tic

Start stopwatch timer

Description

example

tic works with the toc function to measure elapsed time. The tic function records the current time, and the toc function uses the recorded value to calculate the elapsed time.

example

timerVal = tic stores the current time in timerVal so that you can pass it explicitly to the toc function. Passing this value is useful when there are multiple calls to tic to time different parts of the same code. timerVal is an integer that has meaning only for the toc function.

Examples

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Measure the time required to create two random matrices.

tic
A = rand(12000,4400);
B = rand(12000,4400);
toc
Elapsed time is 1.478286 seconds.

Measure the elapsed time since a call to the tic function at different points of the program.

tic
A = rand(12000,4400);
B = rand(12000,4400);
toc
Elapsed time is 1.105916 seconds.
C = A.*B;
toc
Elapsed time is 1.286162 seconds.

Use a pair of tic and toc calls to report the total time required for element-by-element matrix multiplication; use another pair to report the total runtime of your program.

tStart = tic;           % pair 2: tic
n = 10;
T = zeros(1,n);
for i = 1:n
A = rand(12000,4400);
B = rand(12000,4400);
tic         % pair 1: tic
C = A.*B;
T(i)= toc;  % pair 1: toc
end
tMul = sum(T)
tMul = 0.5607
tEnd = toc(tStart)      % pair 2: toc
tEnd = 10.9665

The variable tMul includes the total time spent on multiplication. tEnd specifies the elapsed time since the call to the tic function at the beginning of the program.

Tips

• Consecutive calls to the tic function overwrite the internally recorded starting time.

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

• Sometimes programs run too fast for tic and toc to provide useful data. If your code is faster than 1/10 second, consider measuring it running in a loop, and then average to find the time for a single run. For more information, see Measure the Performance of Your Code.

• The following actions result in unexpected output:

• Using tic and toc to time timeit
• Using tic and toc within a function timed by timeit