parallel.pool.ActivityMonitor

Parallel pool activity monitor

Since R2025a

Description

Use ActivityMonitor to monitor and collect data on worker activity in a parallel pool.

Monitoring data includes:

• The type of parallel construct, such as parfor, parfeval, and spmd.

• The amount of data (in bytes) the client and workers send and receive.

• The time each worker spends processing their portion of the parallel code.

You can retrieve the monitoring results using the results function and view the monitoring data in the Pool Dashboard.

Creation

Syntax

monitor = parallel.pool.ActivityMonitor

monitor = parallel.pool.ActivityMonitor(pool)

monitor = parallel.pool.ActivityMonitor(___,Start=false)

Description

monitor = parallel.pool.ActivityMonitor creates an ActivityMonitor object and starts collecting activity monitoring data on the current parallel pool. If no parallel pool exists, parallel.pool.ActivityMonitor starts a new parallel pool using the default profile, unless you disable automatic pool creation in your parallel settings.

To save monitoring results, use the results function. To stop collecting and save monitoring results, use the stop function.

monitor = parallel.pool.ActivityMonitor(pool) starts collecting activity monitoring data on the parallel pool specified by pool.

monitor = parallel.pool.ActivityMonitor(___,Start=false) creates an ActivityMonitor object but does not start collecting activity monitoring data. To start collecting monitoring data, use the start function.

Input Arguments

pool — Parallel pool

parallel.Pool.ProcessPool object | parallel.pool.ClusterPool object

Parallel pool, specified as a parallel.Pool.ProcessPool or parallel.pool.ClusterPool object.

You can use an interactive or batch parallel pool. ActivityMonitor is not supported on parallel pools of thread workers.

Example: parpool("Processes");

Example: batch(...,Pool=4);

Output Arguments

monitor — Pool activity monitor

ActivityMonitor object

Pool activity monitor, returned as an ActivityMonitor object.

Object Functions

results	Retrieve results from parallel pool activity monitor
stop	Stop monitoring parallel pool activity
start	Start collecting parallel pool activity monitoring data

Examples

Monitor Activity on Interactive Pool

Create an ActivityMonitor object to start collecting pool monitoring data. With default settings, parallel.pool.ActivityMonitor automatically starts an interactive parallel pool using the default profile if one does not exist.

monitor = parallel.pool.ActivityMonitor;

Starting parallel pool (parpool) using the 'Processes' profile ...
Connected to parallel pool with 6 workers.

Run a parfor-loop to generate random numbers and store them in an array.

data = zeros(1,100);
parfor idx = 1:100
    data(idx) = rand;
end

Stop the activity monitor and retrieve the results collected during the parfor execution.

monitorResults = stop(monitor);

Create Activity Monitor for Specific Pool

Create a parallel pool using the cluster profile, MyCluster.

pool = parpool("MyCluster");

Create an ActivityMonitor object to collect monitoring data for the pool but do not start collecting data immediately.

monitor = parallel.pool.ActivityMonitor(pool,Start=false);

Monitor Activity on Batch Pool

Collect activity monitoring data on a batch pool job using an ActivityMonitor object.

Write a function that creates an ActivityMonitor object to collect monitoring data, executes parallel tasks, and collects pool monitoring results.

function monitorResults = myParallelCode

monitor = parallel.pool.ActivityMonitor;

f(1:100) = parallel.FevalFuture;
for idx = 1:100
    f(idx) = parfeval(@(n) real(eig(randn(n))),1,5e2); 
end
maxFuture = afterEach(f,@max,1);
wait(maxFuture);

monitorResults = stop(monitor);
end

Run the myParallelCode function as a batch pool job using the myCluster profile and wait for the batch job to complete.

j = batch(@myParallelCode,1,Pool=4,Profile="myCluster");
wait(j);

Fetch the monitoring results from the completed batch job.

out = fetchOutputs(j);
monitoringResults = out{1};

Limitations

• ActivityMonitor is not supported on parallel pools of thread workers.

Alternative Functionality

Tool

You can use the Pool Dashboard to collect and view pool monitoring data on an interactive parallel pool.

Version History

Introduced in R2025a