Why matlab execution time differs when pressing F9

Question

I have a pretty simple situation where matlab execution time differs depending on the way I run the code :

tic
pause(1)
toc

If I press Ctrl+Enter on a script, I get something like :

Elapsed time is 1.000241 seconds.

If I select the code and press F9, I get something like :

Elapsed time is 1.025203 seconds

I notice a 25ms time difference which is reproducible.

Answer 1

if you copy and past your code in Matlab "Command Window" you see big difference as compare running your code as a m file.

on my computer (Intel i7, 16GB RAM), my result is varying +/- 5ms.

Elapsed time is 1.002843 seconds.
Elapsed time is 1.008236 seconds.
Elapsed time is 1.003001 seconds.

but as I run the code in a m file, I get much accurate result. +/- 0.01ms

Elapsed time is 1.000032 seconds.
Elapsed time is 1.000041 seconds.
Elapsed time is 1.000021 seconds.

and the possible reason is: If you run the code as m file, matlab try to pars the code in advance and your code will be run quicker and there is no intermediate parsing phase for each individual lines.