Ask Slashdot: What's the Most Often-Run Piece of Code -- Ever? 533
Hugo Villeneuve writes "What piece of code, in a non-assembler format, has been run the most often, ever, on this planet? By 'most often,' I mean the highest number of executions, regardless of CPU type. For the code in question, let's set a lower limit of 3 consecutive lines. For example, is it:
- A UNIX kernel context switch?
- A SHA2 algorithm for Bitcoin mining on an ASIC?
- A scientific calculation running on a supercomputer?
- A 'for-loop' inside on an obscure microcontroller that runs on all GE appliance since the '60s?"
For / While in C (Score:5, Funny)
}
OR
while(1){
}
Starts all main control loops and all kernels.
Re: (Score:2)
Fails the 3-line minimum.
Re:For / While in C (Score:5, Funny)
for(;;)
{
}
while(1)
{
}
Re: (Score:2)
come on now, three line minimum. That should be:
i
=
i+1;
Though granted that's a rephrasing of ++i rather than i++
Re: (Score:2)
for(;;)
{
}
you get 3. I'm sure that has to be the most executed sequence.
Re:For / While in C (Score:5, Funny)
it keeps going and going and going...
Re:For / While in C (Score:5, Informative)
Since no line "maximum" was defined I have to vote for SVCHOST running Windows update on XP....
Just to be accurate... we are shooting the messenger if we blame the SVCHOST process here. It runs various services. The faulty code was in the Windows Update service (wuauserv).
You can see all the respective services with the command tasklist /svc .
Re: (Score:2)
return 0;
}
Re: (Score:2)
Re: (Score:2)
That actually breaks the C standard, but I suppose control systems aren't much worried about portability.
Re: (Score:2)
Re:For / While in C (Score:5, Informative)
That actually breaks the C standard, but I suppose control systems aren't much worried about portability.
The ANSI C standard defines two types of implementations: "hosted" and "freestanding". An embedded system would most likely be considered a freestanding implementation, in which case, the entry point function can be whatever the implementation defines it to be. It might not even be named "main" (but if it is, it could return void if that's what the implementation says). That said, C99 allows main() to return void, even in a hosted implementation: 5.1.2.2.1 [coding-guidelines.com] gives "some other implementation-defined manner." as one of the options for main's definition. It notes in 5.1.2.2.3 [coding-guidelines.com] that "If the return type is not compatible with int, the termination status returned to the host environment is unspecified."
Re: (Score:2, Troll)
Re: (Score:2)
TFA: "let's set a lower limit of 3 consecutive lines."
Re: For / While in C (Score:5, Insightful)
Perhaps a pixel shader in a modern video game on console or PC, executed per pixel at HD resolution, and for hours (average play time) on tens of millions of machines?
Could be approaching 10^20 executions.
Re: (Score:3, Interesting)
Lines of code I've written in HDL execute in hardware once every clock cycle, at, say 100 MHz on maybe 50,000 devices for at least a few years of active use each. That's like 3x10^20 executions alone, and I work for a specialty hardware company which has only sold ~50,000 devices I've designed over the past 13+ years. I'm quite certain other hardware developers have far, far more, and the original question doesn't necessarily seem to require code that executes in a processor versus inferring hardware.
(And
Re: (Score:2)
Which one does the Linux kernel use?
Not sure, but OpenBSD has this at the very end of its main() [bxr.su]:
while (1)
/* NOTREACHED */
tsleep(&proc0, PVM, "scheduler", 0);
I tried finding the FreeBSD equivalent, but their (Newbus?) code makes it entirely non-obvious where the loop is. Feel free to try your luck — only the comment to what the startup function is supposed to do matches, but the rest is quite unique, even a different function name — mi_startup() on FreeBSD [bxr.su].
Re: (Score:3, Interesting)
I don't anything about the code that runs in digital watches, but maybe the code that says:
Is it time to trigger the alarm yet?
Yes? Trigger the alarm
No, check the time again.
I just imagine with the sheer number of watches, cel phones, microwaves, DVRs, etc. out there this would be the most ubiquitous, and constantly running, bit of code.
Re: (Score:3)
Re: For / While in C (Score:5, Interesting)
I work with a ton of electrical/controls engineers. Yes it is still probably true, mostly because it is still even cheaper/easier to do this through ladder logic. I forget the context of what we were talking about one day, but one day while talking to one of our SENIOR (30+ years) controls engineers I was explaining some logic that if we had to implement it in C# would take probably 300 lines of code. His reply was simply, psh, I could do that in 3 rungs, don't bother.
Obligatory (Score:5, Insightful)
Every Ask Slashdot gets a comment pointing out that it's the dumbest Ask Slashdot ever, I know.
This time, it's really, really the case.
Re:Obligatory (Score:5, Insightful)
I disagree. This may be the superlative of something, but I don't think "dumb" is it.
I actually think it's an interesting thought experiment. It immediately forces the reader to think about how pieces of code are used in the real world, both within and beyond their intended application. But it is also likely impossible to settle to anyone's satisfaction. I would trust a proposed answer to this question even less than I would an answer to "What was the size of the internet at the time of the Morris worm", or "How many lines of C code are there in existence".
Just because something's hard to measure doesn't make it dumb, though.
Re: (Score:3)
I actually think it's an interesting thought experiment.
I agree. But there's no way to get from that to this (I disagree with your reasoning):
This really is the worst ask /. I've ever seen.
Someone posted an interesting thought experiment to slashdot. That's great. The answers are interesting and come from many facets of tech/programming that I am not involved in.
We'll never know the absolute truth even if such a thing exists but the answers are interesting and informative.
I wish they'd asked something int
Re:Obligatory (Score:4, Interesting)
I know this is OT, but
Every Ask Slashdot gets a comment pointing out that it's the dumbest Ask Slashdot ever, I know.
This time, it's really, really the case.
True. But more importantly: I never knew /. let us do nested bold levels!
For anyone too lazy to look at the html source...
Re:Obligatory (Score:5, Insightful)
Re: (Score:3)
What's even more hilarious, people like the GP who claim to hate a type of article then proceed to post in each and every one of them are in reality raising two counters in a database somewhere when they #1 click on the article and #2 post a comment.
This indicates to slashdot that the article was both interesting to read as well as interesting enough to have participation, and the interpreted result is the readers want MORE articles of that nature!
So when people say "complaining is the only way to get chang
Re: (Score:3)
Every Ask Slashdot gets a comment pointing out that it's the dumbest Ask Slashdot ever, I know.
This time, it's really, really the case.
On the contrary. Unless you have a definitive and provably correct answer to this particular Ask Slashdot, which I didn't notice you providing, I would assert that it's an interesting question and you're just being a jackass.
Re: (Score:3)
Heh:
Ask Slashdot: What would be the best question to Ask Slashdot? :)
Bios code? (Score:3)
Re: (Score:3)
No. BIOS code only gets run at boot time.
Re:Bios code? (Score:5, Interesting)
I would probably have to say whatever is the inner loop on the system idle process in windows.
Re:Bios code? (Score:5, Informative)
I would probably have to say whatever is the inner loop on the system idle process in windows.
Ding, we have a winner. Not supercomputer code. Sure, supercomputers are... super and all, but the biggest one only has around 1 million processing cores. How many windoze machines are out there, idling away?
Re:Bios code? (Score:5, Insightful)
Actually, it's likely not executed that many times - the CPU goes into HALT when idle, and wakes up when there's work to do. Gone are the days of endlessly spinning....
The Idle Process may be more book-keeping artifact than actual code.
Re:Bios code? (Score:5, Informative)
That is also wrong.
HALT for the CPU means furtherhin it will do nothing.
Perhaps you ment a different opcode?
Halt means it does nothing... until the next interrupt. Which will happen when there's something useful to do.
Re: (Score:3)
Depends on the architecture. On many CPUs HALT stops it completely, never to resume until externally reset. There is usually a SLEEP op-code for what you are thinking of.
Re: (Score:2, Insightful)
Well, all of those Windows reboots ought to bump the value up a fair bit.
Re:Bios code? (Score:5, Insightful)
Lets approach this analytically.
What platform has the most computation power (number of CPUs x speed)?
Due to the increase in speed, we can disregard any CPUs built before 2000.
In number, mobile phones are the largest platform. So I would reckon, some GSM codec/cipher.
I think, for now, microcontrollers can be ignored, because they have much lower computational power.
Desktops and supercomputers have more power, but are they excessing the mobile phones? If they are a relevant portion, then across mobile phones and desktops, perhaps some code related to network access is the most-run.
I doubt it would be something kernel-related (like bootup, context-switching), because the kernel usually does not (or should not) take up a lot of the computing time. If we go by number of entries only, then perhaps some networking code.
If so, I'm not sure which layer to look into though. The lower ones are called more often, but media is not the same across use cases.
Re: (Score:3)
Come on.... ( pun intended )
It almost has to be a video / image codec if we are talking about internet era code. I mean the internet is what, 90% porn?
But in all seriousness, I would still say video codec code. All the devices out there consuming video at (usually) 24+FPS have to decode each frame. The line kind of blurs with DXVA / VDPAU and hardware decoding though.
Come to think of it, it could also easily be an audio codec, either in portable music players or cell phones.
Re: (Score:3)
So I would reckon, some GSM codec/cipher.
That is usually done by an ASIC though, so not code per-se. Parts of the radio in mobile phones are programmable, although they tend to be FPGAs rather than CPUs at the core because that reduces power when doing DSP type stuff. I'm not sure if FPGA code counts because it's not really executed like CPU code is.
There are a lot of similar candidates that fall into this trap. Hashing code, encryption code, checksumming code... Whenever it needs to be high performance it's usually better to create a hardware imp
Re:Bios code? (Score:5, Interesting)
(nearly) Every computer has a video device which has a loop running over the frame buffer, outputting pixels to the display output port. Even in the days of regular CGA 320x200 graphics on 60hz monitors that amounted to 3,840,000 iterations per second. We are talking over 3 decades of this going on, on nearly every desktop and laptop computer build during that time (vector displays worked differently) and even in those early days of CGA most of the time those machines were in a text mode with a pixel resolution of 720x240 and still putting out a 60hz of video signal (10,368,000 pixels per second.)
A single CGA desktop machine in text mode left on since January 1984 would have output 9,816,000,000,000,000 pixels to its display port so far. Thats nearly 10 quadrillion pixels. Even if the average number of running desktop computers over the period were only 1 million (a severe lowball) and used that shitty low resolution at only 60 hz, thats still over a sextillion iterations of that simple pixel outputting loop.
I would say the average number of running desktops over the period since 1984 is more like 50 million and the average resolution over the period was 1024x768, and the average monitor refresh is 70 hz. My guestimate is about 2.606E+24 iterations of the framebuffer loop, over 2 septillion iterations.
Re: (Score:3)
(nearly) Every computer has a video device which has a loop running over the frame buffer, outputting pixels to the display output port.
Unless you're using a Sinclair ZX80/81 or some other peculiar device that's too cheap to include a graphics chip, that's hardware, not 'code'. If you expand the definition of 'code' to VHDL and other hardware design languages, there must be 'code' doing far more than a graphics chip would.
Re: (Score:3)
Emphasis mine. There generally was only one *C*PU, but there may have been other ALU's or peripherals controllers (which includes graphics chips). Processors, yes, but not CPU's in the context of those systems. My mobile phone has at least 5 fully-functional ARM processors on it (not cores, processors), for example, but only one of those is the CPU.
Re:Bios code? (Score:4, Funny)
Hello World. (Score:5, Funny)
Indeed.
Slascode "asciifier" (Score:5, Funny)
Must be the SlashCode "asciifier" which removes all non-ASCII characters in summaries and posts, thus mangling a lot of names, locations and math formulas.
The code triggered by crtl-alt-del (Score:2)
By a long shot
Solved. Next? (Score:5, Insightful)
Question: What piece of code, in a non-assembler format, has been run the most often, ever, on this planet? By 'most often,' I mean the highest number of executions, regardless of CPU type.
Answer: Genetic code.
Re: (Score:2)
Insightful? Come off it. It's a pun.
Re: (Score:3)
It’s not really executable as I understand it, but I am not a biologist. The translation from DNA to RNA is hard to construe as ‘execution’. Then in the next step the RNA goes to ribosomes to construct proteins. So maybe DNA is ‘compiled’?
The field of computational biology would probably have a good metaphor to map the ideas from biology to computer science.
Re: (Score:3, Interesting)
It's not compiled, it's interpreted. If you had a single gigantic mRNA consisting of all your genes, that would be compilation.
You can think of DNA as source (in an extremely low-level language), mRNA as machine code, and ribosomes as microcontrollers. DNA transcriptase interprets DNA into RNA. In eukaryotes, SNRPs are optimizers (written by a lunatic, but no analogy is perfect) that rearrange the RNA; ribosomes interpret the RNA.
You've got lots of ribosomes in each cell, so think of each cell as a massi
Something in deep in a loop in the graphics system (Score:3)
of the Windows NT kernel that hasn't changed since the 1990s?
Re: (Score:2)
...of the Windows NT kernel that hasn't changed since the 1990s?
Because we know there's nothing like that in the Linux kernel...
Re: (Score:2)
Superintendent Chalmers: A graphics system... in the linux kernel... and hasn't changed... since the '90s?
Principal Skinner: Yes!
Superintendent Chalmers: May I see it?
Principal Skinner: Er, no.
How could this ever be determined or verified? (Score:4, Insightful)
How could this ever be more than a guess? How could it ever be determined, documented, or verified?
And for that matter, what is the definition of whether something is "the same" piece of code? For example, if the same source code compiles to different instructions on two platforms, are they running the same code?
How about if one of them actually compiles code that gets executed, and the other optimizes it out?
Re:How could this ever be determined or verified? (Score:5, Insightful)
How could this ever be more than a guess? How could it ever be determined, documented, or verified?
How many piano tuners are there in Chicago? [wikipedia.org]
this is easy.... (Score:2)
IEFBR14 - Mainframe Null Program (Score:5, Interesting)
http://en.wikipedia.org/wiki/IEFBR14
Any time a mainframe does anything with a dataset in a batch job (i.e. allocate, delete, whatever) it runs IEFBR14, a null program, as a target program to satisfy a requirement in how jobs are created.
This means that banks, retailers, governments, you name it--when they process the back-end records that make modern life functional, IEFBR14 usually gets invoked somewhere.
Re:IEFBR14 - Mainframe Null Program (Score:5, Interesting)
This gets my vote. Ran it many times myself.
As an aside, this program, (which did absolutely nothing and, in binary format, was originally only 2 bytes long) had the dubious reputation of being the shortest program with a bug. It failed to clear the register that returned the error code. Oops.
Re:IEFBR14 - Mainframe Null Program (Score:4, Insightful)
that is actually... really fucking sad. So sad it made me laugh. Is that in itself sad?
Re: IEFBR14 - Mainframe Null Program (Score:4, Informative)
Error? More like bad coding - it relied on the processor clearing the return/exit status register originally, and once the 'error' was 'corrected' it doubled the size of the program (from one BR14 instruction to a load instruction and then the branch instruction).
That code is now 50 years old.
Re: (Score:3)
The old classic... (Score:2)
Re: (Score:2)
Considering the number of Windows installations (Score:2)
My guess would be the code in 'System Idle Process'.
Initialize array to 0 (Score:4, Interesting)
for(int i=0; iSOME_LENGTH; i++){
array[i] = 0;
}
Run 100s of times per program, for almost all programs
Probably some telphone code (Score:4, Insightful)
eg. Call timer code in the 5ESS switch. Countless millions of times a day for over 30 years now. Probably the oldest code that we all depend on every day.
Re: (Score:3)
Re: (Score:2)
I'm having the same problem. I'm looking for a cell-phone with rotary dial.
Re: (Score:3)
Here you go:
https://www.sparkfun.com/products/retired/287 [sparkfun.com]
http://content.luxology.com/gallery/565fc4f98dd0a8d41c8f7ab8bf52457d.jpg [luxology.com]
Re: Probably some telphone code (Score:3)
Don't look to the US for sympathy - we paid a tax on our phone service for over a century to pay off the Spanish American War... 108 years to be precise !
http://usatoday30.usatoday.com/money/industries/telecom/2006-05-25-phone-tax_x.htm [usatoday.com]
ob (Score:5, Funny)
on anything {
displayHWinPtrAddrPtrScreen( {492EC5F8-477F-438E}.color.const::BLUE status:{492EC5F8-477F-438E}.const.DEATH } )
}
Highest number of executions (Score:2, Interesting)
The keyboard scan loop in Windows gets my vote.
Almost certainly microcode. (Score:2)
As most of us know, and the rest of us ought to, x86 and many other CISC architectures have their instruction set decoupled from the internal microarchitecture by using microcode [wikipedia.org].
Since multiple microcode instructions can run for one machine instruction, there's likely a sequence of three or more instructions used by many common instructions (I'm guessing something pertaining to checking for cache misses?) that thus gets executed more often than any single opcode on that machine.
Re: (Score:2)
Gah! I missed the "in a non-assembler format" qualifier. I'm not sure what exactly that means, but I suppose it was intended to rule out smart-ass answers like mine.
easy (Score:2)
i=i+1 or i+=1 or i++
Re: (Score:2)
For the code in question, let's set a lower limit of 3 consecutive lines.
You have failed to adhere to the asker's arbitrary criteria! Goodnight!
Given that the C64 is the best selling PC ever... (Score:2)
...and all you ever saw on store displays in the 80's was the result of:
10 PRINT "FUCK "
20 GOTO 10
I'd have to say that code is a contender.
Login.c (Score:2)
I'm fairly certain that all the BSD's including OS X use a standardized login.c Though my money would be on there being some system related windows code that has been the same since the 90s.
My guess (Score:2)
It's obvious... (Score:2)
int main (argc, argv)
char **argv;
{
Re: (Score:2)
At the risk of a "whoosh," none of that actually runs, though, does it?
Multiple choice? (Score:2)
idle time (Score:2)
Most OSes have some code that runs when other processes aren't running to measure the idle time. Certainly in Windows, this is a process in it's own right.
If the CPU is only 1% utilised, then the idle time process is consuming most of the remaining 99% (with the kernel using a bit of that).
So, I would hazard a guess that it's something in this.
(Or, for Windows, the code that swaps pages out to disk.)
Re: (Score:2)
On modern operating systems the idle loop is never coded in a high level language. It is painstakingly optimized in assembly language, for maximum speed.
code between semicolons? (Score:2)
i++
or
MOV EAX, [EBX]
or
INC EAX
XP kernel32.dll (Score:2)
Man file has run and still continues to run on more computers than ever before and frankly refuses to die. It won't ever go away.
Cell Phone code? (Score:2)
For an all-time high, you want a combination of a large number of devices, over a long period of time.
I'd say cell phones would do nicely. Probably something that runs often on all cells everywhere. Maybe something that sync's with cell towers, or handles jumping between towers.
Maybe text message handling code. How many texts are sent per day?
Re: (Score:2)
I reckon... (Score:2)
Ignoring the '3 line' thing because that's just dumb, my vote for the most run piece of code on the planet right now would be:
DNS. Either the part that queries or the part that answers.
Think about how many times that's being called at this moment, globally.
(And yes, this Ask /. is the stupidest ever.)
Pi (Score:2)
The routine used in calculating Pi.
int a=10000,b,c=2800,d,e,f[2801],g;main(){for(;b-c;)f[b++]=a/5;
for(;d=0,g=c*2;c-=14,printf("%.4d",e+d/a),e=d%a)for(b=c;d+=f[b]*a,
f[b]=d%--g,d/=g--,--b;d*=b);}
Microcontrollers... (Score:2)
Borg's backdoor (Score:2)
fractal geometry (Score:2)
For a GIF of less than two million pixels, say 1600x1200, and each pixel's colour selected from a palette of 256 colours and dependent on neighbouring pixels' colour values derived from the same iterative algorithm run 1 million times to maximise value stability per pixel, you're looking at running the same line of code 4.9152*10^14 times.
Assuming 100% (as in perfect) saturation on a 2GHz processor core, that'll take just over 68 hours.Or, to use the old industry yardstick, 63.2 P90-days.
(source: mad guy wi
Just my guess. (Score:2)
Based on the number of graphics cards out there, the high repetitive nature of their application and the fact that that's all they do, it's probably something related to them. I thought of supercomputers running very small recursive routines, but they usually have a limited lifetime and older computers aren't fast enough and haven't continued to run in any event.
Graphics though? I'd guess something in a very common graphics card would probably be in the scale to achieve the title of most-run code.
Though if
Scrypt (Score:3, Interesting)
{
uint8_t * z = (uint8_t *)blah;
z[0] = (a >> 24) & 0xff;
z[1] = (a >> 16) & 0xff;
z[2] = (a >> 8) & 0xff;
z[3] = a & 0xff;
}
Clock counting loops (Score:3)
The counters in digital clocks have furiously been counting clock ticks to the next second since the '70s, if not earlier.
Re: (Score:2)
Probably some loop used in Bitcoin mining.
Most bitcoins are mined with ASICs or FPGAs, so that doesn't count as "code" since the algorithm runs directly in hardware. If you believe that algorithms implemented in Verilog or VHDL should count, then the "winner" still wouldn't be bitcoin, but something like the VHDL that implements the system clock on a billion x86s.
Re:Bitcoin (Score:5, Informative)
Re: (Score:2)
> I think the OP meant 'machine code.'
machine code OTOH is what gets executed.
It's all math (Score:2)
Aren't all string instructions essentially math instructions? In fact, aren't all software instructions of any type reducible to mathematics when you get down to the metal?