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Comment: Original sources (Score 2) 126

by enriquevagu (#47775417) Attached to: Research Shows RISC vs. CISC Doesn't Matter

It is really surprising that neither the linked Extremetech article, nor the slashdot summary cite the original source. This research was presented in HPCA'13 in a paper titled "Power Struggles: Revisiting the RISC vs. CISC Debate on Contemporary ARM and x86 Architectures", by Emily Blem et al, from the University of Wisconsin's Vertical Research group, led by Dr. Karu Sankaralingam. You can find the original conference paper in their website.

The Extremtech article indicates that there are new results with some additional architectures (MIPS Loongson and AMD processors were not included in the original HPCA paper), so I assume that they have published an extended journal version of this work, which is not yet listed in their website. Please add a comment if you have a link to the new work.

I do not have any relation with them, but I knew the original HPCA work.

Comment: Re:Men and women not the SAME!! (Score 2) 75

by Geoffrey.landis (#47659689) Attached to: Maryam Mirzakhani Is the First Woman Fields Medalist

Men and Women are not the same. Men tend to spread out wider both dumber and smarter then the mean aka they have larger standard deviation then women in both intelligence and sanity level.

This is a hypothesis. You are stating it as a fact.

The evidence for this hypothesis is, at the moment, quite weak.

Evidence for this hypothesis would be best found by examining a society in which males and females are given identical treatment, and not given different social cues childhood or raised to different expectations. I'm not sure where you find that society.

Comment: Problem and possible alternatives (Score 5, Informative) 131

This is a real pity for the TM community. This is not the first chip with transactional memory support in hardware: The Sun Rock was announced to have hardware TM support, and the IBM Blue Gene/Q Compute chip also supports it. Unlike other proposals for unbounded transactional memory, all these systems employ Hybrid Transactional Memory (ref, ref, ref), in which restricted hardware transactions are designed to correctly coexist with unbounded software transactions, so a software transaction can be started in case a hardware transaction fails for some unavoidable issue (such as lack of cache size or associativity to hold speculative data from the transaction, not because of a conflict). Note that, in any case, very large transactions should arguably be very uncommon, since they would significantly reduce performance (similar to very large critical sections protected by locks).

The problem with the hardware implementation of transactional memory is that they are not simply a new set of instructions which are independent from the rest of the processor. HTM implies multiple aspects, including multiversioning caching for speculative data; allowing for the commit of speculative (transactional) instructions, which could be later rolled back (note that in any other speculative operation such as instructions after branch prediction, the speculation is always resolved before instruction commits because the branch commits earlier); a tight integration with the coherence protocol (see LogTM-SE for an alternative to this very last issue, but still...); a mechanism to support atomic commits in presence of coherence invalidations... From the point of view of processor verification, this is a complete nightmare because these new "extensions" basically impact the complete processor pipeline and coherence protocol, and verifying that every single instruction and data structure behaves as expected in isolation does not guarantee that they will operate correctly in presence of multiple transactions (and non-transactional conflicting code) in multiple cores. There are some formal studies such as this or this, and the IBM people discuss the verification of their Blue Gene TM system in this paper (paywalled).

As some others commented before, the nature of the "bug" has not been disclosed. However, since it seems to be easy to reproduce systematically, I would expect it to be related to incorrect speculative data handling in a single transaction (or something similar), rather than races between multiple transactions.

Regarding the alternatives, Intel cannot simply remove these instructions opcodes because previous code would fail. I assume that the patch will make all hardware transactions fail on startup, with an specific error (EAX bit 1 indicates if the transaction can succeed on a retry; setting this flag to 0 should trigger a software transaction). In such case, execution continues at the fallback routine indicated in the XBEGIN instruction, which should begin a software transaction. Effectively, this will be similar to a software TM (STM) with additional overheads (starting the hardware transaction and aborting it; detecting conflicts with nonexistent hardware transactions) that would make it slower than a pure STM implementation.

Comment: They are right - Uses of unicode ambiguous letters (Score 1) 79

They are right doing so. There are letters in different alphabets whose typing is very very similar -- or in fact they are written exactly the same, depending on the font used.

This can be exploited for interesting uses. For example, "E" and "ÃZ"** are respectively the latin "e" and the greek "epsilon" vowels, but they are indistinguishable in caps, at least in Arial font. The second one is the UTF 395 code. My name has an "E" on it, and for my email signature I spell my name using the traditional latin letter from the keyboard when the email is important and should be archived. By contrast, when the email is mostly irrelevant for future use (such as meeting arrangement emails, which are useless after the meeting takes place) I spell my name using the Greek epsilon letter (hint: 395 followed by Alt+X in most Windows programs). There is no obvious difference for the receiver, but a search tool can be used to quickly find all sent emails which can be deleted safely.

While the previous is a somehow "legit" use, in general any word which combines letters from different alphabets could be used to confuse an trick the receiver, for example by creating an email account which reads exactly the same as the one from another person. There is a nice image of 5 letters a-b-c-d-e in different alphabets in the linked post. I agree with Google in preventing such combinations for email accounts. It would be interesting to know the exact policy used to forbid account names, which is not detailed.

** At the time of writing, these two letters look exactly the same. Classic Slashdot lacks Unicode support and does not represent the greek Unicode letter from my comment. I tried logging into Slashdot Beta (first time, I swear it!!) and it seems to represent a different letter... Please try this on your own computer!

Comment: The problem is false negative (Score 3, Insightful) 383

by Geoffrey.landis (#47646663) Attached to: DARPA Wants To Kill the Password

What happens if you get sick or injured? Can you imagine pink eye with retinal scanners?

Yes, this is the serious problem-- just as serious as the problem of people fooling the password-alternative is the problem of the false negatives: getting locked out.

Notice that most of these weren't fingerprint scanners or retinal scanners-- they were stuff like gait monitors, or even more bizarre stuff, like listening to your heartbeat. So, if you twist your ankle--or even buy a new pair of shoes-- you're out of luck. Taking pseudoephedrine for a cold? Ooops, your heartrate is different. You're locked out.

--instead of using these instead of password, however, what about if you use alternate ID as a second check. It doesn't lock you out, but it does trigger a watchdog alert that pays attention to what you're doing.

You can change a password, you can't change your retina print. What do you do when your account is compromised? Get new eyes?

Yes, we've all seen dozens of those science fiction stories where they steal people's eyes, or cut off their fingers, or take swabs of their DNA.

Comment: 2nd law [Re:microwave bright [Re:Oh good lord.]] (Score 1) 225

by Geoffrey.landis (#47645921) Attached to: Do Dark Matter and Dark Energy Cast Doubt On the Big Bang?

If a civilisation could create a Dyson sphere, don't you think they'd have some use for all the wasted energy "radiating in infrared"?

If they can get usable energy out of waste heat, they have a means of getting around the second law of thermodynamics. It's hard to guess what a technology with that much sophistication can do, but if they can do that, they don't need to surround a star with a shell to harvest energy.

Comment: microwave bright [Re:Oh good lord.] (Score 3, Insightful) 225

by Geoffrey.landis (#47642631) Attached to: Do Dark Matter and Dark Energy Cast Doubt On the Big Bang?

well, if Dyson spheres are anywhere near the size of the solar system, they would radiate in the infrared. Longer infrared the larger they are.

You could imagine a Dyson sphere that is vastly larger than a solar system -- like, a hundred AU across, or so--that would radiate waste heat in millimeter wave, or even something vastly larger than that that would radiate in microwave.

But, of course, that doesn't solve the problem-- they would be shine like beacons to radio telescopes.

Comment: Re:More money just increases the price (Score 3, Interesting) 118

by Geoffrey.landis (#47631417) Attached to: Cornering the Market On Zero-Day Exploits

If a new buyer comes into the market - a buyer with lots of money, then all that happens is that the price goes up. It's simple economics

Well, yes, but that's exactly what was desired:
You want the price to go up, so that it's more valuable to disclose the bug than it is for some thief exploit it.

If the price becomes high enough, new exploiters will enter the market and start discovering exploits

Exactly. You mine out the easy-to-find exploits until they are depleted, and start in on the harder-to-find bugs, so that you get to the point where amateur hackers simply aren't sophisticated enough to find them.

... After all, we haven't seen a government agency buying up all the drugs, in order to stop them being supplied to the population

Well, of course you can always manufacture more drugs; you don't "find" them. They don't get harder to make as the market increases.

If the objection here is "software companies will start deliberately introducing vulnerabilities, so that they can make money by selling the vulnerabilities to the government"-- yes, that might be an objection.

Comment: Re:A little behind the times (Score 1) 315

by Geoffrey.landis (#47630001) Attached to: Why the "NASA Tested Space Drive" Is Bad Science

That your comment got modded 5:informative is hilarious. How about you RTFM and not phrase your comment in the form of questions? This was NASA. If NASA believed any of those alternate explanations you cited, do you think they'd be stupid enough to damage their reputations by presenting this absent those prominent criticisms?

Just as a minor correction, this was one lab group, at one NASA center. It was not "NASA" collectively.

NASA is not a monolithic entity. Other scientists at other parts of NASA have expressed some amount of skepticism about the conclusion that the experimental results quoted are best explained as the thruster producing anomalous thrust. We all want to see these results carefully replicated.

It would be better if these results had been reported as "here's a preliminary anomalous result that needs to be verified," instead of "OMG, a space drive!"... but they weren't.

Comment: What it was not about [Re:The article is flat-o... (Score 1) 315

by Geoffrey.landis (#47629875) Attached to: Why the "NASA Tested Space Drive" Is Bad Science

Oh for fuck's sake... Time to debunk this shit, again.
TFA got it wrong as well, so I suppose I can't blame you people for getting it wrong too, but please try doing a little more research?
A little background: The EmDrive was invented by a guy named Shawyer.

I have have a copy of the paper in question, "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum," and have read it in detail. It does not reference Shawyer. This paper is not about the "EmDrive."

It was tested by NASA, among others, and found to produce about 91 microNewtons. (I'll address the 30-50 that TFA talks about too.) That's way less than the Chinese found, but NASA was also testing it at much lower power and say they are planning to test a higher-power version.

"Way less" means "over four orders of magnitude less." The Juan et al. test-- reference 1 in the paper-- did not test a thruster at hundreds of kilowatts input power! At best, you can say that the JSC test was testing something different form the Chinese test. They did not replicate the Chinese tests in any way.

...To test this, two versions of the Cannae Drive were (also, separately from the EmDrive test) tested by NASA: one with and one without the slots. Those tests both produced the same thrust (30-50 microN, about half what the EmDrive produced), which disproves Fetta's theory as to how the Cannae Drive is supposed to work.... and nothing else The null test device that everybody is so dismissedly claiming claiming disproves the EmDrive wasn't even supposed to be an EmDrive!

The EmDrive was not mentioned or referenced in the paper being discussed.

Fetta, inventor of the Cannae Drive, was disproven.

Correct. This is a valid conclusion of the results of the paper.

Shawyer, inventor of the EmDrive, was actually vindicated because according to his theory, the Cannae Drive (slots or no) is basically an inefficiently-shaped EmDrive.

Shawyer was not mentioned nor referenced in the paper. The EmDrive was not mentioned nor referenced in the paper.

I don't know why this is so hard for people to understand.

It is hard for people to understand because in an article about the results of a paper "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum," you reference a garbage-dumpster full of other stuff that is not mentioned nor referenced in that paper.

Comment: Re:BLINDED BY SCIENCE !! (Score 1) 315

by Geoffrey.landis (#47629583) Attached to: Why the "NASA Tested Space Drive" Is Bad Science

Any 2nd year physics student should be able to laugh this garbage right off a lab bench without even running an experiment.

And laughing this off without even running an experiment is precisely the wrong thing to do.

Science is about replication. Replication requires doing the experiment. Or, at a minimum, not laughing at other people who do the experiment.

Now: the actual results of the experiment are pretty minor. The results they show, first, didn't replicate the results that they were attempting to verify, second, falsify the hypothesis that they were testing, and, third, are pretty low in magnitude-- probably spurious, in my (professional*) opinion.

The article explains why any good scientist should be able to laugh this off based on the reported experimental results.


This is the way science is done: you test stuff. You present your results. Other scientists then critique the results, point out flaws and sources of noise and bias.

It's rather brutal, actually. But if your result holds up to the criticisms (and most don't), maybe you've pushed the boundaries of science.

These results don't-- yet. They are not yet reporting consistent results (in that their results differ significantly from those of other researchers). They have not yet eliminated possible spurious effects.

That's science.

*in fact, I am a rocket scientist

Comment: Mostly Dutch (Score 1) 81

"The Wikimedia Foundation this morning reports that 50 links to Wikipedia from Google have been removed under Europe's "right to be forgotten" regulations,..."

Looking at the Wikipedia page listing the notifications they've received of pages removed from the european search engine https://wikimediafoundation.or... , two were english wikipedia, two wre italian, and the remainder are all nl.wikipedia-- Netherlands.

So, apparently the Dutch have much more desire to be forgotten than the rest of Europe. (Or else, possibly, they're just more efficient at getting the right-to-be-forgotten notices out)

Nature, to be commanded, must be obeyed. -- Francis Bacon