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Comments

top

Can Wolfram Alpha Tell Which Team Will Win the Super Bowl?

leaen Re:No (126 comments)

Of course not. This is just as stupid as asking if you could calculate somebody's phone number.

Actually calculating phone numbers is simple, you just need to start from contradiction. You can derive anything from that including your mom's phone number. Its called principle of explosion.

about 7 months ago
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Why Standard Deviation Should Be Retired From Scientific Use

leaen Re:Issues (312 comments)

O(log(n)) for each and every insertion, yes... when you are doing n insertions, that becomes O(n log n). If you are trying to compute the mean deviation at every step as well, you are looking at O(n^2 log n),

No, you just failed data structure class. Insertion takes O(log(n)) with bookkeeping needed to find mean standard deviation in O(log(n)) time which gives a O(n log n) total time. All you need to know to calculate deviation is sum and number of elements above mean and sum of elements below mean. I explained it in more detail in parent post, there is standard data structure that can calculate sum of elements in of elements in given range in O(log(n)) time and supports insertion in O(log (n)) time.
A quick google query found following implementation: http://kaba.hilvi.org/pastel/pastel/sys/redblacktree.htm

because you cannot compute the mean deviation without revisiting *every* element you've collected so far, regardless of how they are stored or sorted.

Repeating a lie does not make it true.

about 8 months ago
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Why Standard Deviation Should Be Retired From Scientific Use

leaen Re:Issues (312 comments)

Collecting the data alone is a log(n) step... and can be worse if you are trying to keep the data sorted while you collect it.

Use red-black trees these keep data sorted with O(log(n)) worst case bound for insertion.

How can you calculate the mean deviation at any time without revisiting all of the data points that you have collected so far? How can you calculate do it in any time better than O(n)? Calculating standard deviation takes O(1) and does not require reexamining the data at all if you've been keeping track of right things during data collection (which still takes O(n)).

That is typical exam question for data structures class. You maintain a red-black tree and for node you keep a sum and count of elements of its subtree (you need to update these in rotation and thats it). As red-black tree has logarithmic height you easily find sum of elements greater than given number in logarithmic time. Just do binary search and sum values for subtrees whose smallest element is greater than searched element.
Once you have that a mean absolute difference by following expression
(sum_greater(mean) - count_greater(mean) * mean) + (count_less(mean) * mean - sum_less(mean))
and you can get each term in O(log (n)) time.

about 8 months ago
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Why Standard Deviation Should Be Retired From Scientific Use

leaen Re: Basic Statistics (312 comments)

Bzzt. Mathematically correct but practically wrong. Any real or simulated dataset from which you would want to compute a standard deviation will have the property that it will be a list of (most likely) double precision floating that is finite in size. This data defines a distribution that always has a finite first and second moment, so you will get a number that you can confidently call the standard deviation of the data. Even if it comes from physical process with a nonsense distribution like a Cauchy distribution, the standard deviation you compute will give you a bound on the spread of your data. If it's Gaussian, you can go back to your statistics class and say that 95% of the data will be within two SD's, etc. If it's not, you can use the Chebyshev rule (http://en.wikipedia.org/wiki/Chebyshev_inequality) to say that at least 75 percent of the data will be in two SD's, 89% will be within 3 SD's, etc, which is much coarser information, but is still reasonable to look at for worst-case analysis.

Yes but also useless when you have enough data to get reasonable mean estimate. You do not need Chebyshev inequality for getting confidence intervals, just compute appropriate 2.5percentile and 97.5percentile for 95% interval. By Glivenkoâ"Cantelli theorem these for measurable function converge regardless to distribution and are not sensitive to outliers.

about 8 months ago
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Why Standard Deviation Should Be Retired From Scientific Use

leaen Re:Issues (312 comments)

ncorrect... you need one pass to collect the data, and a second pass to compute the mean deviation. Both passes are O(n). You do not need to do a second pass to compute the standard deviation, it can be calculated in O(1) time based on data collected in the first pass. If you are only computing this once, doing two O(n)'s is just O(n), but if you are wanting to continually recalculate the mean as you add more elements to your data set, then the difference between them becomes much larger... mean deviation with data collection ends up being quadratic with the amount of data collected, while standard deviation with data collection remains linear with the amount of data collected.

Still incorrect, you need to know data structures for that. When you use a red-black tree where you in node maintain sum of element below node then you can compute sum of elements in arbitrary interval in O(log(n)) time. That cuts complexity from quadratic to O(n log n)

about 8 months ago
top

New Superconductor Theory May Revolutionize Electrical Engineering

leaen Re:Good Stuff (92 comments)

Well, superconductors killed my dad, so I'm looking for an immediate ban. If you don't like that, you can just say that directly to distraught face of my poor widowed mother. Superconductors also stole all of the insurance money and repeatedly raped my sister. Well, she called it rape, but really there was no resistance.

Sorry, we are superconductors. Resistance is futile.

about 9 months ago
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Ask Slashdot: Can You Trust Online Tax Software?

leaen Re:I Used a Popular Online Tax Service... (237 comments)

1. Buy a stock that you expect to decrease in value in the short term, but to make money in the long term. You pay, say, $10,000.

2. It drops to $5,000. Sell, you can mark off the $5,000 loss on your taxes.

3. Wait 30 days, then take that $5,000 and buy the same stock again. You can still take the $5,000 loss, but if (when) the stock finally appreciates, you make money there, too. :)

What about following plan.

1. Put $10000 in bank.

2. Wait 30 days, buy $7500 of stock and $2500 for taxes.

3. ???

4. Profit

about 10 months ago
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GCC 4.9 Coming With Big New Features

leaen Re:GCJ vs. JIT (181 comments)

P.S.: While I understand that much C/C++ syntax is driven by prior choices, much of this new syntax is UGLY. That's been a problem ever since templates started appearing, but it's gotten worse with every addition. At some point they need to do a de novo redefinition of syntax, and define an isomorphism between the two syntaxes. Then a compiler switch can alternate between syntaxes until the current version can be deprecated. I'm starting to think that APL had a better design than modern C++, and that was BAD. Now, in addition to > they've got [[ ]], and I guess next will be (( )) (unless that's already in use somewhere).

Yes, (( )) is used in attributes. Also ({ }) is used to convert compound statement into expression. You are left with {{ and {( and when these will be taken we start to use {) (}.

about 10 months ago
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Linux 3.13 Kernel To Bring Major Feature Improvements

leaen Re:So many improvements (190 comments)

You're obviously new to Slashdot. Slashdot may, at first glance, appear to be the intelligent and knowledgeable 0.01%, but it is really the idiotic 99.999999999999%

Note as there are 7 bilion people this means that everybody is on slashdot now.

about 10 months ago
top

Red Hat Releases Ceylon Language 1.0.0

leaen Re:Enough already. (159 comments)

There are to many programming languages.

We should write new one that to unite them all.

about 10 months ago
top

Crossing the Divide From Software Dev To Hardware Dev

leaen Re:Run! (105 comments)

Engineering isn't about proof, that's math. Engineering is about tolerances.

No engineering is about responsibility.
If you call yourself a engineer be prepared when somebody asks:
Who is responsible for this crap?

about a year ago
top

The Hail Mary Cloud and the Lessons Learned

leaen Re:Nothing you can do? (99 comments)

This is one reason why people recommend sudo instead of su. The admin logs in as himself and gains root privilege using his personal password. There is no shared root password, so you only have to disable the old admin's account and sudo access.

They recommend it as safer in theory.
In practice sudo is source of jokes like:
Q: H0w d0 I h4ck ubuntu?
A:
user
user
sudo
user

about a year ago
top

Utility Sets IT Department On Path To Self-destruction

leaen Re:Let me be 1 of the 1st here (478 comments)

Not necessarily: If it is domestic high-quality outsourcing, you know the people personally and there is a long-standing connection, it can work. But off-shoring basically never works and a cultural gap ensures that. Same wit off-shoring to China.

Quite the contrary, Chineese contractors are very intelligent. You can get a top talent from Chineese intelligence agency for cheap.

about a year ago
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Ask Slashdot: Are 'Rock Star' Developers a Necessity?

leaen Re:Relative (356 comments)

Heh, I spent a year cleaning up after the last "10x" developer. 10x the productivity, 10x the bugs.

Of course, his defect densitity is 10/10=1 which is a defect density of average programmer. So I hired him and you which saves us salary of 8 developers. Now get back to work.

-- your boss

1 year,6 days
top

Ballmer To Retire

leaen Re:In the next 12 months... (633 comments)

He can't even retire properly, should have done so years ago.

Newsflash. Hour ago boards of directors announced that he will be replaced by much more energetic person Stephen Elop.

1 year,26 days
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Ask Slashdot: Is Tech Talent More Important Than Skill?

leaen Re:Neither (277 comments)

I'm going with Coolidge on this one. "Nothing in the world can take the place of Persistence...

This is not true, to quote Kurt von Hammerstein:

I divide my officers into four groups. There are clever, diligent, stupid, and lazy officers. Usually two characteristics are combined. Some are clever and diligent -- their place is the General Staff. The next lot are stupid and lazy -- they make up 90 percent of every army and are suited to routine duties. Anyone who is both clever and lazy is qualified for the highest leadership duties, because he possesses the intellectual clarity and the composure necessary for difficult decisions. One must beware of anyone who is stupid and diligent -- he must not be entrusted with any responsibility because he will always cause only mischief.

I seen plenty of programmers that are persistent but their code is flawed on so many levels that if I wrote that code myself it would save me time over convincing managers that their code needs fixing and fixing it.

about a year ago
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SF Airport Officials Make Citizen Arrests of Internet Rideshare Drivers

leaen Re:Dispute - not often at all (510 comments)

How much would someone have benefited from having a car that cost 1/10th of what you paid but without many of those safety features? Someone then able to get to a job, who could then earn more, save more, and eventually afford a nice, safe car like yours. But now he can't, because the price of a car is too much.

That type of car is called motorcycle.

about a year ago
top

News Worth Buying On Paper

leaen Re:I'm still reading the paper on... paper (106 comments)

Either way, the younger generation isn't stupider than yours; it's just younger.

Badger jizz. I can do calculus, kinematics and statistics. My kids can barely count to twenty.

And how good you could do calculus when you were five?

about a year ago
top

Love and Hate For Java 8

leaen Re:Finally Fixing the Date stuff (434 comments)

why not

do {
foo();
bar();
} while (baz())

Am I missing something?

You missed ... Actually it continues with:

l4: if (baw()) goto l2;
...

With generic proof you can just append

else if (line==4) {
if (baw())
line=2;
else
line=5;
}

without resorting to ad-hoc constructs.

about a year ago
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Love and Hate For Java 8

leaen Re:Finally Fixing the Date stuff (434 comments)

find your gratuitous slur against "academic types" unwarranted and unfair. Academia has produced much innovation in programming. Do you forget the proof that Structured Programming is sufficient, and GOTOs are not necessary?

Nice now I can write

l1: foo();
l2: bar();
l3: if (baz()) goto l1;
...

as

line=1;
while (1) {
if (line==1) {
foo();
line=2;
}
else if (line==2) {
bar();
line=3;
}
else if (line==3) {
if (baz())
line=1;
else
line=4;
}
...

about a year ago

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