how to massure cpu time to evalute sorting algorithems

[bary2000]

hi
I am writing a program that have some sorting algorithms, and i want to compare between this algorithms and i need the code in C++ to see how much the cpu take time to execute each algorithm.

[weaknessforcats]

Easier said than done. It depends on a) the CPU, b) what else is running on the machine, c) buffering, d) randomness of the data, e) the operating system, f) number of cores, etc...

You might do some research on profiling. You may find that your measurement comes form controlled executions rather than direct CPU usage measurements.

[logicbloke]

The time ? if that's what you're looking for, include time.h then declare two
variables, with clock_t as type, just like the following

[CODE=C]clock_t start,end;

start = clock(); //mark the beginnning
function();
end = clock(); // mark the end
printf("Time elapsed : %ld ms.",(end-start)*1000/CLOCKS_PER_SEC) ;
[/CODE]
CLOCKS_PER_SEC is a constant that will let you know how many clocks your configuration (hardware+softw are) generates per second.

I hope this helps

[Banfa]

Unfortunately on todays multicore processors and multitasking operating systems that doesn't work.

clock() returns the number of clock ticks elapsed since the program was launched. On such an operating sytem your algorithm ends up measuring not just how long the algorithm took to run but also any operating system activity and the runtime of any other programs that received processor time while your program was running.

If you want to know how long a particular algorithm (or function) is taking to run in a program probably your best bet is to get a decent profiler.

Some operating systems (including Windows) can provide information on how much processor time a specific process (or thread) has had in which case writing a small test program for the algorithm/function and then accessing the OS stats might be of use.