True, but only in the case of huge files that require no disk access to generate dynamically.
Except that the database entries used are more likely to be reused for other requests -- so if the output could be cached, the database certainly would be.
Obviously, in some cases it is better to precompute entire pages; but it is really something which has to be determined on a case-by-case basis.
Even C cannot dynamically generate a file as fast as it can be read from disk.
That depends upon what the file is, and how fast your disk system is. Many large scientific computations which, in the past, precomputed values and stored them to disk now recompute as necessary, simply because the recomputation is faster than a disk access.
You won't be able to regenerate a file as fast as it can be read from cache; but unless you have an infinite amount of cache memory, there are likely to be cases where you're better off to recompute and allow something else to be cached.
What's the point behind having bunkers here which can withstand nuclear attacks?
The obvious answer would be that they wanted to ensure that the communications infrastructure would survive, but that doesn't make sense -- the towers would be destroyed quite easily, and without the towers, all the equipment protected in the bunkers would be useless anyway.
Anyone want to suggest changes to TCP/IP that would allow you to handle when acks arrived before the message they acknowledge has been sent? Just asking.
Sure: If you receive an ACK to a packet you haven't sent, put it into a buffer. Each time you're about to send a packet, check to see if you've already received an ACK for it. If you have, adjust the window as apppropriate and don't send the packet.
An increase in data density automatically implies an increase in transfer rate
True.
An 80GB platter turning at 7200 RPM can be read twice as fast as a 40 GB platter also turning at 7200 RPM
False.
The areal density is increased by packing more bits per track and by packing tracks closer together. An 80GB platter will give you a raw data rate 42% higher than a 40GB platter, all else equal.
The title calls this a "tugboat", but as far as I can see from the article, it is really just an extra fuel tank and set of rockets.
A real tugboat would be very cool indeed -- something which could grab a satellite, move it up back into the correct orbit, and then let go and move on to the next satellite -- but it looks like this is rather less so.
Let's see... you have unexpected protection faults, you're running on antique hardware, and when you try the same code on a different machine, it works fine.
That sounds exactly like the symptoms of hardware which has exceeded its MTBF.
Ever seen the inside of a car impact test facility? [snip] I mention this as an example application where "bright flashes of light" (emphasis mine) aren't practical, so they have to go whole hog. Kinda cool.
Yes, there are always going to be exceptions. But you'll note that they don't have people inside those facilities when they have all the lights turned on.
I guess I should have said "you can't get high quality 10^6 fps video for more than a fraction of a second at a time unless you evacuate the area first".
Ok, I'll admit that I'm out by a factor of two on the CCD efficiency thing -- I wasn't sure how good they were, so I googled and took the first number which came out.
As for the number of photons: 8 bit grayscale usually means 64 (not 256!) distinguishable levels. That is, on the 0-255 scale, you'll usually be able to distinguish between a 100 and a 104. In order to resolve N different levels when you're receiving statistical inputs, you need N^2 data points, ie "white" would be at least 4096 photons. Because you want to have that same quality on each of the three colour planes, multiply by three.
The wavelength of visible light (in a vacuum) is between 4x10^(-7) and 7x10^(-7) m. The speed of light is 3x10^8 m/s (in a vacuum). Planck's constant is 6.6x10^(-34) J s.
Put these together, and a single photon of visible light has an energy of between 2.8x10^(-19) and 5x10^(-19) J.
Suppose you want to get 24-bit colour. As an absolute minimum, you'll want to be able to detect 4096 photons per colour per pixel per frame. CCDs are typically 50% efficient, which means you need 256*3*2 incoming photons per pixel. At, say, 1024x1024 pixels and a million frames per second, that means 3*4096*2*1024*1024*1000000 = 2.6x10^16 photons per second, at an average energy of 3.9x10^(-19) J each.
That's an absolute minimum of 1.0x10^(-2) W of incoming radiation.
How much light is available? Well, at "bright sunlight" is approximately 30 W/m^2 of visible light.
That means that you'd need an aperture roughly 28mm across... which isn't impossible, but is certainly not going to be desireable.
So how does ultra-fast photography work? They use really bright flashes of light... which is why you don't want to be filmed for more than a fraction of a second at once.
Re:They're running out of book topics
on
Vi IMproved -- Vim
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· Score: 1
" Hartswick said Linux was evaluated against a Windows-based system and performed flawlessly for three months, whereas the Windows-based system failed after six or seven days. "
If you have to resort to saying "well, it's better than Windows", you've got problems.
Re:award winning, no less
on
Haiku vs Spam
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· Score: 2
It seems that you have five, seven, five, sir; but not a joke of nature
256 + 652 = 908 908 + 809 = 1717 1717 + 7171 = 8888, which is a palindrome.
However, 196 + 691 = 887 887 + 788 = 1675 1675 + 5761 = 7436 7436 + 6347 = 13783 and contining on for a few million digits still doesn't end up at a palindrome.
A few months ago, ESR gave a talk at the local computing department and told us that Big Unix died because it was closed source. When asked how he explained Microsoft's 20 years of success, he replied "Really good advertising?".
The same explains why MySQL is popular -- if you have good enough advertising, it doesn't matter what sort of crap you put out or how many better alternatives there are.
Ok, so they have a piece of paper. Who cares? It isn't going to do them any good.
There is a huge volume of prior art. If they sue anyone over this, they'll be laughed out of court -- and probably be required to pay the defendant's legal fees as well.
People complain about how easy it is to get patents, but they're missing a major point: The USPTO could just stamp "APPROVED, $DATE" on every piece of paper which comes through the door and invalid patents would be just as invalid as they ever were.
Linus didn't endorse one platform or the other, he only explained that if Hammer was to become dominant instead of Itanium, it would save the kernel developers problems solving the Itanium paging problems.
I think you mean linux's paging problems. Specifically, the fact that gcc being broken means that linux uses 32 bits for fields which should be 64 bits.
Slashdot Mirror
True, but only in the case of huge files that require no disk access to generate dynamically.
Except that the database entries used are more likely to be reused for other requests -- so if the output could be cached, the database certainly would be.
Obviously, in some cases it is better to precompute entire pages; but it is really something which has to be determined on a case-by-case basis.
Even C cannot dynamically generate a file as fast as it can be read from disk.
That depends upon what the file is, and how fast your disk system is. Many large scientific computations which, in the past, precomputed values and stored them to disk now recompute as necessary, simply because the recomputation is faster than a disk access.
You won't be able to regenerate a file as fast as it can be read from cache; but unless you have an infinite amount of cache memory, there are likely to be cases where you're better off to recompute and allow something else to be cached.
Google has a few of the pictures here.
What's the point behind having bunkers here which can withstand nuclear attacks?
The obvious answer would be that they wanted to ensure that the communications infrastructure would survive, but that doesn't make sense -- the towers would be destroyed quite easily, and without the towers, all the equipment protected in the bunkers would be useless anyway.
Am I missing something here?
Maxtor has once again shown the world that we need more room for porn
Shouldn't that be "Maxtor has once again shown the world that we need more porn in order to fill the available space"?
Anyone want to suggest changes to TCP/IP that would allow you to handle when acks arrived before the message they acknowledge has been sent? Just asking.
Sure: If you receive an ACK to a packet you haven't sent, put it into a buffer. Each time you're about to send a packet, check to see if you've already received an ACK for it. If you have, adjust the window as apppropriate and don't send the packet.
Scottland tried it too, but when they got near windy spots to start construction, the wind kept lifting up their kilts Marlyn-Monroe-style.
Not quite: Marilyn Monroe didn't wear traditional Scottish undergarments.
The 42% came from thinking sqrt(2)-1. No, I don't know how I managed to misremember the decimal expansion of sqrt(2).
An increase in data density automatically implies an increase in transfer rate
True.
An 80GB platter turning at 7200 RPM can be read twice as fast as a 40 GB platter also turning at 7200 RPM
False.
The areal density is increased by packing more bits per track and by packing tracks closer together. An 80GB platter will give you a raw data rate 42% higher than a 40GB platter, all else equal.
The title calls this a "tugboat", but as far as I can see from the article, it is really just an extra fuel tank and set of rockets.
A real tugboat would be very cool indeed -- something which could grab a satellite, move it up back into the correct orbit, and then let go and move on to the next satellite -- but it looks like this is rather less so.
You were wrong even before this announcement. 2TB RAID arrays have been practical for quite a while.
Let's see... you have unexpected protection faults, you're running on antique hardware, and when you try the same code on a different machine, it works fine.
That sounds exactly like the symptoms of hardware which has exceeded its MTBF.
Ever seen the inside of a car impact test facility? [snip] I mention this as an example application where "bright flashes of light" (emphasis mine) aren't practical, so they have to go whole hog. Kinda cool.
Yes, there are always going to be exceptions. But you'll note that they don't have people inside those facilities when they have all the lights turned on.
I guess I should have said "you can't get high quality 10^6 fps video for more than a fraction of a second at a time unless you evacuate the area first".
Ok, I'll admit that I'm out by a factor of two on the CCD efficiency thing -- I wasn't sure how good they were, so I googled and took the first number which came out.
As for the number of photons: 8 bit grayscale usually means 64 (not 256!) distinguishable levels. That is, on the 0-255 scale, you'll usually be able to distinguish between a 100 and a 104. In order to resolve N different levels when you're receiving statistical inputs, you need N^2 data points, ie "white" would be at least 4096 photons. Because you want to have that same quality on each of the three colour planes, multiply by three.
Let's do some arithmetic:
The wavelength of visible light (in a vacuum) is between 4x10^(-7) and 7x10^(-7) m.
The speed of light is 3x10^8 m/s (in a vacuum). Planck's constant is 6.6x10^(-34) J s.
Put these together, and a single photon of visible light has an energy of between 2.8x10^(-19) and 5x10^(-19) J.
Suppose you want to get 24-bit colour. As an absolute minimum, you'll want to be able to detect 4096 photons per colour per pixel per frame. CCDs are typically 50% efficient, which means you need 256*3*2 incoming photons per pixel. At, say, 1024x1024 pixels and a million frames per second, that means 3*4096*2*1024*1024*1000000 = 2.6x10^16 photons per second, at an average energy of 3.9x10^(-19) J each.
That's an absolute minimum of 1.0x10^(-2) W of incoming radiation.
How much light is available? Well, at "bright sunlight" is approximately 30 W/m^2 of visible light.
That means that you'd need an aperture roughly 28mm across... which isn't impossible, but is certainly not going to be desireable.
So how does ultra-fast photography work? They use really bright flashes of light... which is why you don't want to be filmed for more than a fraction of a second at once.
Next: ls for dummies
No, that would have to be "LiSt files -- ls".
" Hartswick said Linux was evaluated against a Windows-based system and performed flawlessly for three months, whereas the Windows-based system failed after six or seven days. "
If you have to resort to saying "well, it's better than Windows", you've got problems.
It seems that you have
five, seven, five, sir; but not
a joke of nature
Using floating-point luminosity values eliminates a variety of clipping artifacts which otherwise appear close to light sources.
I imagine there may be more palidromes in a base two system, vs, say, a base 666 system. (to choose an arbitrary base).
No. In any base, the number of palindromes less than n is O(n^(1/2)).
I posted a story a week ago about the prime number problem being solved for the first time with a deterministic algorithm and it was rejected by /.
You aren't talking about this by any chance, are you?
256 + 652 = 908
908 + 809 = 1717
1717 + 7171 = 8888, which is a palindrome.
However,
196 + 691 = 887
887 + 788 = 1675
1675 + 5761 = 7436
7436 + 6347 = 13783
and contining on for a few million digits still doesn't end up at a palindrome.
A few months ago, ESR gave a talk at the local computing department and told us that Big Unix died because it was closed source. When asked how he explained Microsoft's 20 years of success, he replied "Really good advertising?".
The same explains why MySQL is popular -- if you have good enough advertising, it doesn't matter what sort of crap you put out or how many better alternatives there are.
Ok, so they have a piece of paper. Who cares? It isn't going to do them any good.
There is a huge volume of prior art. If they sue anyone over this, they'll be laughed out of court -- and probably be required to pay the defendant's legal fees as well.
People complain about how easy it is to get patents, but they're missing a major point: The USPTO could just stamp "APPROVED, $DATE" on every piece of paper which comes through the door and invalid patents would be just as invalid as they ever were.
Linus didn't endorse one platform or the other, he only explained that if Hammer was to become dominant instead of Itanium, it would save the kernel developers problems solving the Itanium paging problems.
I think you mean linux's paging problems. Specifically, the fact that gcc being broken means that linux uses 32 bits for fields which should be 64 bits.