parfor

Parallel for-loop

Syntax

parfor loopvar = initval:endval,, statements;
end

parfor (loopvar = initval:endval, M); statements;
end

Description

parfor loopvar = initval:endval,, statements; end executes a series of MATLAB^® statements for values of loopvar between initval and endval, inclusive, which specify a vector of increasing integer values. The loop runs in parallel when you have Parallel Computing Toolbox™ or when you create a MEX function or standalone code with MATLAB Coder™. Unlike a traditional for-loop, iterations are not executed in a guaranteed order. You cannot call scripts directly in a parfor-loop. However, you can call functions that call scripts.

example

parfor (loopvar = initval:endval, M); statements; end executes statements in a loop using a maximum of M workers or threads, where M is a nonnegative integer.

Examples

collapse all

Calculate Eigenvalues Using Three Workers

Perform three large eigenvalue computations using three workers or cores with Parallel Computing Toolbox:

parpool(3)
parfor i=1:3, 
    c(:,i) = eig(rand(1000)); 
end

Tips

If you have Parallel Computing Toolbox, see for parfor (Parallel Computing Toolbox) and parpool (Parallel Computing Toolbox) for additional information.
If you have MATLAB Coder, see parfor (MATLAB Coder) for additional information.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Treated as a for-loop in a MATLAB Function block or when used with fiaccel.
See parfor (MATLAB Coder) in MATLAB Coder.
See Generate Code with Parallel for-Loops (MATLAB Coder).

Automatic Parallel Support
Accelerate code by automatically running computation in parallel using Parallel Computing Toolbox™.

If you have Parallel Computing Toolbox installed, then when you use parfor, MATLAB automatically opens a parallel pool of workers on your local machine. MATLAB runs the loop across the available workers. Control parallel behavior with the parallel preferences, including scaling up to a cluster.

For details, see Parallel for-Loops (parfor) (Parallel Computing Toolbox).

Version History

Introduced in R2008a