toc - Read elapsed time from

stopwatch - MATLAB (original) (raw)

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Read elapsed time from stopwatch

Syntax

Description

toc reads the elapsed time since the stopwatch timer started by the call to the tic function. MATLAB® reads the internal time at the execution of the toc function and displays the elapsed time since the most recent call to thetic function without an output. The elapsed time is expressed in seconds.

example

toc([timerVal](#bswh%5Fpb-1-timerVal)) displays the elapsed time since the call to the tic function corresponding totimerVal.

elapsedTime = toc returns the elapsed time since the most recent call to the tic function.

example

elapsedTime = toc([timerVal](#bswh%5Fpb-1-timerVal)) returns the elapsed time since the call to the tic function corresponding totimerVal.

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.

Input Arguments

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Value of the internal timer saved from a previous call to thetic function, specified as a scalar of typeuint64.

Tips

• Consecutive calls to the toc function with no input return the elapsed time since the most recent call to tic. This property enables you to take multiple measurements from a single point in time.
  Consecutive calls to the toc function with the sametimerVal input return the elapsed time since thetic function call that corresponds totimerVal.
• 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 toc is different between MATLAB and the generated code. To avoid errors, do not use a MEX-function toc output value in MATLAB, or a MATLABtoc 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 toc 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