Combine vs. RxSwift Performance Benchmark Test Suite 📊

This project contains a benchmarking test suite for comparing the performance of the most commonly used components and operators in RxSwift and Combine. For a detailed comparison of RxSwift with Combine have a look at our blog post.

The RxSwift performance benchmark tests are the original ones used in the RxSwift project. We removed the two tests from RxCocoa testing Drivers, since there is no equivalent in Combine. The Combine tests are 1:1 translated tests from the Rx test-suite and should, therefore, be easily comparable.

Important update: As mentioned correctly the old numbers were created with XCTests running in DEBUG mode. The differences seem not so critical in Release builds. We have updated all the numbers and graphs to use release builds.

As a summary Combine was faster in every test and on average 41% more performant than RxSwift. These statistics show every test-method and its results. Lower is better.

Test Results Summary

Test	RxSwift (ms)	Combine (ms)	Factor
PublishSubjectPumping	227	135	168%
PublishSubjectPumpingTwoSubscriptions	400	246	163%
PublishSubjectCreating	295	250	118%
MapFilterPumping	123	132	93%
MapFilterCreating	168	114	147%
FlatMapsPumping	646	367	176%
FlatMapsCreating	214	121	177%
FlatMapLatestPumping	810	696	116%
FlatMapLatestCreating	263	180	146%
CombineLatestPumping	298	282	106%
CombineLatestCreating	644	467	138%

Testing Details

Machine: MacBook Pro 2018, 2,7 GHz Intel Core i7, 16 GB IDE: Xcode 11.0 beta 5 (11M382q) Testing Device: iPhone XR Simulator

Performance Test Example: PublishSubject Pumping

For every test we replace the RxSwift component with the corresponding Combine component. In this case PublishSubject with PassthroughSubject.

RxSwift

func testPublishSubjectPumping() {
    measure {
        var sum = 0
        let subject = PublishSubject<Int>()

        let subscription = subject
            .subscribe(onNext: { x in
                sum += x
            })

        for _ in 0 ..< iterations * 100 {
            subject.on(.next(1))
        }

        subscription.dispose()

        XCTAssertEqual(sum, iterations * 100)
    }
}

Combine

func testPublishSubjectPumping() {
    measure {
        var sum = 0
        let subject = PassthroughSubject<Int, Never>()

        let subscription = subject
            .sink(receiveValue: { x in
                sum += x
            })

        for _ in 0 ..< iterations * 100 {
            subject.send(1)
        }
        
        subscription.cancel()
        
        XCTAssertEqual(sum, iterations * 100)
    }
}

Detailed Performance Test Results: RxSwift vs. Combine

PublishSubjectPumping

PublishSubjectPumpingTwoSubscriptions

PublishSubjectCreating

MapFilterPumping

MapFilterCreating

FlatMapsPumping

FlatMapsCreating

FlatMapLatestPumping

FlatMapLatestCreating

CombineLatestPumping

CombineLatestCreating