Tic toc without output
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Barbaros Teoman Kosoglu
el 13 de Oct. de 2022
Respondida: John D'Errico
el 13 de Oct. de 2022
I want to use tic toc to calculate time. But when the matrix is getting bigger the command window becomes unreadable. So is there a way to use tic toc without outputting the function.
calcDimTime(50)
calcDimTime(100)
calcDimTime(200)
calcDimTime(400)
function calcDimTime(n)
A = hilb(n);
tic
inv(A)
t = toc;
sprintf("The dimension of a is %f %f, and " + ...
"the time to calculate the inverse of A " + ...
"is %f",size(A),t)
end
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John D'Errico
el 13 de Oct. de 2022
First, using tic and toc are bad ways to compute the time to do something. Why? They compute only ellapsed time, and even then, only poorly so. They compute the time for only one run of the code. Better to average things. Better to discard the first couple of times you call a code. Why? There is a warm-up needed, to get the true time. The first time you call a code, you also see the time needed to cache it, etc.
And of course, you need to make sure you are doing nothing else at the same time. Don't go surf the we, etc. That sucks time away from your CPU. Even in my case, I'm running MATLAB flat out right now to do a computation, one that is uusing one core of my CPU full time. So while I have an 8 core CPU, I can see if I start doing something one the side, as I am monitoring the time needed while it truns.
Anyway, MATLAB provides the timeit utility. USE IT!
If your problem is dumping crap in the command window, use semi-colons! All of this is avoided using timeit. So, we can do this:
N = 1000000;
tic,
p = primes(N);
toc
tic,
p = primes(N);
toc
tic,
p = primes(N);
toc
Or, this:
timeit(@() primes(N))
The latter is going to be far more consistent. Do you see the significant variance in times reported from tic and toc?
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