Why is tic/toc not reporting the correct elapsed time?

I'm trying to time how long it takes for my program to run and tic/toc is reporting an elapsed time of 150 seconds, but when I time it with a stopwatch, it actually takes 3 hours and 24 minutes for my program to run.

Why is there such a significant discrepancy?

[madhan ravi]

mind attaching the file?

[Ewen Chan]

Unfortunately, I can't.

It's proprietary/confidential.

The basis of my question really lies in what does tic/toc actually time if the corresponding results in such a drastic difference in the timing results.

[Walter Roberson]

Are you saving the result of tic() into a variable and toc() against the variable? If not then you might have another tic() call that is interfering: toc() reports relative to the most recent tic() that had no output.

[Ewen Chan]

To be honest, I'm not really sure. I have just been reassigned, so the code is new to me.

What I'm doing is I've wrapped the execution command with tic/toc.

The code times itself and generates a summary automatically for the actual runtimes, but I'm still not sure about the finer workings of it as it is a very complicated multi-system code. There's a LOT to it.

Answer 1

[Bruno Luong]

I never have problem with tic/toc. I believe it inquires CPU frequency/counter or clock and derive time from it. It's very direct and simple.

If you get some strange result, then as Walter said something must trigger a later tic when you are not expected.

It might be also safter using tic/toc with timerVal

t0 = tic();
...
dt = toc(t0)

if you are not sure about what happens during "..."

[Ewen Chan]

I'll try this today and hopefully, it'll produce a result that's more in line with the internal timers that have been built into the code/program itself.

Thank you.