Flutter 3 Isolate vs. Compute: A Deep Dive into Concurrency in Flutter

In the world of app development, performance is key. Users expect smooth and responsive applications that can handle complex tasks efficiently. To achieve this, developers often turn to techniques such as parallel processing to optimize their apps. In Flutter, a popular UI toolkit for building cross-platform applications, two commonly used approaches for parallel processing are Isolate and Compute. In this article, we’ll explore the differences between Flutter Isolate and Compute and when to use each one.

Flutter Isolate:

Flutter Isolate is a feature that allows developers to run Dart code in a separate isolate, a lightweight thread of execution. This separate isolate runs in its own memory space, independent of the main isolate where the UI runs. Flutter Isolate can perform computations parallel to the UI without blocking the main thread and affecting the app’s responsiveness.
Flutter Isolate is ideal for performing CPU-intensive tasks such as complex calculations, image processing, or data parsing. By offloading these tasks to separate isolates, developers can ensure that the main UI thread remains responsive, providing a smooth user experience. Flutter Isolate also supports bidirectional communication with the main isolate, allowing data to be passed back and forth between isolates.
One key feature of Flutter Isolate is its ability to handle multiple isolates. This means developers can create and manage multiple isolates concurrently, each performing a different task or computation. This makes Flutter isolate highly scalable and suitable for applications that require parallel processing of multiple tasks simultaneously.

import 'dart:isolate';

void main() async {
  // Spawn a new isolate
  Isolate isolate = await Isolate.spawn(runIsolate, 'Hello from isolate!');

  // Send a message to the isolate
  isolate.sendPort.send('Message from main isolate!');

  // Receive a message from the isolate
  ReceivePort receivePort = ReceivePort();
  isolate.addOnExitListener(receivePort.sendPort);
  receivePort.listen((dynamic message) {
    print('Received message in main isolate: $message');
  });
}

void runIsolate(dynamic message) {
  print('Isolate started with message: $message');

  // Send a message to the main isolate
  SendPort sendPort = IsolateNameServer.lookupPortByName('main');
  sendPort.send('Message from isolate!');

  // Receive a message from the main isolate
  ReceivePort receivePort = ReceivePort();
  sendPort.send(receivePort.sendPort);
  receivePort.listen((dynamic message) {
    print('Received message in isolate: $message');
  });
}

Compute:

On the other hand, Compute is a helper function provided by Flutter that simplifies running a function in a separate isolate. It is a shorthand way of creating and managing isolates without manually creating and managing them using the Isolate class. Compute takes a function as an argument and automatically creates an isolate to run that function in parallel with the UI.
The Compute function is best suited for short-lived tasks that are not computationally intensive and do not require extensive communication with the main isolate. Examples of functions that can be offloaded to Compute include sorting a list, converting data formats, or performing simple data manipulations. Compute is easy to use and provides a simple way to parallelize tasks without having to manually manage isolates, making it ideal for small to medium-sized tasks.

import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:image/image.dart' as img;

void main() async {
  File imageFile = File('image.jpg');

  // Load and process the image in a separate isolate
  img.Image processedImage = await compute(_processImage, imageFile);

  // Save the processed image to a new file
  File processedImageFile = File('processed_image.jpg');
  await processedImageFile.writeAsBytes(img.encodeJpg(processedImage));
  print('Processed image saved to: ${processedImageFile.path}');
}

img.Image _processImage(File imageFile) {
  // This is the computationally intensive task
  img.Image image = img.decodeImage(imageFile.readAsBytesSync());
  img.Image processedImage = // Perform image processing operations
  return processedImage;
}

Differences:

The main difference between Flutter Isolate and Compute is the level of control and complexity they offer. Flutter Isolate provides more fine-grained control over the creation and management of isolates, making it suitable for complex tasks that require extensive communication with the main isolate or involve multiple isolates working together. On the other hand, Compute provides a more straightforward way to offload short-lived tasks to a separate isolate, without having to manually manage isolates.
Another key difference is the level of scalability. Flutter isolate allows for creating and managing multiple isolates, making it highly scalable for applications that require parallel processing of multiple tasks. In contrast, Compute is designed for small to medium-sized tasks and provides a different level of scalability.

When to Use Each One:

Flutter isolate is generally recommended for computationally intensive tasks or tasks that require extensive communication with the main isolate, and when scalability is a concern. Use Flutter Isolate when you need fine-grained control over isolates and when you need to create and manage multiple isolates concurrently.
On the other hand, Compute is recommended for small to medium-sized tasks that are not computationally intensive and do not require extensive communication with the main isolate. Use Compute when you need a simple and easy way to offload short-lived tasks to a separate isolate without having to manually manage isolates.

In conclusion, both Flutter Isolate and Compute are powerful tools for parallel processing in Flutter applications.