timeit - Measure time required to run function - MATLAB (original) (raw)

Measure time required to run function

Syntax

Description

t = timeit([f](#btx36ta-f)) measures the time (in seconds) required to run the function specified by the function handle f. In order to perform a robust measurement, timeit calls the specified function multiple times and returns the median of the measurements. If the function runs fast, timeit might call the function many times.

example

t = timeit([f](#btx36ta-f),[numOutputs](#btx36ta-numOutputs)) calls f with the desired number of outputs, numOutputs. By default, timeit calls the function f with one output (or no outputs, if the function does not return any outputs).

example

Examples

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Use timeit to time a function call to date. This example uses a handle to a function that accepts no input.

Time the combination of several mathematical matrix operations: matrix transposition, element-by-element multiplication, and summation of columns.

A = rand(12000,400); B = rand(400,12000); f = @() sum(A.'.*B, 1); timeit(f)

Determine how long it takes to run svd with one output argument, s = svd(X).

X = rand(100); f = @() svd(X); t1 = timeit(f)

Compare the results to svd with three output arguments, [U,S,V] = svd(X).

Create a short function to allocate a matrix using nested loops. Preallocating an array using a nested loop is inefficient, but is shown here for illustrative purposes.

function mArr = preAllocFcn(x,y) for m = 1:x for n = 1:y mArr(m,n) = 0; end end end

Compare the time to allocate zeros to a matrix using nested loops and using the zeros function.

x = 1000; y = 500; g = @() preAllocFcn(x,y); h = @() zeros(x,y); diffRunTime = timeit(g)-timeit(h)

Input Arguments

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Function to be measured, specified as a function handle. f is either a handle to a function that takes no input, or a handle to an anonymous function with an empty argument list.

Number of desired outputs from f, specified as an integer. If the function specified by f has a variable number of outputs, numOutputs specifies which syntax timeit uses to call the function. For example, the svd function returns a single output, s, or three outputs, [U,S,V]. Set numOutputs to 1 to time the s = svd(X) syntax, or set it to 3 to time the [U,S,V] = svd(X) syntax.

Tips

• The following actions result in unexpected output:
  • Using timeit between tic and toc
  • Using timeit to time a function that includes calls to tic and toc
  • Using timeit recursively

Extended Capabilities

Version History

Introduced in R2013b