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There's No Such Thing As a General-Purpose Processor

gentryx We're no longer at the origin (181 comments)

Architectural improvements for general purpose CPUs yield less and less benefits: Even more registers? Even better branch prediction? Even larger caches? It'll all yield but a few percent, at least for current Intel designs. So, the way to go is currently more and more cores, but what good is it to have many cores that can't all fire simultaneously?

about a month ago
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There's No Such Thing As a General-Purpose Processor

gentryx Clickbait Caption, but Valid Arguments (181 comments)

Of course general purpose CPUs exist, simply because we call them that way. But it is also true that each design has it's own strengths, and "dark silicon" is another driver for special purpose hardware. Efficiency is another. Andrew Chien has published some interesting research on this subject. In his 10x10 approach he suggests to use 10 different types of domain-specific compute units (e.g. for n-body, graphics, tree-walking...), each of which is 10x more efficient than "general purpose CPUs" in its domain (YMMV). Those compute units bundled together, make up one core of the 10x10 design. Multiple cores can be connected via a NoC.

Let's see how software will cope with this development...

ps: can special purpose hardware exist if general purpose hardware doesn't?

about a month and a half ago
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35,000 Walrus Come Ashore In Alaska

gentryx Is the joke here... (292 comments)

...that 35k come to Point Lay to get laid?

about 3 months ago
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Japan's Shinkansen Bullet Trains Celebrate 50th Anniversary

gentryx Re:Hai! (111 comments)

One reason might be that railways are more efficient in densely populated areas. There express trains can even compete with airplanes. Yesterday we went from Tokyo to Osaka. Flight time would have been ~1h, plus 1h checkin and transfer to/from the airport (~45min. each). The Nozomi Shinkansen took us there in 2:30, and both stations were directly at the center of the cities.

Most of Japan's population is situated in coastal regions, so just a hand full of routes can service all major cities. Imagine how many connections you'd need in the US...

about 3 months ago
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Linus Torvalds: "GCC 4.9.0 Seems To Be Terminally Broken"

gentryx Need many compilers? Try Gentoo... (739 comments)

On my machine, I have clang 3.4.2-r100, gcc 4.9.0, 4.8.3, 4.7.4, 4.6.4 and icc 14.0.3.174 installed. All simultaneously, no hassle.

about 5 months ago
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Computing a Cure For HIV

gentryx Yesno? (89 comments)

It's not that specialized. It's just plenty of DSPs strapped together on a torus.

Actually Anton uses ASICS, their cores are specially geared at MD codes. This goes way beyond just "strapping together DSPs". They have IIRC ~70 hardware engineers on site. (Source: I've been to DE Shaw Research last year).

Unlike what wikipedia claims, you could probably achieve comparable performance using a more classical and general-purpose supercomputer setup with GPU or Xeon Phi accelerators, provided the network topology is well tuned to address this sort of communication scheme

No, you can't, and here is why: Anton is built for strong scaling of smallish, long running simulations. If you ran the same simulations on a "x86 + accelerator" system (think ORNL's Titan) then you'd observe two effects:

  • The GPU itself might idle a lot as each timestep only involves few computations, leaving many shaders idle or waiting for the DRAM.
  • Anton's network is insanely efficient for this use case. IIRC it's got a mechanism equivalent to Active Messages, so when data arrives, the CPU can immediately forward it to the computation which is waiting for it. That leads to a very low latency compared to a mainstream "InfiniBand + GPU" setup.

(most recent supercomputers don't use tori)

Let's take a look at the current Top 500:

  • #1 Tianhe-2: Fat Tree
  • #2 Titan: 3D Torus
  • #3 Sequoia: 5D Torus
  • #4 K Computer: 6D Torus
  • #5 Mira: 5D Torus
  • #6 Piz Daint: 3D Torus
  • #7 Stampede: Fat Tree
  • #8 JUQUEEN: 5D Torus
  • #9 Vulcan: 5D Torus
  • #10 nn: 3D Torus

So, torus networks are the predominant topology for current supercomputers.

about 6 months ago
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The Revolutionary American Weapons of War That Never Happened

gentryx Missing: Project Pluto (133 comments)

Granted, it sounds a tad like an episode from Thunderbirds, but it's real: Project Pluto was a nuclear powered Supersonic Low Altitude Missile (SLAM). The idea was to drive the reactor into critical state and superheat the inflowing air, efficiently creating a nuclear powered scamjet. Downside: because the reactor was almost unshielded, all controls had to be designed to withstand extreme radiation and heat (they had to work in white heat conditions). The project was canceled in the 60s, but they actually built and powered up the engines.

about 6 months ago
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Computing a Cure For HIV

gentryx /Very/ different hardware (89 comments)

Computational drug design and bitcoin miners have in common that both run best on custom hardware. The crux is, that both require very different types of hardware. As an example, please refer to Anton, designed by DE Shaw Research exactly for molecular dynamics (MD) codes.

Bitcoin mining is classified as a so called embarrassingly parallel algorithm, while MD is a tightly coupled problem. Hence an efficient parallelization for MD codes is much harder to speed up: communication gets in the way, and communication is essentially always bound by the speed of light.

ps: fun fact: bitcoin mining and MD can be carried out (at least somewhat) efficiently on GPUs.

about 6 months ago
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The Truth About OpenGL Driver Quality

gentryx Richie rich? (158 comments)

OT: "Geldreich" is a German compound of Money (Geld) and rich/plentyful (reich). So if he's called Rich Geldreich, that could be written as Rich Rich... Yeah, I know: no one knows Richie Rich today.

about 7 months ago
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Why Scientists Are Still Using FORTRAN in 2014

gentryx Re:Arrays! (634 comments)

Boost multi_array is pretty powerful and supports all sorts of slices.

about 7 months ago
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Mathematicians Push Back Against the NSA

gentryx +1 (233 comments)

History is full of tragedies facilitated by people "just doing their job".

Source: I'm from Germany.

about 8 months ago
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Neovim: Rebuilding Vim For the 21st Century

gentryx Re:Broken link (248 comments)

I hope you refer to the carpal tunnel syndrome, b/c a carpel tunnel is definitely something I'd rather not have in my body.

about 9 months ago
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Neovim: Rebuilding Vim For the 21st Century

gentryx Re:Broken link (248 comments)

EMACS OTOH is increasingly getting replaced by all kinds of IDE's and what not. The number of new users are dwindling, it has no future.

*citation needed

about 9 months ago
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'Google Buses' Are Bad For Cities, Says New York MTA Official

gentryx Foxconn and friends were faster (606 comments)

Foxconn is already doing arcologies. Workers never have to leave the company's premises. I don't know whether they already include graveyards.

about 10 months ago
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Mt. Gox Gone? Apparent Theft Shakes Bitcoin World

gentryx Catching the stolen bitcoins... (695 comments)

The list of robbed Bitcoin exchanges is long and growing. In almost all cases the stolen coin can be traced (since all transactions are public thanks to the protocol). I wonder if the running exchanges have some sort of blacklist that detects whether previously stolen funds get moved to their wallets and if they will confiscate those.

about 10 months ago
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Slashdot PT Cruiser Spotted In the Wild

gentryx Re:In Germany... (94 comments)

...or humor.

about 10 months ago
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Engineers: Traffic Studies Use Simulation Software, Not Lane Closings

gentryx Actual scientific traffic sim (265 comments)

For the curious: here is a link to Sumo, which is a real, scientific traffic simulation software developed by the DLR in Germany.

about a year ago

Submissions

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A C++ library that brings legacy Fortran codes to supercomputers

gentryx gentryx writes  |  about a year ago

gentryx (759438) writes "In scientific computing a huge pile of code is still written in Fortran. One reason for this is that codes often evolve over the course of decades and rewriting them from scratch is both risky and costly. While OpenMP and OpenACC are readily available for Fortran, only few tools support authors in porting their codes to MPI clusters, let alone supercomputers. A recent blog post details how LibGeoDecomp (Library for Geometric Decompostition codes), albeit written in C++, can be used to port such codes to state-of-the-art HPC systems. Source code modification is required, but mostly limited to restructuring into a new pattern of subroutines."
Link to Original Source
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LibGeoDecomp 0.2.0: an auto-parallelizing computer simulation library for C++

gentryx gentryx writes  |  about a year and a half ago

gentryx (759438) writes "The LibGeoDecomp (Library for Geometric Decomposition codes) project has recently released its version 0.2.0. The library can be used together with a huge variety of models, ranging from LBM (CFD, stencil codes) to molecular dynamics simulations (n-body codes). It leverages its specialized API to relieve the user from parallelizing his code and scales on virtually every parallel architecture, be it multi-cores, GPUs, MPI clusters or even GPU-equipped supercomputers."
Link to Original Source
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News from Nvidia's GTC: updated Tesla/Tegra roadmaps

gentryx gentryx writes  |  about 2 years ago

gentryx (759438) writes "Today Nvidia's founder Jen-Hsun Huang has revealed two new future architectures which are currently being worked on: Volta in the Tesla line and Parker in the Tegra line. Volta will feature 3D chip stacks with through-silicone vias and 1 TB/s of memory bandwidth. Such an off-chip bandwidth would not be possible with the current technology which runs all connections through the rim of the chip. However, these stacks also increase thermal density, which may create other problems. Parker is to use FinFET transistors, which indicates that Nvidia will stick with TSMC as its fabrication partner.

Huang also announced the Nvidia GRID VCA (visual computing appliance), a machine stuffed with 8 dual-chip GPUs, which might be regarded as a GPU mainframe by some, or, since it runs virtual machines, a GPU cloud by marketing.

More details and some key slides are available here."

Link to Original Source
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Wright Brothers Grounded: German Gustav Weißkopf Lift Off 1901

gentryx gentryx writes  |  about 2 years ago

gentryx writes "Newly found evidence supports earlier claims that Gustave Whitehead (a German immigrant, born Gustav Weißkopf, with Whitehead being the literal translation of Weißkopf) performed the first powered, controlled, heavier-than-air flight as early as 1901-08-14 — more than two years before the Wrights took off. A reconstructed image shows him mid-flight. A detailed analysis of said photo can be found here. Apparently the results are convincing enough that even Jane's chimes in.

His plane is also better looking than the Wright Flyer I."

Link to Original Source
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Humble Bundle 6 Released

gentryx gentryx writes  |  more than 2 years ago

gentryx writes "The next incarnation of the indie games Humble Bundle has been released. Games included are
  • Rochard, a sci-fi platformer
  • Shatter, a reloaded breakout clone
  • Space Pirates and Zombies, 2d, top-down spaceship arcade action
  • Torchlight, an RPG in a fantasy setting
  • Vessel, a puzzle/platform hybrid
  • Dustforce, another take on wiping the dust of the platformer genre
"

Link to Original Source
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Controlled Quantum Levitation Used To Build Wipeou

gentryx gentryx writes  |  more than 2 years ago

gentryx writes "Researchers at the Japan Institute of Science and Technology have build a miniature wipE'out" track using high temperature superconductors and quantum levitation. Right now this is fundamental research, but in the future large scale transportation systems could be build with technology akin to this.

I have a different vision: let Nintendo sell this as an accessory for the Wii U. I'd buy several of these tracks, let the gliders race through the whole house and track them on our TV!"

Link to Original Source
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Trillion-frame-per-second Camera Captures Propagat

gentryx gentryx writes  |  about 3 years ago

gentryx writes "MIT has published a story on how the fastest camera on earth can capture a trillion frames per second, making it possible to trace for instance how a laser pulse moves through a bootle (more footage here). Ramesh Raskar, one of its inventors, also calls it the world's slowest camera, since the actual capture of the image sequences takes hours. The reason for this is that the camera doesn't take 2d pictures, but just 1d streaks — at a very high framerate. To obtain a 2d movie, the camera has to film the same experiment over and over again, tilted at different angles. However, in its intended use-case the camera only has to take 1d frames anyway: it is meant to study light absorption of molecules."
Link to Original Source
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Autonomous cars navigate Berlin's traffic

gentryx gentryx writes  |  more than 3 years ago

gentryx (759438) writes "Coumputer driven cars have been frequently featured here on Slashdot. After Google testing their cars in traffic, a German team has sent their car through the city of Berlin, which is notorious for its chaotic and dense traffic. It did negotiate the track multiple times, without accidents. The car, dubbed MadeInGermany, is a VW Passat, and has been equipped by TU Berlin with laser scanners, radar, cameras, and odometers — a setup comparable to Google's cars."
Link to Original Source
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One Step Closer to Mind-Reading Machines

gentryx gentryx writes  |  more than 3 years ago

gentryx writes "Researchers at Berkeley have come up with a brain model to reconstruct what you are seeing, using only fMRI measurements and a library of YouTube clips. Possible future uses could be to visualize what comatose or blind patients are seeing, or even to record dreams. Looks like just another one of William Gibson's predictions have come true (after e.g. the Cyberspace). The videos (2nd video, paper) are still blurry, but it's frightening to imagine what could be done with a more precise model and a stealthy fMRI. Ladies and gentlemen: don your tin foil hats!"
Link to Original Source

Journals

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Controlled Quantum Levitation Used To Build Wipeout Track

gentryx gentryx writes  |  more than 2 years ago

Researchers at the Japan Institute of Science and Technology have build a miniature wipE'out" track using high temperature superconductors and quantum levitation. Right now this is fundamental research, but in the future large scale transportation systems could be build with technology akin to this.

I have a different vision: let Nintendo sell this as an accessory for the Wii U. I'd buy several of these tracks, let the gliders race through the whole house and track them on our TV!

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LibGeoDecomp: an Auto-parallelizing Stencil Code Library

gentryx gentryx writes  |  more than 3 years ago

LibGeoDecomp is a C++ class template based library which provides a smooth transition for researchers to port their existing stencil based simulation codes to parallel computers -- from multi-cores to MPI clusters and GPGPUs. In a nutshell, one only has to replace the accesses to neighboring elements by the library functions and let LibGeoDecomp handle the main time and space loops. Essentially the library takes over the parallel programming part, which can be of great help for scientists who'd rather focus on the physics (or chemistry or what ever) part of their research and less on the computer science required to carry it out.
  It's currently in alpha state, but is already being used for medium sized simulations requiring 200 GB of RAM and prodicind 2 TB of output data.

DISCLAIMER: yes, this this my PhD project, so I'm biased.

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One Step Closer to Mind-Reading Machines

gentryx gentryx writes  |  more than 3 years ago

Researchers at Berkeley have come up with a brain model to reconstruct what you are seeing, using only fMRI measurements and a library of YouTube clips. Possible future uses could be to visualize what comatose or blind patients are seeing, or even to record dreams. Looks like just another one of William Gibson's predictions have come true (after e.g. the Cyberspace). The videos (2nd video, paper) are still blurry, but it's frightening to imagine what could be done with a more precise model and a stealthy fMRI. Ladies and gentlemen: don your tin foil hats!"

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