tic

Start stopwatch timer

Syntax

tic

timerVal = tic

Description

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.

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

Measure Time to Create Random Matrices

Measure the time required to create two random matrices.

tic
A = rand(12000,4400);
B = rand(12000,4400);
toc

Elapsed time is 1.491844 seconds.

Measure Multiple Intervals from One tic Call

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 1.167408 seconds.

C = A.*B;
toc

Elapsed time is 1.366986 seconds.

Take Measurements Using Multiple tic Calls

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 = 0.4054

tEnd = toc(tStart)      % pair 2: toc

tEnd = 12.2519

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

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• The data type returned from tic is different between MATLAB^® and the generated code. To avoid errors, do not use a MEX-function tic output value in MATLAB, or a MATLAB tic output value in a MEX function.

• If you call tic in a MATLAB session and toc in a MEX function, or vice versa, the timing results are not coordinated.

• The C/C++ implementation for tic in the generated code differs depending on the hardware settings stored in the code generation configuration object. By default, the hardware settings are configured for the host platform, with Hardware Board in the MATLAB Coder™ app set to MATLAB Host Computer.

  • When generating code on Windows^® with Windows-compatible hardware settings, the generated C/C++ implementation uses the Windows API functions QueryPerformanceFrequency and QueryPerformanceCounter.

  • In all other cases, the implementation uses the POSIX API clock_gettime. When compiling code that uses the POSIX API, the preprocessor macro _POSIX_C_SOURCE must be set to an integer greater than or equal to 199309L. The code generator sets the macro to 199309L for compilation.