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.
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.
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.
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.
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.
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.
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)
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.
In wind power, yes, you use rare earth materials. But at end of life, these can be recycled. It's not like we throw the rare earth materials into space when we're done with them.
Solar power uses ground water in deserts. Does this even run out? I mean, ground water is there because it rains or comes in from the sea. Evaporating water from solar panels still make it into rain and so the cycle should continue.
When I started using Linux, I used WindowMaker as my window manager. It was a bit bloated, but it was fast and efficient. I soon switched to Fluxbox, since it is much nicer and easier to customize and it does not get in your way.
With Fluxbox, there is nothing (no icons, and no annoying screen-estate eaters or blinking distractions) but a single menu always/just one mouse click away/ with your most used applications in it. You don't even have to move your mouse and hit (or miss) an icon first. Desktop switching couldn't be faster, just press alt+fx or scroll with your mouse. No annoying or time consuming animations to distract or delay you.
I just encrypt my hard drive. If a thief nicks my laptop, all he's going to get is a piece of (old) hardware and a disk full of seemingly random numbers. While it's annoying, you don't need to put resources into tracking the bastard, just get on with it and buy a new machine, which you would anyway.
Hardware is cheap. Data is your time, work and money, so protect it with encryption and keep backups.
Slashdot Mirror
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.
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.
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.
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.
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. ?
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.
I find it a bit amusing that their IPv6 address starts with 2600
Looks like they need some TEMPEST shielding.
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.
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)
I think they used one or a few electrons in iron or nickle. An electron can be in any number of excited states.
I've seen researchers at our university create 256 qbits in a single atom. Of course, qbits are not directly usable in conventional computing...
How does this qualify as "News for nerds, stuff that matters"?
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.
Well, I trust both Google and Dropbox enough to store my encrypted backups. Wouldn't upload anything important without encryption though.
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.
Well, something has to explain what we observe in the lab.
So far, quantum physics is the only successful theory.
In wind power, yes, you use rare earth materials. But at end of life, these can be recycled. It's not like we throw
the rare earth materials into space when we're done with them.
Solar power uses ground water in deserts. Does this even run out? I mean, ground water is there because it rains or comes in from the sea.
Evaporating water from solar panels still make it into rain and so the cycle should continue.
What's the fuss?
or rather how it does so
I wonder if this chip can do plasticity and learning just as a real brain.
One thing is to hardwire a neural network, another is to mimic the brain.
The brain constantly rewires itself in different ways to learn.
I'm 23 too, and I use Fluxbox for the exact same reasons.
When I started using Linux, I used WindowMaker as my window manager. It was a bit bloated, but it was fast and efficient.
I soon switched to Fluxbox, since it is much nicer and easier to customize and it does not get in your way.
With Fluxbox, there is nothing (no icons, and no annoying screen-estate eaters or blinking distractions) but a single menu always /just one mouse click away/
with your most used applications in it. You don't even have to move your mouse and hit (or miss) an icon first.
Desktop switching couldn't be faster, just press alt+fx or scroll with your mouse.
No annoying or time consuming animations to distract or delay you.
I love Fluxbox!
Joseph Fourier made a scientific breakthrough quite late in his life (ca. 1820). We wouldn't be where we are today without his theories.
With encryption you don't even have to think about it. You can just forget you ever owned the computer.
I just encrypt my hard drive. If a thief nicks my laptop, all he's going to get is a piece of (old) hardware and a disk full of seemingly
random numbers. While it's annoying, you don't need to put resources into tracking the bastard, just get on
with it and buy a new machine, which you would anyway.
Hardware is cheap. Data is your time, work and money, so protect it with encryption and keep backups.