MATLAB: Does keyboard slows down the code

speed

Hello.
I was doing some tests to speed up my code, and I realized that having a keyboard in the code slows it down, even if the keyboard is actually never hit.
Here's a code to check it:
% speed test
a = rand;
tic
for i = 1:1e4
if a == 0
keyboard
end
end
toc
tic
for i = 1:1e4
if a == 0
b = 5^2;
end
end
toc
Elapsed time is 0.000195 seconds.
Elapsed time is 0.000025 seconds.
How can this be possible?

Best Answer

  • Its to do with the JIT optimisation, the same is true if you insert conditional debug statement in the code, Matlab needs to prepare to stop execution.