toc

Read elapsed time from stopwatch

Syntax

toc

toc(timerVal)

elapsedTime = toc

elapsedTime = toc(timerVal)

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 the tic function without an output. The elapsed time is expressed in seconds.

toc(timerVal) displays the elapsed time since the call to the tic function corresponding to timerVal.

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

elapsedTime = toc(timerVal) returns the elapsed time since the call to the tic function corresponding to timerVal.

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.

Input Arguments

timerVal — Value of internal timer

8-byte (64-bit) unsigned integer

Value of the internal timer saved from a previous call to the tic function, specified as a scalar of type uint64.

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 same timerVal input return the elapsed time since the tic function call that corresponds to timerVal.

• 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 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 MATLAB toc 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 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.