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Comment: Re:Exact mathematical value isn't the ideal (Score 2) 238

by whit3 (#48118081) Attached to: Where Intel Processors Fail At Math (Again)

The error is not small. If you read the article, on certain very reasonable inputs (not pathological at all), you can sometimes wind up with only _four_ bits being correct.

The issue here, is that any computed sine value outside the first quadrant (input values 0 to pi/2) is computed by reducing the input quantity. The function is periodic, so adding or subtracting any multiple of the period (2 pi) from the input value, is mathematically valid. So, the error is made to be small for each value in that first quadrant, and the Intel documentation correctly quotes the errors there. The 'reducing the input quantity' step, however, doesn't use extended precision arithmetic, so the (add 2pi) step adds roundoff error (and that roundoff error generates output errors).

Thus, the sin(1.14159) calculation, with a 10-decimal-place accurate representation of that number (1.14159), gives roughly a 10-decimal-place determination of the proper sine value. But, the sin(1.14159 x 10**9) will get LOTS of leading digits truncated when you scale the input, and can only determine a 1-decimal-place scaled input value, thus only a 1-decimal-place sine.

And, if the hypothetical, perfect, sine value has leading zeroes, it looks terrible as a 'percent error'. Any roundofff error at all, in a sin(3.14159265358979323846264338...) calculation, will get a divide-by-zero boost when you calculate a percent error. The absolute error, though, is just what is to be expected from roundoff error in a step that takes the remainder after dividing by (2pi + roundoff_error(2pi) ).

Comment: Re:Fox News? (Score 1) 460

by whit3 (#48029251) Attached to: Scientists Seen As Competent But Not Trusted By Americans

The biggest problem is that anyone can call themselves a scientist. There really is not definition of what it takes to be qualified as a scientist. One who practices science regardless of comptence?

In the science community, of course, this isn't a problem. One can look up the author's peer-reviewed
publications, and judge from that.
Outside the science community, alas, there won't be much access to (or comprehension of) that
information. Scientists won't offer any (vague, general, personal) interpretive comments if they can avoid it.

As a rule, a scientist publishes his best work, and its supporting data and reasoning, in a peer-reviewed
setting. There's no reason a prudent observer would look beyond that body of published work,
but any reporter will be imprudent, to jazz it up for a news story. General, vague, and personal are the hooks that get attention, in a one minute spot.

Comment: Maybe it will, Re:This won't amount to anything... (Score 1) 122

by whit3 (#47936833) Attached to: Scientists Twist Radio Beams To Send Data At 32 Gigabits Per Second

It's been shown that all these "helical" polarization schemes are degenerate forms of MIMO essentially, and can't achieve speeds better then what MIMO antenna configurations can.

While it may be argued that circular polarization is another MIMO scheme, it CAN achieve better speeds, because it DOESN'T REQUIRE EXTRA CHANNELS. MIMO, generally, does. There's nothing 'degenerate' about the relationship of the two schemes.

The real limitation here, is that this is a beam technology, it isn't for broadcast (i.e. you have to aim the sender and receiver antennae). The article mentions a 'phase plate', which implies the beam is directed perpendicular to the plane of that plate...
The real benefit, is that you get a factor of two without using any extra bandwidth from the available RF allocation.

Comment: Re:Two dimensional? (Score 1) 49

by whit3 (#47780391) Attached to: Scientists Craft Seamless 2D Semiconductor Junctions

It's possible to make a lot of approximations, and some of them depend on the dimensionality.
Three atoms thick is close enough to two dimensional that a lot of the (quantum mechanical)
calculations ARE 2-D.
So, the distinction makes sense (and there's precedent in so-called quantum dot structures)
to call this two-dimensional.

Alas, I'm unsure how one would create such a thing
and keep it intact for a substantial service life with an oxygen atmosphere around.

Comment: Re:it's explained in the study (Score 1) 86

by whit3 (#47033011) Attached to: Static Electricity Defies Simple Explanation

This water layer ion creation effect is fairly well known in materials physics. Until now, I don't think it was well known that it played any role in static generation.

While it might not be well known, it IS the best
theory I've seen for lightning (air currents and gravity sorting ice particles causing charge separation).

Comment: Re:I sent this to each of the Commissioners: (Score 1) 217

by whit3 (#46860873) Attached to: How the FCC Plans To Save the Internet By Destroying It


There are historic instances of telecommunications NON-neutrality to consider, too.
I favor internet neutrality.

Ben Franklin, as a printer in the colonies, knew the danger of selection in telecommunication;
his competitor (Bradford) in Philadelphia was also the local postmaster.
Bradford's publications were sent by post, but as for Ben's printed work

" what I did send was by bribing the riders, who took them privately,
Bradford being unkind enough to forbid it"

Our constitution was written to make telecommunication a priority of the new federal government,
"to establish post offices and post roads", and our first postmaster-general, Ben Franklin,
saw to it that postal regulations forbade favoritism. He wanted the carriers to remain
neutral. It worked well.

At the dawn of telephonic communication, a similar circumstance came up: an undertaker
thought his business suffered because a telephone operator was related to a competitor.
Mr. Strowger invented a gizmo, the Strowger Switch, that allowed a caller to connect
without talking to an operator (and dial phones worked on this principle for years).
Again, the solution to Mr. Strowger's problem was to keep telecommunications
neutral; we have all enjoyed the benefits for so long, that it seems quaint that
this ever WAS a problem.

So, at least twice before in history we have seen preference in telecommunications,
executed by carriers who had mixed motives (usually related to a profit scheme)
which caused anguish to the people of this country. Any worthy Federal Communications
Commission should exert itself to ensure that the customary fairness of
messaging is maintained into the foreseeable future. I will be watching.

Comment: Re:This approach has gone nowhere for years (Score 1) 169

by whit3 (#46818129) Attached to: Ask Slashdot: How Can We Create a Culture of Secure Behavior?

Truly, it is foolish to think millions of 'users' can be handed the
security problem, and advised to take action individually.

We should all cringe in horror when we hear that
millions of nontechnical users are being encouraged to
'take the problem seriously'. It's like asking all the residents
of an apartment building to safety-check the steam boiler (probably
only one or two will want to tighten the relief valve spring).

There have been attempts to 'take the problem seriously' with
draconian legal sentences: that, too, is doomed. The law moves
too slowly, and relies on things, like electronic documentation,
that can be SO easily corrupted.

There have been attempts to 'take the problem seriously' with
proliferation of passwords, and password-generating rules and
password replacement schedules, and by moving controls into
obscure places (what port do YOU open for SMTP?),
which entirely miss the target of security, because the poor
user has to write those things down (I know I have to!).

Instead, we should be building institutional watchers and code
(walls, if necessary, and alarms, and a few traps) to deal with
such issues. Sadly, government and commercial interests
aren't good for personal computer security- we need OTHER

Comment: Re:All publicly funded research needs public relea (Score 1) 348

by whit3 (#46790571) Attached to: VA Supreme Court: Michael Mann Needn't Turn Over All His Email

If the public pays for it, the public should receive it in its entirety.

But, this was 'freedom of information act' request, and that act refers only to
the records of government civil agencies.

The researcher had a teaching job, and acted as an independent
contractor in pursuing a research topic.

The researcher's phone calls, e-mails, piles of scratchings and musings,
aren't the proper product of his funded research at all. Only the finished report,
and/or any publishable papers (in peer-reviewed, edited journals) are
the concern of the research funding agency (probably National Science
Foundation). The NSF isn't a party to the request, they and the researcher
are presumably satisfied that the research findings WERE published.

Neither the editors of peer-reviewed journals, nor the authors, want undue
attention paid to unclear, misspelled, poorly-supported or otherwise unpublishable
debris from the research process. The researcher (and the University of Virginia)
acted properly in not handing over every tatter of e-mail that could be found. The
supreme court of the state just agreed with that.

Comment: Re:What the bill really is doing (Score 1) 32

This bill is silly. And, the arguments in McCaskill's webpage are HILARIOUS.

>>'74%' [ of articles available from other sources]

That test (this is the INTERNET we're talking about) is so ephemeral as to be meaningless.
Here this week, gone the next, or renamed, or miscatalogged (or, that page actually has
a really CUTE pic of a kitty- **awww...). Ten years from April 2014, who will be able to
locate an unedited copy of the McCaskill argument page, to understand this discussion?

>>'sold only 8%' [of the available articles, recently]

I'm pretty sure I haven't looked up anywhere near 0.1% of the listings in my local
phone directory, but I'm not burning the book to save shelf space! This also, is meaningless.

A copy of a scholarly study (which I got from NTIS and wore to tatters) is of great
value to me, and whenever I pass my work on, there will be a nice scholarly reference to it, with
NTIS being listed as the source. Anyone following good scholarship procedures will require

Kill the bill. It looks like someone : thinks libraries are run for profit; thinks bookburning
is an easy 'final solution'; perceives inefficiency; and doesn't see the increase in value of
old literature. Internet availability of articles and discussions WITH SCHOLARLY REFERENCES
means that many streams now trace to those old sources.

Comment: Re:Why Ubuntu?! {POE damage question} (Score 1) 208

In regard to probing ethernet wire combinations

...he only had 4 combinations to try. Only 4 pins of a RJ-45 are used. If it was PoE then he'd have damaged his laptop.

Since Ethernet has two (in 100baseT) transformers, there's a possibility that one bridges two POE
(power over Ethernet) poles with a receiver transformer. Compliant POE sources, though, shut
down if there's a short, so it shouldn't harm anything.

If the experimenter used a simple voltmeter, he could see power presence, and (if he also tested
the resistance) would know which wires went together in pairs. Then, there's two polarities in
each pair, and swapping pairs, so that's eight possibilities. Without probing, there'd be 4*3*2 = 12

Comment: Re: TCO (Score 1) 341

Sorry, thats a load of bollocks - the NHS has had over half a decade to do something about their situation and they failed...
UK law requires that a purchase be fit for a reasonable period of time (depending on the item involved, but the maximum time is typically six years), and XP is well past that test...

The government is to blame here, not Microsoft, so its only right that the government pay the fine, not Microsoft.

That's a bit too strong, surely! The NHS is intended to serve health care, and they HAVEN'T failed.

The 'reasonable period of time' argument does hold some water, and of course the extension of
software support is worth paying for. But, don't try to set a maximum time of six years! No
major project (road, hydrolectric dam, harbor) is ever funded on such a short period,
and there's no reason to stick such a software expiration date into every system that relies on software!

Microsoft has decided, for marketing reasons, to kill off XP software maintenance. Third party replacement
is difficult, or impossible, or more costly than buying a new version. Big customers can and should
fight for any modifications of the 'deadline for support' that they deem appropriate. Kudos to NHS!

Comment: Re:Solution... (Score 1) 167

by whit3 (#46494713) Attached to: Forests Around Chernobyl Aren't Decaying Properly

I would have thought that the fact that the experiments with leaves brought there from elsewhere decaying slower demonstrate that merely bringing foreign organisms (the collected leaves are not sterile, of course) is not going to help.

It's a full set of organisms you need; if, for instance, the earthworms were missing, a few strips of sod (or waiting for 'foreign' worms to migrate in) would be effective, but a pile of leaves wouldn't.

Comment: Re:clear, but wrong (Score 1) 107

by whit3 (#45147859) Attached to: Extreme Complexity of Scientific Data Driving New Math Techniques

While there may be millions of possible reconstructions for a fuzzy, ill-defined image, the simplest (sparsest) version is probably the best fit."

Of the millions of possibilities, the sparsest is MOST likely. Perhaps it's twice as likely as any other possibility. That still means it's 99.999% likely to be wrong

I interpreted this to be a description of maximum-entropy filtering (i.e. making an output image with least information, consistent with input image with sparse information content overlaid with full-textured noise.)
It certainly works for (for example) starfields seen in a badly focused telescope; NASA used this for Hubble reconstructions.
Every possible reconstruction will have some 'wrong' content, because noise is guaranteed (if only by the quantum uncertainty principle). That doesn't make the maximum-entropy filter useless, it just means the utility depends on the subject's compliance with the minimum-information assumption.

Comment: Re:Best solution? (Score 4, Insightful) 225

by whit3 (#44752469) Attached to: Japanese Ice Wall To Stop Reactor Leaks

Frozen ground is only waterproof if there are no holes. Frost heaves tend to break up the ground and make holes.

Actually, a frozen region in the soil is a good container, because water that starts to
  leak through... freezes solid and plugs the leak.

Frost heave is caused by thermal gradient, and
transports water to the coldest spot (which is
the container wall, safely underground) then freezes it.
So, no problem there!

Comment: Re:"Enable"? (Score 1) 102

Any cast metal needs machining afterwards, even if it's just to clean up the sprue area and to cut screw threads. Difficulties in casting are not why we don't see conventional metals used ...

Yes, and no: most cast metal shrinks markedly when it cools, so there's an oversize pattern (two percent for iron) used in making the mold. Amorphous metal has almost the same density when it's cool, it shrinks only slightly (an order of magnitude less shrinkage).

When you don't know what to do, walk fast and look worried.