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Comment: Re:Lack of standards, quality. (Score 1) 158

by oneofthose (#39938903) Attached to: The Wretched State of GPU Transcoding
They are doing the match correctly. Floating point operations are commutative: a + b = b + a. But they are not assoziative: (a + b) + c != a + (b + c). This leads to different results on GPUs where algorithms are parallelized in different ways. Let's assume in your algorithm you have to calculate the inner product of a vector v = [v1, v2, v3, ..., vn]. A CPU might calculate rho = v1 + v2 + v3 + ... + vn. GPU1 might calculate in parallel: rho1 = v1 + v2, rho2 = v3 + v4, ... and finally rho = rho1 + rho2 + rhon. Depending on the GPU the way such operations are parallelized differs because the number of floaint point processors differs. So the hardware modifies the formular in a subtile way that leads to varying results. Great references for this are "Precision & Performance: Floating Point and IEEE 754 Compliance for NVIDIA GPUs" and of course "What Every Computer Scientist Should Know About Floating-Point Arithmetic".

Comment: Yevgeny Zamyatin (Score 2) 1244

by oneofthose (#39272687) Attached to: Ask Slashdot: Good, Forgotten Fantasy & Science Fiction Novels?
'We' by Yevgeny Zamyatin is an excellent dystopian book that is said to have inspired Orwell. There are incredible non english SciFi novels out there but many top 100 lists and english readers seem to be ignorant and miss out on them albeit they are definitley worth the read. Also read Stanisaw Lem, his books are hilarious ('The Futurological Congress') and philosophical ('Solaris').

Comment: 8 GPU System (Score 1) 205

by oneofthose (#38255704) Attached to: Ask Slashdot: Parallel Cluster In a Box?
I have built 4 and 8 GPU systems. For 8 GPUs the TYAN FT72B7015 is currently the only solution that I know of. Here are some product offers with this board http://blog.renderstream.com/2010/11/renderstream-announces-12-tflop-systems/ The GeForce cards are fine but since they are not built for 24/7 on HPC use, most vendors will warn you about warranty issues if something breaks in such a system. But they are cheap, just put 2 additional cards on the shelf next to the system and replace if needed. They get extremely hot, so consider how to cool such a beast in advance. The cards are also considerably faster than the Tesla solutions. If you need raw performance, ECC will slow you down so see if you can do without.

Comment: Similarly impressive Technology (Score 1) 115

by oneofthose (#37919392) Attached to: New Algorithm Could Substantially Speed Up MRI Scans

While I can not comment on the content or merit of this work since I have not read the paper I can say that there is a lot of research going on in the area of MRI and a number of exciting things are happening. I work in a research group that works on impressive MRI techniques combined with algorithms that allow taking entire MRI movies (not just photographs). This is extremely interesting when looking at the beating human heart, speaking humans or moving joints. We are really just beginning to explore the potential this technology has for clinical applications. More information including impressive videos can be found here: http://en.wikipedia.org/wiki/Real-time_MRI.

The idea behind the extremely fast acquisition times is extreme under-sampling combined with iterative algorithms that are able to produce high quality images despite the incomplete measurements. This algorithms also exploit the fact that between two frames there is not a lot of change in the images since they are taken at time intervals of only dozens of ms. They are of course more complicated than simple fourier transforms as they model the acquisition process in more detail.

Comment: Re:the best. (Score 1) 553

by oneofthose (#33901476) Attached to: Bjarne Stroustrup Reflects On 25 Years of C++
How is this not beautiful:

template<class S1, class S2> struct cartesian_product_types
{
  template<class V, class S, class State>
  struct inner
  {
    typedef typename boost::mpl::fold<S
   , State
   , boost::mpl::push_back< boost::mpl::_1
              , std::pair<V
                     ,boost::mpl::_2
                     >
              >
   >::type type;
  };

  typedef typename boost::mpl::fold<S1
   , boost::mpl::vector<>
   , inner<boost::mpl::_2, S2, boost::mpl::_1>
   >::type type;
};

But seriously, I think the language is amazing. The fact that they built a turing-complete language inside the template engine essentially by accident (thus allowing meta programming and modern C++), the fact that by now we can write simple compile time compilers (see boost proto) and the fact that you can so radically change the syntax of the language that you can basically make it look like anything you want should convince someone who spends some time with a C++ compiler and a couple of Boost libraries of this fact.

Comment: Project Suggestion: NT2 (Score 1) 283

by oneofthose (#33867550) Attached to: Grad Student Looking To Contribute To Open Source
NT2 http://github.com/jfalcou/nt2/ is an emerging numerical computation library built on top of very modern C++ libraries and ideas. It is closely related to Boost libraries.
From the description: The Numerical Template Toolbox (NT2) is an Open Source C++ library aimed at simplifying the development, debugging and optimization of high-performance computing application by providing a Matlab like syntax that ease the transition between prototype and actual application.
A way to contribute would be to make yourself familiar with it's use (e.g. port some of your Matlab scripts). Try to understand the basics of how it works internally. You will find features missing that you could try to add. Above all though, you will learn a lot.

Comment: Re:The Pirate Party probably was a one-hit wonder (Score 1) 210

by oneofthose (#33685628) Attached to: Swedes Cast Write-In Votes for SQL Injection, Donald Duck
While I agree with most of what you say in your article, there are large parts of the Pirate-Agenda missing in you analysis. One of the major topics the party concerns itself with is one of the most important questions we as a society will face in the coming years: privacy and freedom. I think these points should not be missing in any analysis of the pirate party.

Our policy is, when in doubt, do the right thing. -- Roy L. Ash, ex-president, Litton Industries

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