from another perspective: software languages were not developed in a time that cache was 100 times faster than memory. He claimed that it should be exposed to the programmer what is expensive and what isn’t. I agreed again and hence this post.
I think it is very clear that programming languages (and/or IDEs) need to be redesigned to overcome the hardware-changes of the past 5 years. I talked about that in the article “Separation of compute, control and transfer” and “Lots of loops“. But it does not seem to be enough.
So what are the costs of each operation (on CPUs)?
This article is just to help you on your way, and most of all: to make you aware. Note it is incomplete and probably not valid for all kinds of CPUs.
Just a quick teaser. More materials (photos, sheets, videos) are coming soon.
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Music by Professor Kliq.
Below is the short version with photos only
More than two years ago, on 13 January 2010, I wrote my first blog-post. Four months later StreamComputing (redacted: rebranded to StreamHPC in 2017) was both official and unknown. I want to share with you my personal story on how I got to start-up this company.
I wanted to create a company which was about innovative projects – something I had hardly encountered until then. The years before I programmed parts of A-to-B-flows, as I call them. That is software that is in the base quite simple, but tediously discussed as very, very complex.
The complexity is not the software, as you can see. It is undocumented APIs, forgotten knowledge, knowledge in heads of unknown people, bossy and demanding people who friendly ask for last-minute architecture changes, deadlines around promotion-rounds, new deadlines due to board-decisions, people being afraid of getting replaced if the software is finished, jealousy if another team makes version 2 of the software, etc. The rule of office-software is therefore understandable:
Software is either unfinished, or turned into a platform for unintended functionality.
The fun in office-software is there for analyst, architect or manager – the developer just puts in his earphones and makes all the requested changes (hooray for services like Spotify). But as I did not want to become a manager and wished to keep improving my development skills, I had to conclude I was on the wrong track.
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/.
If you want to see what is coming up in the market of consumer-technology (PC, mobile and tablet), then NVIDIA can tell you the most. The company is very flexible, and shows time after time it really knows in which markets is currently operates and can enter. I sometimes strongly disagree with their marketing, but watch them closely as they are in the most important markets to define the near future in: PCs, Mobile/Tablet and HPC.
The Khronos Group gave some talks on their technologies in Shanghai China on the 17th of March 2012. Neil Trevett did some interesting remarks on the position of NVidia on OpenCL I would like to share with you. Neil Trevett is both an important member of Khronos and employee of NVidia. To be more precise, he is the Vice President Mobile Content of NVidia and the president of Khronos. I think we can take his comments serious, but we must be very careful as these are mixed with his personal opinions.
Regular readers of the blog have seen I am not enthusiastic at all about NVidia’s marketing, but am a big fan of their hardware. And exactly I am very positive they are bold enough in the industry to position themselves very well with the fast-changing markets of the upcoming years. Having said that, let’s go to the quotes.
All quotes were from this video. Best you can do is to start at 41:50 till 45:35.
At 44:05 he states: “In the mobile I think space CUDA is unlikely to be widely adopted“, and explains: “A party API in the mobile industry doesn’t really meet market needs“. Then continues with his vision on OpenCL: “I think OpenCL in the mobile is going to be fundamental to bring parallel computation to mobile devices” and then “and into the web through WebCL“.
Also interesting at 44:55: “In the end NVidia doesn’t really mind which API is used, CUDA or OpenCL. As long as you are get to use great GPUs“. He ends with a smile, as “great GPUs” refers to NVidia’s of course. 🙂
At 45:10 he puts NVidia’s plans on HPC, before getting back to : “NVidia is going to support both [CUDA and OpenCL] in HPC. In Mobile it’s going to be all OpenCL“.
At 45:23 he repeats his statements: “In the mobile space I expect OpenCL to be the primary tool“.
Now that smartphones get more powerful and internet makes it possible to have all functionality and documents with you anywhere, the computer needs to be reinvented. You see all big IT-companies searching for how that can be, from Windows Metro to complete docking stations to replace the desktop by your phone. A turbulent market.
One of the new products are USB-stick sized computers. Stick them into a TV or monitor, zap in your code and you have your personal working environment. You never need to carry laptops to your hotel-room or conference, as long as a screen is available – any screen.
There are several USB-computers entering the market, but I wanted to introduce you to two. Both of these see a future in a strong processor in a portable device, and both do not have a real product with these strong processors. But you can expect that in 2013 you can have a device that can do very fast parallel processing to have a smooth Photoshop experience… at your key-ring.
By exception, another PDF-Monday.
OpenCL vs. OpenMP: A Programmability Debate. The one moment OpenCL and the other mom ent OpenMP produces faster code. From the conclusion: “OpenMP is more productive, while OpenCL is portable for a larger class of devices. Performance-wise, we have found a large variety of ratios between the two solutions, depending on the application, dataset sizes, compilers, and architectures.”
Improving Performance of OpenCL on CPUs. Focusing on how to optimise OpenCL. From the abstract: “First, we present a static analysis and an accompanying optimization to exclude code regions from control-flow to data-flow conversion, which is the commonly used technique to leverage vector instruction sets. Second, we present a novel technique to implement barrier synchronization.”
Variants of Mersenne Twister Suitable for Graphic Processors. Source-code at http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MTGP/
Accelerating the FFTD method using SSE and GPUs. “The Finite-Difference Time-Domain (FDTD) method is a computational technique for modelling the behaviour of electromagnetic waves in 3D space”. This is a project-plan, but describes the theories pretty well. Continue reading “PDFs of Monday 16 April”
In “Separation of compute, control and transfer” I talked about node-wise programming as a method we should embrace instead of trying to unroll the existing loops. In this article I get into loops and discuss a few types and how they can be run in a parallel form. Dependency is the big variable in each type: the lower the dependency on previous iterations, the better it can be parallelised. Another one is the known iteration-dimensions known before the loop is started.
The more you think about it, the more you find that a loop is not a loop.
