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Bjarne Stroustrup Awarded 2015 Dahl-Nygaard Prize

whoisisis Re:Is FORTRAN still winning? Was Re:Poor Alan Kay (200 comments)

Repeatedly allocating and deallocating can give a huge performance hit, so I tend to do all my allocations before the main loop.

which is the correct way of doing it. Allocating and deallocating, especially larger chunks of memory, requires you to interact with the operating system.
This should off course be avoided in tight loops.

about a week ago
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Bjarne Stroustrup Awarded 2015 Dahl-Nygaard Prize

whoisisis Re:Is FORTRAN still winning? Was Re:Poor Alan Kay (200 comments)

I've been writing a scientific simulation in Fortran for half a year now. I usually like to write in some combination of C and Python.

While Fortran does make the life of a compiler writer easier, I think C benefits from being a small and very popular language.
C compilers are just more advanced, which gives it the speed advantage. But the speed difference for most purposes is negligible.
Choosing the right algorithm and approximations is a much more important concern (factors of 10-100-1000 vs. 1.1-1.2-1.3).
Dynamic memory management is not much different from C.

In my experience, Fortran is extremely useful for expressing linear algebra, which is heavily used in quantum mechanics.
At least it is much much better than C. So in terms of programmer efficiency in scientific calculations, I think Fortran beats C by quite a margin.

Fortran sucks at pretty much anything else though. For example, I think it's a lot easier to have a config module (e.g. class) to manage simulation parameters and recompile the whole application every time you change settings than it is to use an actual configuration file.

The next time I write a scientific application, I think I will have Python handle the logistics (parallelization, files, user input, etc.) and let Fortran do the (heavy) computations.

about a week ago
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My toy collection is ...

whoisisis Re: toy collection (209 comments)

The only difference between boys and men is the price of their toys.

I never stopped having toys. My current favourite toy is a femtosecond laser system ;-)

about 4 months ago
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Ask Slashdot: How To Pick Up Astronomy and Physics As an Adult?

whoisisis Re:Has anyone done this? (234 comments)

I didn't but one of my friends did. He is some 15 years older than me, and was working as an electrician. On top of that, he is dyslexic.
We both study physics now. He's soon finished with his masters degree. I started right after high school, and I'm currently doing a phd.

about 4 months ago
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Ask Slashdot: How To Pick Up Astronomy and Physics As an Adult?

whoisisis RE: howto (234 comments)

I am a phd student in physics. I started the same year as an electrician about your age. I'm not sure if he quit his job or went down in time.
But he manages very well.

He's only a few years behind me, and about to finish his masters degree. He's even dyslexic, so I'm quite impressed by him.

about 4 months ago
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My cumulative GPA, thus far:

whoisisis Danish GPA (441 comments)

My GPA is way more than 4. It probably has something to do with the fact that in Denmark, the scale goes from -3 to 12.

about 2 years ago
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Electrical Grid Hum Used To Time Locate Any Digital Recording

whoisisis This could get messy (168 comments)

So now what the bad guys have to to after tampering with audio recordings is to subtract the hum of the mains and add the hum at a different time. ?

more than 2 years ago
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Gamma-Ray Photon Observations Indicate Space-Time Is Smooth

whoisisis Re:Space/time duration/distance (81 comments)

Seven billion light years away (seven billion years ago)

I may not have this right, but due to the expansion of space, wouldn't it have been closer than seven billion light years away at the time of the kaboom? And if the light's taken seven billion light years to get here, space will have expanded further, so the remnants would now be further than seven billion light years away. Right?

Or is this the sort of thing where you can be specific about the distance, or the time, but not both?

Wikipedia has an answer, but I think the above is just meant to give the layman some rough understanding of what's going on.

Beware that it is extremely difficult to measure these kinds of distances exactly. The figure may be a few orders of magnitude wrong, so whether you take into account the expanding universe or not may not be that important...
Cosmologists measure everything in gigaparsec. 7b light years is only 0.3 GPc so it may not be that important.

about 2 years ago
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% of my digital storage that is solid-state:

whoisisis Re:100% solid state. (280 comments)

Because i don't know any storage media that's in liquid or gaseous form, or a plasma.

I, for one, store all my digital stuff in the Bose-Einstein condensate phase of matter on my shiny new quantum computer

more than 2 years ago
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Nmap 6 Released Featuring Improved Scripting, Full IPv6 Support

whoisisis Re:Better Details (45 comments)

I find it a bit amusing that their IPv6 address starts with 2600

more than 2 years ago
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Stealing Smartphone Crypto Keys Using Radio Waves

whoisisis TEMPEST (37 comments)

Looks like they need some TEMPEST shielding.

about 3 years ago
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IBM Shrinks Bit Size To 12 Atoms

whoisisis Re:256 qbit per atom? (135 comments)

See also Phys. Rev. A 78, 012336 (2008) http://pra.aps.org/abstract/PRA/v78/i1/e012336. With Holmium they get 60 qbits per atom from these "pooled states".

The articles are slightly old. K. Mølmer said during a lecture some time ago that they have found an atom suitable for 128 or 256 qbits with this method.

about 3 years ago
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IBM Shrinks Bit Size To 12 Atoms

whoisisis Re:256 qbit per atom? (135 comments)

Not exactly. They have quite some clever ways to handle these Rydberg states in neutral atoms. They use hyperfine splitting to get a large amount of qbits in single atoms.

See Rev. Mod. Phys. 82, 2313–2363 (2010) (http://rmp.aps.org/abstract/RMP/v82/i3/p2313_1)

about 3 years ago
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IBM Shrinks Bit Size To 12 Atoms

whoisisis Re:1/12 bit per atom? Not impressed. (135 comments)

I think they used one or a few electrons in iron or nickle. An electron can be in any number of excited states.

about 3 years ago
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IBM Shrinks Bit Size To 12 Atoms

whoisisis 1/12 bit per atom? Not impressed. (135 comments)

I've seen researchers at our university create 256 qbits in a single atom. Of course, qbits are not directly usable in conventional computing...

about 3 years ago
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North Korean Dictator Kim Jong Il Dead at 70

whoisisis News for nerds (518 comments)

How does this qualify as "News for nerds, stuff that matters"?

more than 3 years ago
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Smallest Known Black Hole Found

whoisisis Re:interesting, but vaguely in line with estimates (69 comments)

I am a physicist, although not an astronomer. Indeed, microscopic black holes (less than the earth mass) are speculated to exist. They're called primordial black holes and must be created in the early universe.

They're candidates for the sources of gamma ray bursts.

more than 3 years ago
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Ask Slashdot: Is Your Data Safe In the Cloud?

whoisisis Encrypt your data (332 comments)

Well, I trust both Google and Dropbox enough to store my encrypted backups. Wouldn't upload anything important without encryption though.

more than 3 years ago
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Ask Slashdot: Best Flash-Friendly Router To Replace Aging WRT54GS?

whoisisis tp-link wr1043 (334 comments)

I run OpenWRT Backfire on my TP-link WR1043. It even comes with an USB port.
It's MIPS based, comes with 32 MB ram and a gigabit switch etc.

Can only recommend.

more than 3 years ago
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Physicist Uses Laser Light As Fast, True-Random Number Generator

whoisisis Re:"Truly random numbers" (326 comments)

Well, something has to explain what we observe in the lab.
So far, quantum physics is the only successful theory.

more than 3 years ago

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