The main problem with shared memory between processes compared to using shared globals between threads is
1)with shared memory you need to specifically create it which requires finding unique keys that don't clash with
anything else - not a big deal but extra hassle nonetheless 2)unless you want to create little bits of shared memory all over the place (eg 4 byte integer sizes) to emulate normal variables you'll have one big block of the stuff. And with one big block you have to make damn sure you get your demarcation right and you don't have processes writing to or reading from sections they shouldn't. This of course is in the same problem realm as buffer overflow issues with arrays 3) shared memory has no intrinsic locking abilities unlike posix threads (unless you set aside certain bits to be read/write flags). This means you have to *spit gag* use SysV semaphores. A more counterintuitive API I yet to have the misfortune to use. Whoever designed it should be shot.
Also , fork() can be quite expensive. Not a problem if the process you're firing off will be running for hours but it is an issue if the process simply (lets use Apache as an example) reads from a socket , spits some data back down then quits.
In general I myself would use multiprocess instead of multithread but not always.
"To live, you need a ppO2 within a certain range. IIRC, between about 0.05 (5% at 1 atm, or 10% at 0.5 atm, etc.) and 2.4 (pure O2 at 2.4 atm, or 50% at 4.8 atm, etc.)."
So reading this right , this means the lowest pressure any human could survive in would be 0.05 Atm with 100% O2 (other pressure related issues notwithstanding). So that means no one will be walking out on the surface of Mars (0.006 Atm) anytime soon even with a pure O2 supply shoved right up their noses. Oh well...
You're thinking of nitrogen narcosis and it only happens at high pressure such as when scuba diving. It DOES NOT happen at normal atmospheric pressure.
Piracy of DVDs and CDs is flourishing there. Most people don't even have a computer , never mind an internet connection and if you go down the local markets you will find tons of pirated material (most of it done badly it must be said). Its about time people in IT whether media types or coders really wrenched themselves out of this western mindset where they seem to believe that because they have broadband and a flash PC then the whole world does.
Newsflash: most of the people in the world don't even own a radio never mind a computer.
Oh wait , those morons wouldn't know what FTP or SMB were and that fact it and other general peer to peer file sharing methods have been around for decades if the facts were stamped on their sloping foreheads in glowing green ink. I truly despair of politicians and it frightens me that these morons have public mandates.
Don't they just. Just like most return-to-basic cults they're nothing but a bunch of hypocrites. They disdain and ignore the modern world - oh , until they really need it , then its different. They should put their lives where their mouths are and cut themselves off completely. Got cancer Mr Amish? Tough. You don't like the modern world so you won't like modern treatments - get lost and go chew some herbs.
Quite. Sounds to me all he does is run a bog standard computer admin course which can be found in their multitudes in any 2 bit college prospectus. As a lecturer he should know better than to make generalisations about one aspect of a subject based on another.
"'m certainly not playing the one-upmanship card "
You should. Leicester Poly was the place you went in the east midlands if you couldn't get into Loughborough or Nottingham unis. Its always been 2nd division and nothing has changed.
No it isn't. Someone has to write the from-scratch stuff , it doesn't write itself. Just because you never never go lower than legolibfordummies.dll doesn't mean others don't.
"For instance nobody codes their own c/c++ program that listen to http requests"
Says who? I've seen it in a firm I worked for where they wanted web functionality attached to a process in a large system and it was simpler to add in web functionality that fart about setting up an entire web server and the IPC links to it. Besides , any competant C/C++ coder should be able to write an HTTP parser from scratch in 2 or 3 days.
Can you image if he gets a mail from Guinness saying "Sorry , you missed the record by 10. Or at least we think you did but tape 26 got chewed by the machine at digit 54166. Bad luck son, try again next year and next time use Memorex!"
>Believe me that after a short while you will be freezing in space
Depends on how fast the human body radiates heat in a vacuum. Has anyone ever measured it? I would imagine it would be the same as standing in a breeze with air at body temperature so it takes away any heat you generate but at the same time doesn't start to cool you down nor does it heat you up.
Radioactivity can cause glowing on its own. Cherenkov (sp?) radiation is the blue glow seen around spent nuclear fuel rods in water storage facilities and its caused by neutrons breaking the speed of light *in water* and causing a shock wave thats seen in the visible part of the EM spectrum.
I often wondered whether if you were in a vacuum you might even overheat? Since theres no air convection taking heat away from your body and any sweat would immediately vapourise as it came out your pores so it wouldn't have a chance to spread over your skin and cool you.
>Kerberos/LDAP integration: If you don't know, this is what will enable SSO capabilities. (aka, what windows did with AD over 7 years ago.)
I think you need to learn your IT history a bit better. Unix has had single sign on capability since NIS (formerly Yellow Pages) was created back in the 80s (I believe version 2 was 1985) and linux has had it since pretty early on in its history. As usual Microsoft were last out of the stalls but made a big song and dance about it and pretended they'd re-invented the wheel yet again.
And what happens if someone if one country/state wants to connect to an NTP server in another? If that NTP server only gives its local time then that computer will get the wrong time and if it gives all timezone times then not only will it send FAR more data but you'll STILL have to set the timezone in your machine anyway so it can select the correct one from NTP.
So I'm afraid your idea is a non starter.
Re:Because some people don't want an all-in-one
on
DIY Laptop
·
· Score: 1
Well in that case I'm not sure what his issue is since if a device can be mounted as a standard USB file system (and every digital camera I've used can and so can most mp3 players - phones are another matter) then things are more convergent than he assumes.
Because some people don't want an all-in-one
on
DIY Laptop
·
· Score: 1
All-in-one devices have been around for years in various forms. And you know what? They almost all suck. Theres no point in something being able to do 10 things if it does most or all of them badly. When I buy a camera I want a camera. I DONT want a camera come phone come mp3 player come something else. I want to know its been designed from the ground up as a camera and will do that job the best it can and isn't just "a computer with a lens.".
Also if you're all-in-one super device breaks then you've lost everything in one go.
Quite. These guys might know information storage retrieval theory but they seem to know jack sh1t about natural selection. Perhaps they're based in Texas?:)
Seems to me this is a 3rd rate solution looking for a problem anyway not to mention the fact that since DNA used base 4 why store the data in binary base 2? You're wasting 75% of the storage ability.
Point is , no one really understands why sometimes light acts as a wave and sometimes as a particle. But that lack of understanding doesn't prevent us using and basing theories on light. Similarly just because some jackass wont' accept the huge amount of fossile and genetic evidence for evolution (what do they want, a fast forward of the whole of time on a TV screen to prove to them it happens?) doesn't mean we shouldn't use the theory.
Perhaps we should only ever use 100% known facts in science then? So thats a lot of particle physics and cosmology out the window (how do you 100% prove black holes exist?) then , we won't teach that to kids since it can't be proven to your liking. Electromagnetism? Well we have theories of what light actually is but none of it has been proven since the theories (particle vs waves) contradict. So can't use that in any scientific papers.
Whats that you say? Theres plenty of evidence for all of the above? Yes , but its not 100% conclusive proof which you obviously want, though personally I'd be quite happy with the 90% proof (IMO) that evolution has.
Alternatively perhaps we should just believe in some invisible friend in the sky and lots of conjuring tricks from millenia ago. Yes , thats the way forward , I'm sure that'll be a success in advancing science.
I await the negative mod points from the bible bashers.
You can use shared memory between processes in the same way that you'd use shared global/static variables between threads , so in that sense its fairly simple. Though of course you'd have to use some sort of signalling mechnism on top or just a polling loop on the memory (very wasteful). BUT , if you have an VERY complicated application its usually best to leave threads alone as they in my experience at best double the complexity of the program and at worst,well , its anyones guess - I've spent literally days trying to find race condition bugs with threads and its not funny.
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The main problem with shared memory between processes compared to using shared globals between threads is
1)with shared memory you need to specifically create it which requires finding unique keys that don't clash with
anything else - not a big deal but extra hassle nonetheless
2)unless you want to create little bits of shared memory all over the place (eg 4 byte integer sizes) to emulate normal
variables you'll have one big block of the stuff. And with one big block you have to make damn sure you get your demarcation right and you don't have processes writing to or reading from sections they shouldn't. This of course is in the same problem realm as buffer overflow issues with arrays
3) shared memory has no intrinsic locking abilities unlike posix threads (unless you set aside certain bits to be read/write flags). This means you have to *spit gag* use SysV semaphores. A more counterintuitive API I yet to have the misfortune to use. Whoever designed it should be shot.
Also , fork() can be quite expensive. Not a problem if the process you're firing off will be running for hours but it is an issue if the process simply (lets use Apache as an example) reads from a socket , spits some data back down then quits.
In general I myself would use multiprocess instead of multithread but not always.
"To live, you need a ppO2 within a certain range. IIRC, between about 0.05 (5% at 1 atm, or 10% at 0.5 atm, etc.) and 2.4 (pure O2 at 2.4 atm, or 50% at 4.8 atm, etc.)."
So reading this right , this means the lowest pressure any human could survive in would be 0.05 Atm with 100% O2 (other pressure related issues notwithstanding). So that means no one will be walking out on the surface of Mars (0.006 Atm) anytime soon even with a pure O2 supply shoved right up their noses. Oh well...
"but 19% O2 is still right on lower limit of breathable air for most people"
Rubbish.
"hat can lead to pulmonary edema, cerebral edema, and some other nasty symptoms"
Those are caused by low atmospheric pressure , not low O2 levels. The pressure in this system will be the same as outside.
You're thinking of nitrogen narcosis and it only happens at high pressure such as when scuba diving. It DOES NOT happen at normal atmospheric pressure.
Piracy of DVDs and CDs is flourishing there. Most people don't even have a computer , never mind an internet connection and if you go down the local markets you will find tons of pirated material (most of it done badly it must be said). Its about time people in IT whether media types or coders really wrenched themselves out of this western mindset where they seem to believe that because they have broadband and a flash PC then the whole world does.
Newsflash: most of the people in the world don't even own a radio never mind a computer.
Oh wait , those morons wouldn't know what FTP or SMB were and that fact it and other general peer to peer file sharing methods have been around for decades if the facts were stamped on their sloping foreheads in glowing green ink. I truly despair of politicians and it frightens me that these morons have public mandates.
>The Amish do see modern doctors when necessary.
Don't they just. Just like most return-to-basic cults they're nothing but a bunch of hypocrites. They disdain and ignore the modern world - oh , until they really need it , then its different. They should put their lives where their mouths are and cut themselves off completely. Got cancer Mr Amish? Tough. You don't like the modern world so you won't like modern treatments - get lost and go chew some herbs.
"ie. not Computer Science."
Quite. Sounds to me all he does is run a bog standard computer admin course which can be found in their multitudes in any 2 bit college prospectus. As a lecturer he should know better than to make generalisations about one aspect of a subject based on another.
"'m certainly not playing the one-upmanship card "
You should. Leicester Poly was the place you went in the east midlands if you couldn't get into Loughborough or Nottingham unis. Its always been 2nd division and nothing has changed.
"This is always true, "
No it isn't. Someone has to write the from-scratch stuff , it doesn't write itself. Just because you never never go lower than legolibfordummies.dll doesn't mean others don't.
"For instance nobody codes their own c/c++ program that listen to http requests"
Says who? I've seen it in a firm I worked for where they wanted web functionality attached to a process in a large system and it was simpler to add in web functionality that fart about setting up an entire web server and the IPC links to it. Besides , any competant C/C++ coder should be able to write an HTTP parser from scratch in 2 or 3 days.
Can you image if he gets a mail from Guinness saying "Sorry , you missed the record by 10. Or at least we think you did but tape 26 got chewed by the machine at digit 54166. Bad luck son, try again next year and next time use Memorex!"
One would expect being able to decode the image to be a fundamental part of any image read/writer.
Or perhaps I'm just old fashioned...
"Takes all of a couple of days of dev time to integrate libtiff with all the available codecs into a typical app."
Oh is that all.
Jeez , I wonder what palnet some people live on , I really do...
>Believe me that after a short while you will be freezing in space
Depends on how fast the human body radiates heat in a vacuum. Has anyone ever measured it? I would imagine it would be the same as standing in a breeze with air at body temperature so it takes away any heat you generate but at the same time doesn't start to cool you down nor does it heat you up.
Radioactivity can cause glowing on its own. Cherenkov (sp?) radiation is the blue glow seen around spent nuclear fuel rods in water storage facilities and its caused by neutrons breaking the speed of light *in water* and causing a shock wave thats seen in the visible part of the EM spectrum.
I often wondered whether if you were in a vacuum you might even overheat? Since theres no air convection taking heat away from your body and any sweat would immediately vapourise as it came out your pores so it wouldn't have a chance to spread over your skin and cool you.
>Kerberos/LDAP integration: If you don't know, this is what will enable SSO capabilities. (aka, what windows did with AD over 7 years ago.)
I think you need to learn your IT history a bit better. Unix has had single sign on capability since NIS (formerly Yellow Pages) was created back in the 80s (I believe version 2 was 1985) and linux has had it since pretty early on in its history. As usual Microsoft were last out of the stalls but made a big song and dance about it and pretended they'd re-invented the wheel yet again.
And what happens if someone if one country/state wants to connect to an NTP server in another? If that NTP server only gives its local time then that computer will get the wrong time and if it gives all timezone times then not only will it send FAR more data but you'll STILL have to set the timezone in your machine anyway so it can select the correct one from NTP.
So I'm afraid your idea is a non starter.
Well in that case I'm not sure what his issue is since if a device can be mounted as a standard USB file system (and every digital camera I've used can and so can most mp3 players - phones are another matter) then things are more convergent than he assumes.
All-in-one devices have been around for years in various forms. And you know what? They almost all suck. Theres no point in something being able to do 10 things if it does most or all of them badly. When I buy a camera I want a camera. I DONT want a camera come phone come mp3 player come something else. I want to know its been designed from the ground up as a camera and will do that job the best it can and isn't just "a computer with a lens.".
Also if you're all-in-one super device breaks then you've lost everything in one go.
No thanks, give me dedicated devices anyday.
"it goes around the Sun Earth barycenter."
Which happens to be so close to the centre of the sun that it makes no difference.
Quite. These guys might know information storage retrieval theory but they seem to know jack sh1t about natural selection. Perhaps they're based in Texas? :)
Seems to me this is a 3rd rate solution looking for a problem anyway not to mention the fact that since DNA used base 4 why store the data in binary base 2? You're wasting 75% of the storage ability.
Point is , no one really understands why sometimes light acts as a wave and sometimes as a particle. But that lack of understanding doesn't prevent us using and basing theories on light. Similarly just because some jackass wont' accept the huge amount of fossile and genetic evidence for evolution (what do they want, a fast forward of the whole of time on a TV screen to prove to them it happens?) doesn't mean we shouldn't use the theory.
Perhaps we should only ever use 100% known facts in science then? So thats a lot of particle physics and cosmology out the window (how do you 100% prove black holes exist?) then , we won't teach that to kids since it can't be proven to your liking. Electromagnetism? Well we have theories of what light actually is but none of it has been proven since the theories (particle vs waves) contradict. So can't use that in any scientific papers.
Whats that you say? Theres plenty of evidence for all of the above? Yes , but its not 100% conclusive proof which you obviously want, though personally I'd be quite happy with the 90% proof (IMO) that evolution has.
Alternatively perhaps we should just believe in some invisible friend in the sky and lots of conjuring tricks from millenia ago. Yes , thats the way forward , I'm sure that'll be a success in advancing science.
I await the negative mod points from the bible bashers.
You can use shared memory between processes in the same way that you'd use shared global/static variables between threads , so in that sense its fairly simple. Though of course you'd have to use some sort of signalling mechnism on top or just a polling loop on the memory (very wasteful). BUT , if you have an VERY complicated application its usually best to leave threads alone as they in my experience at best double the complexity of the program and at worst ,well , its anyones guess - I've spent literally days trying to find race condition bugs with threads and its not funny.