How long time does CPU need to execute a single command?

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Can you tell me how to calculate the time which CPU had used?

Example:
----------------------

C#

public int Main()
{

int a, b, c;
a = 1; b = 2;
return (c = a + b);

}

----------------------

If we ignore these time: compiling, provide varibles storage, load data to stack/heap...
Then, how to know the nanoseconds to execute this command by CPU Registers:

C#

return (c = a + b);

Thanks for solutions!

Posted 4-Sep-14 22:28pm

user8x86

Updated 4-Sep-14 22:48pm

v2

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Mehdi Gholam 5-Sep-14 4:29am

Why?

user8x86 5-Sep-14 4:31am

i don't understand your mean.

Mehdi Gholam 5-Sep-14 4:46am

Timing a single command makes no sense and has no value by it's self, using timings only makes sense if you have a performance problem.

Dilan Shaminda 5-Sep-14 4:42am

use Stopwatch Class in .Net to measure execution time

user8x86 5-Sep-14 7:20am

Thank Dilan. But Stopwatch Class does not give to me the exactly time. I might to wait for loading Stopwatch start, after that, keep waiting for Stopwatch stop.

Dilan Shaminda 5-Sep-14 10:38am

not giving exact time means? get an average time. run your code like 10,000 times and calculate the CPU time and then get the avarage

user8x86 5-Sep-14 11:08am

That worked. But I mean that I will try it 1 times, following this step: sw.Start() ==>> run the command ==>> sw.Stop() ==>> show the time.

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Duncan Edwards Jones · Answer 1 · 2014-09-04T22:37:00

Solution 1

The addition is one machine instruction, and copying into a buffer is another so 2 clock cycles is the absolute minimum. So - .00000005 seconds (+/- 100%)

Posted 4-Sep-14 22:37pm

Duncan Edwards Jones

kavitha3 · Answer 2 · 2014-09-04T22:40:00

Solution 2

Hi ,
I am not understanding what is your need and why ...
But i can redirect u to Mr.Robert's Article.

Its about ::How To: Measure execution time in C#[^]::

Posted 4-Sep-14 22:40pm

kavitha3

Comments

user8x86 5-Sep-14 4:45am

I mean: I wanna know about how long time does CPU Registers take to run the command: return (c = a + b);

Rob Philpott · Answer 3 · 2014-09-04T23:06:00

Solution 3

You can't. Depends on what speed the CPU is clocked at, what instruction set its running, what the JIT does, whether it gets 'inlined' or branched etc.

Posted 4-Sep-14 23:06pm

Rob Philpott

user8x86 · Answer 4 · 2014-09-04T23:16:00

Solution 4

Your mean is: The time - which Microsoft calculates in order to "swap out" any process and "swap in" another process - is static (Can't be changed)?

Posted 4-Sep-14 23:16pm

user8x86