How to get number of processor cycles since start up

Hi,
I'm looking to make a random number generator and want to multiply the number generated by the C random number generator by the number of processor cycles there has been since start up. Is there a way to get the number of processor cycles there has been in C?


Thanks in advance.

I don't think there's such a function. It would be incredibly unreasonable.
Are you sure you don't mean the time since start up?

Not for the CPU, although you can get such information from your graphics card, although it will be in GPU clock cycles, which are usualyl much slower than the CPU.

Since the startup of what
- your program
- your machine
?

I can imagine the time since program start might be fairly constant, which isn't going to help you much.

You should also know that
srand( time(NULL) );
isn't going to be any less random than
srand( exoticTimeFunction() );

Don't know what you want to do, but your idea doesn't sound really great. The standard rand() function will do the job in (i would say) at least 99% of the case. If what you are looking for is creating a random number generator who can generates numbers on a larger interval than 0 - RAND_MAX, then there might be better way to do so than multiplying the result of rand() by the number of clock cycle since the start of the program/machine. I guess it could work, but this could also be unreliable.

Also, if you want to know, you can get the number of clock cycles since the processor is turned on by using the RDTSC instruction (if you are running on a IA-32 or Intel 64 architecture processor). If you want more information about using this instruction, you can refer to this link (warning for slow connection: 9 MB PDF).