tic - Start stopwatch timer - MATLAB (original) (raw)

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Syntax

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.

example

timerVal = tic stores the current time intimerVal so that you can pass it explicitly to thetoc 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 thetoc function.

example

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 0.805683 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 0.769707 seconds.

Elapsed time is 0.860179 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)

tEnd = toc(tStart) % pair 2: toc

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 andtoc 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 timetimeit
  • Using tic and toc within a function timed by timeit

Extended Capabilities

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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 MATLABtic 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 functionsQueryPerformanceFrequency andQueryPerformanceCounter.
  • In all other cases, the implementation uses the POSIX APIclock_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.

Version History

Introduced before R2006a