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Comments

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Bug In the GnuTLS Library Leaves Many OSs and Apps At Risk

cnettel Re:Function call overhead (231 comments)

Nested blocks are refactorable into smaller functions.

And the program eats the function/method/message call overhead, the overhead of passing all local variables as arguments, and the overhead of constructing and destroying an object through which to return multiple values from each function call.

I think you need to be introduced to a modern optimizing compiler. It will handle the first two for you, just fine, as long as you are in the same compilation unit (or doing fancier global optimziation). Since you just refactored this from a single function, you are supposedly still in the same compilation unit. If you pack the data in something like a stack-allocated struct even the last one will be reduced or completely avoided.

about a month and a half ago
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Bug In the GnuTLS Library Leaves Many OSs and Apps At Risk

cnettel Re:Freedom is better than dependency. (231 comments)

The Apple library itself was open source, right (although rebuilding the OS files would be precarious in OS X and outright impossible in iOS)? The mess with libraries like this (proprietary or not) is all other code (proprietary or not) that not only link to shared objects provided with the OS, but roll their own, sometimes even modified, build of the library. Now, thanks to the fact that it's GPL it cannot be hidden in a blob without at least a license notice, but tracking it down everywhere will be a mess. And then we haven't even got started about embedded systems...

about a month and a half ago
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Japanese Firm Proposes Microwave-Linked Solar Plant On the Moon

cnettel Re:Gravity wells and other distance issues (330 comments)

Go to the company website instead. They say lunar resources and are able to tell the difference between kms and miles. However, it's all a bit pie in the sky even there. Even with the advantage of lunar resources, I would be more optimistic about geostationary orbital solar power. Microgravity would mean that you could get away with really thin structures, even concentrated thermal solar might make sense if you can work out a reasonable cooling part of the cycle (just make an extremely thin mirror as the bulk of the concentrator).

about 2 months ago
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Japanese Firm Proposes Microwave-Linked Solar Plant On the Moon

cnettel Re:is that really better than earth based? (330 comments)

Solar insolation on the moon is not dramatically higher than on Earth - around 1400 W/m^2 versus around 1000 W/m^2 on Earth. Granted, a Lunar solar station wouldn't be affected by weather, but Earth based receivers will suffer from efficiency loss during bad weather.

Could they achieve the same result by building a bit larger system on earth, but without the hundreds (or thousands?) of rocket launches it would take to get the materials to the moon to get the thing started?

Besides, who wants to see a big black ribbon around the moon?

They plan to use lunar materials, so no hundresds of rocket launches to get started. I guess the point is kind of that real estate and raw materials are "free", if you get the proper manufacturing equipment up there. If that equipment is automated enough, you can build up slowly, but steadily.

about 2 months ago
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Customer: Dell Denies Speaker Repair Under Warranty, Blames VLC

cnettel Re:Just don't do it (526 comments)

How about putting a filter (low-pass/high-pass - I'm not an audio engineer, so I don't know) to stop any of the "damaging" waveforms from reaching the speaker? It's probably just a capacitor or inductor in line with it and you could get away with the same shoddy speaker that wouldn't blow from the clipped signal.

And in all likelihood you would have (non-negligible) worse sound performance for any sane waveform you played. BTW, you could easily script a mechanical hard drive to power off and power on, all the time, for days and days. I am pretty sure a lot of drives would fail in the first year and I would honestly not want the manufacturer to honor the warranty if the total power on count exceeded half a million (powering on once per minute every minute for a year), even though it was all "legal instructions given to the machine".

about 2 months ago
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World-First Working Eukaryotic Cell Made From Plastic

cnettel Re:Not a cell (109 comments)

In other words, they made very neat bags of mostly water.

about 3 months ago
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Intel's Knights Landing — 72 Cores, 3 Teraflops

cnettel Re:Intel's version of a IBM/Sony Cell CPU (208 comments)

Plus writing software that uses 72 cores is such a walk in the park

Some stuff actually is. It depends on how trivially parallel the problem is. With some stuff there is no interaction at all between the threads - feed it the right subset of the input - process the data - dump it out.

More importantly, for some applications a limited amount of very low-latency/high-bandwidth communication is enough to give spectacular performance improvements. In those cases, the fully coherent x86 model, kept up by this kind of cache and memory architecture, will do wonders, compared to an MPI implementation with weaker individual nodes, but also possibly against (current) nVidia offerings. It's harder to say how it will stack up against Maxwell.

about 4 months ago
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Intel's Knights Landing — 72 Cores, 3 Teraflops

cnettel Re:Not going to work (208 comments)

20 years? I would be very doubtful regarding any prediction beyond the point where current process scaling trends finally break. Note, they might break the other way. Switching to a non-silicon material might allow higher frequencies which will again shift the tradeoff between locality, energy, and production cost. But there is no reason, no reason at all, to expect the current style to last for more than ten years, while you could be quite right that it could stay much the same for the next five years or so.

about 4 months ago
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Linux x32 ABI Not Catching Wind

cnettel Re:Seems reasonable. (262 comments)

Not really. For an x32 binary, you would have x32 libc and use all the fancy features. For an x86 binary running on an AMD64 processor, you are still stuck in "compatibility mode" on the processor, even when you enter libc, which means you can only use actual x86 instructions (with the smaller register file etc). It is my impression that on-the-fly switching between long and compatibility mode within the same proecss would still incur a cost that's comparable to (at the very least) a kernel mode transition, so the benefits would only exist for very few operations. Large memcpys wouldn't be among them, since the x86 vector instructions are actually quite fine for that purpose.

about 4 months ago
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Linux x32 ABI Not Catching Wind

cnettel Re:Seems reasonable. (262 comments)

There's plenty of applications around still without a 64 bit binary. From what I understand this layer just allows 32 bit programs to utilize some performance enhancing features of 64 bit architecture. It seems a genuinely good idea.

It allows 32-bit programs, which are *recompiled*, to benefit from those features. You still need the source and x32 builds of all dependencies. However, sometimes I guess there could be porting issues due to pointer size assumptions (but no other hard assumptions of x86 ABI behavior). Those codebases could not be recompiled for x64, but might port to x32 more easily.

about 4 months ago
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Linux x32 ABI Not Catching Wind

cnettel Re:Nice concept (262 comments)

Any application that does heavy-numerical computation should not be affected by much by the ABI if at all. All function calls are inlined inside the critical loop.

The ABI here also defines the size of all pointers. All pointers are 32-bit here. Any purely compute intensive application will not be affected much, but something including some complexity in data structures, with pointers, could possibly benefit a lot. On the other hand, if all your code does is traversing trees, you should seriously consider allocating them in one bunch and using internal indices (of smaller integer type) rather than native pointers anyway.

about 4 months ago
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Airgap-Jumping Malware May Use Ultrasonic Networking To Communicate

cnettel Re:What a load of complete rubbish! (265 comments)

It all depends on what timespan you have. All you need to do is to emit sounds that are quite inaudible or at least indistinguishable from high frequency noise that we have been trained to accept (PWM noise from LCD brightness control etc). If you have plenty of time, you can reduce your bitrate heavily in the handshaking step, basically looking for just a few bits of signature in a very wide span of frequencies and encodings. When you have a basic channel, you can tell your counterpart what SNR you are getting and successively tune the channel.

You would never want this for regular networking with any kind of latency demands. If you are rather just trying to get a specific updated payload across at some point, with any number of retransmissions, then I find it quite believable.

about 6 months ago
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Ask Slashdot: How To Diagnose Traffic Throttling and Work Around It?

cnettel Re:NSA (251 comments)

I suppose in very specific cases it could be worth it to intentionally make an encrypted channel unusable, in order to try to lure a target into using an unencrypted channel. But, as you say, doing so (and manifesting that you have that ability) comes at a rather great cost in terms of non-covertness.

about 7 months ago
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Same Programs + Different Computers = Different Weather Forecasts

cnettel Re:Have these people never heard of IEEE754???? (240 comments)

It doesn't help you that individual operations are rounded deterministically, if the order of your operations is non-deterministic. You cannot expect bit-identical results if you parallelize or allow any level of operation reordering. Even a very well-written code might implement a reduce operation in different hierarchies depending on memory layout. Enforcing all these things to be done in the exactly same order, with full IEEE754 compliance is a significant performance cost. By taking numerical aspects into account, you can ensure that your result is not invalid or unreasonable. However, for a chaotic problem where a machine epsilon difference in input data might be enough for a macroscopically different end result, there is nothing you can do and still expect reasonable utilization of modern architectures.

about 9 months ago
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Same Programs + Different Computers = Different Weather Forecasts

cnettel Re:Have these people never heard of IEEE754???? (240 comments)

No, it isn't, when the system itself is not well-conditioned. And I bet you don't want your compiler to run a real codebase in a IEEE754 strict interpretation, as that will disallow almost any optimization. Even if you would allow it, then "trivial" rearrangements, that don't affect the theoretical analysis of stability, correctness or condition number, will still introduce different rounding perturbations. Perturb weather or some other systems, and you will get a completely different trajectory.

That said, many applied fields, including meteorology, could benefit from more well-disciplined computational science approaches. But don't expect all that much of a difference.

about 9 months ago
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Ask Slashdot: Hardware Accelerated Multi-Monitor Support In Linux?

cnettel Re:Multi-Monitor Support in 2013?!? (278 comments)

Wrong. It was totally OK in XP. It was Vista that broke it for WDDM (the new driver model), but I think 7 fixed it "back".

about 9 months ago
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Google's Latest Machine Vision Breakthrough

cnettel Re:Coming to mobile? (113 comments)

"...might bring high power visual recognition to simple desktops and even mobile computers... computed in less than 20 seconds using nothing but a single, multi-core machine with 20GB of RAM."

Right... and by mobile computers you mean computers that I can lug from one desk to another.

Like the MacBook Pro Retina with 16 GB? The point of their approach seems to be lots and lots of RAM to do table lookups. The memory subsystem in a normal laptop is plenty fast for that. Bandwidth would be more of a problem than total space in a cellphone. If we had a compelling case for loads of RAM in a smartphone, it would be possible to design one without going wildly beyond current power or cost envelopes. A few more years of Moore and things will be fine.

about 9 months ago
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Is the World's Largest Virus a Genetic Time Capsule?

cnettel Re:Small threat to people? (111 comments)

The article, as in scientific paper, is quite clear on this. There is no signs that anything close to vertebrates are infectable.

about 9 months ago
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Is the World's Largest Virus a Genetic Time Capsule?

cnettel Re:Hoip! (111 comments)

RTFA, they believe the size makes it look like juicy food.

about 9 months ago
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Linux 3.11 Officially Named "Linux For Workgroups"

cnettel Re:what? (376 comments)

Much like Windows 3.11 the GUI in GUN/Linux isn't a core part of the OS - but a graphics server with window managers on top and all the real work being done by the OS under the manager.

That is true, but the similarity doesn't go much further than that. If you look at the capabilities of the OS underneath, there is a major difference between Linux and DOS. (Even to this day some of the limitations inherited from DOS are still found in modern Windows versions. The last Windows user I came across wasn't able to open a command line window more than 80 characters wide.)

Yeah, opening the properties or using the MODE command is a terrible pain. By the way, Windows 3.1 in 386 mode didn't really put a fancy face on top of DOS. It is rather like a headcrab or something. It might rely on some of the services of the host, but it also modifies it beyond recognition. Virtual memory management and yes, some network services, lived almost solely in the Windows product, e.g. HIMEM.sys existed, but all the logic was in Windows.

about 9 months ago

Submissions

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http://support.microsoft.com/kb/943899

cnettel cnettel writes  |  more than 6 years ago

cnettel (836611) writes "It's that special time of the month when every MS sysadmin gets a warm fuzzy feeling. It's Patch Tuesday! But, who cares about a remote execute vulnerability in the TCP/IP stack of Windows (XP and up, the critical one is in the IGMP support), when there is an update that improves disk performance in Vista? Now, let's see if the remaining copy time can get from infinity to something low, like negative..."

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