spmdSize

Number of workers running current spmd block

Since R2022b

Syntax

n = spmdSize

Description

n = spmdSize returns the number of workers running the current spmd block or communicating job. This value is the maximum value that you can use as the destination input to spmdSend and source input to spmdReceive.

Examples

Find Number of Workers in spmd Block

This example shows how to run spmdSize inside and outside an spmd block.

Create a parallel pool with four workers.

parpool(4);

When you execute an spmd block after creating a parallel pool, by default all available workers in the pool run the code inside the spmd block.

Run spmdSize inside and outside an spmd block. In the block, the returned value is equal to the number of workers. Outside the block, the returned value is 1.

spmd
    disp(spmdSize)
end
disp(spmdSize)

Worker 1: 
       4
  
Worker 2: 
       4
  
Worker 3: 
       4
  
Worker 4: 
       4
  
     1

Output Arguments

n — Number of workers

positive integer

Number of workers running the current spmd block or communicating job, returned as a positive integer. In an spmd block, n is the number of workers running the spmd block. Outside an spmd block, n is 1.

When you create a communicating job using createCommunicatingJob, you can run a function or script on n workers. When one of the workers runs spmdSize, the returned value is n.

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced in R2022b