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tic

Start stopwatch timer

Syntax

tic
timerVal = tic

Description

tic starts a stopwatch timer to measure performance. The function records the internal time at execution of the tic command. Display the elapsed time with the toc function.

timerVal = tic returns the value of the internal timer at the execution of the tic command, so that you can record time for simultaneous time spans.

Output Arguments

timerVal

Value of the internal timer at the execution of the tic command. This value is used as an input argument for a subsequent call to toc. You should not rely on the meaning of this value.

Examples

Measure time to generate two random matrices and compute element-by-element multiplication of their transposes.

tic
A = rand(12000, 4400);
B = rand(12000, 4400);
toc
C = A'.*B';
toc
 

Measure how the time required to solve a linear system varies with the order of a matrix:

t = zeros(1,100);
for n = 1:100
    A = rand(n,n);
    b = rand(n,1);
    tic;
    x = A\b;
    t(n) = toc;
end
plot(t)
 

Measure multiple time spans simultaneously using two pairs of tic/toc calls. To do this, measure the minimum and average time to compute a summation of Bessel functions:

REPS = 1000;   minTime = Inf;   nsum = 10;
tic;  % TIC, pair 1

for i=1:REPS
   tStart = tic;  % TIC, pair 2  
   total = 0;
   for j=1:nsum 
      total = total + besselj(j,REPS);
   end

   tElapsed = toc(tStart);  % TOC, pair 2  
   minTime = min(tElapsed, minTime);
end
averageTime = toc/REPS;  % TOC, pair 1  

More About

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Tips

  • Consecutive tic commands overwrite the internally recorded starting time.

  • The clear function does not reset the starting time recorded by a tic command.

  • The following actions result in unexpected output:

    • Using tic and toc to time timeit

    • Using tic and toc within a function timed by timeit

See Also

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