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# tic

Start stopwatch timer

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

expand all

### 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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