BackgroundPool - Environment for running code in the background - MATLAB (original) (raw)

Environment for running code in the background

Since R2021b

Description

Use the background pool to run code in the background. When you run code in the background, you can run other code in your MATLAB® session at the same time.

Creation

Syntax

Description

`p` = backgroundPool returns the background pool.

example

Properties

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FevalQueue — Queue of FevalFuture objects to run on the background pool

FevalQueue object

This property is read-only.

Queue of FevalFuture objects to run on the background pool, specified as an FevalQueue object. You can use this property to check the pending and running future variables of the parallel pool. To create future variables, use parfeval (Parallel Computing Toolbox) and parfevalOnAll (Parallel Computing Toolbox). For more information on future variables, see Future.

Data Types: FevalQueue

NumWorkers — Number of workers

positive integer scalar

This property is read-only.

Number of workers, specified as a positive integer scalar.

• If you do not have a license for Parallel Computing Toolbox™, the value is 1.
• If you have a license for Parallel Computing Toolbox, NumWorkers is equal to the number of physical cores you have. For example, if you run MATLAB on a machine with four physical cores, the value is 4. You can reduce this value usingmaxNumCompThreads before first usage of backgroundPool.

Busy — Flag that indicates whether the background pool is busy

true | false

This property is read-only.

Flag that indicates whether the background pool is busy, specified astrue or false. The pool is busy if there is outstanding work for the pool to complete.

Object Functions

Examples

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Run Functions in Background

This example shows how to run a function in the background using parfeval and backgroundPool. When you run a function in the background, you can run other MATLAB® code at the same time.

Use parfeval to run the function magic(3) and retrieve one output. Specify backgroundPool as the first argument to run the function in the background. When you use parfeval, you create a Future object.

f = parfeval(backgroundPool,@magic,1,3);

To retrieve the output from the background, use fetchOutputs. MATLAB returns the output once the execution of magic is complete.

ans = 3×3

 8     1     6
 3     5     7
 4     9     2

Read Images from S3 Bucket in Background

This example shows how to read images from an Amazon® S3 bucket in the background.

Use an image datastore to connect to your bucket. For more information on how to set up access to your S3 bucket, see Work with Remote Data.

Replace "s3://MyBucket/data" with a URL to a data folder in your S3 bucket.

ds = imageDatastore("s3://MyBucket/data");

Use parfeval to read data from the S3 bucket. Specify backgroundPool as the first argument to run the function in the background. Then, read all of the data from the datastore.

f = parfeval(backgroundPool,@readall,1,ds);

You can run other functions while you download the data from the S3 bucket. To retrieve all of the images from the background, use fetchOutputs. MATLAB returns the output once the execution of readall is complete.

T = fetchOutputs(f); imout = imtile(T); imshow(imout)

Limitations

• Pools created using parpool(‘Threads’) and backgroundPool are both thread-based pools which utilize the same resources. It is possible that activity on one pool may block activity on the other and vice versa. Additionally, persistent data and random number generation stream state are shared in between these pools. For more information on controlling random number streams, see Control Random Number Streams on Workers (Parallel Computing Toolbox).

Extended Capabilities

Thread-Based Environment

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

Usage notes and limitations:

• Calling backgroundPool on thread-workers returns an emptybackgroundPool object. Any code you run in the background of a thread-worker is evaluated serially.

For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced in R2021b