SwiftTask & ReactKit benchmark test. https://github.com/ReactKit/SwiftTask/pull/22

benchmark.swift

for i in 0..<5 {
    let startTime: CFAbsoluteTime = CFAbsoluteTimeGetCurrent();
    
    for _ in 0..<100 {
        let task = Task<Float, String, NSError> { p, f, r, c in }
        //let signal = Signal<Int>.never()
    }
    
    let elapsedTime: CFAbsoluteTime = CFAbsoluteTimeGetCurrent() - startTime;
    
    println("[\(i)]: \(loop) loops = \(elapsedTime), 1 loop = \(elapsedTime/Double(loop))")
}

result.txt

(all tested on iPhone5s, with optimization level = -O) 

// SwiftTask 2.5.1
[0]: 100 loops = 1.63266599178314, 1 loop = 0.0163266599178314
[1]: 100 loops = 1.58188897371292, 1 loop = 0.0158188897371292
[2]: 100 loops = 1.57783699035645, 1 loop = 0.0157783699035645
[3]: 100 loops = 1.58536404371262, 1 loop = 0.0158536404371262
[4]: 100 loops = 1.58243000507355, 1 loop = 0.0158243000507355

// SwiftTask 2.6.0pre
[0]: 100 loops = 0.0150429606437683, 1 loop = 0.000150429606437683
[1]: 100 loops = 0.00679397583007812, 1 loop = 6.79397583007812e-05
[2]: 100 loops = 0.00657498836517334, 1 loop = 6.57498836517334e-05
[3]: 100 loops = 0.00679999589920044, 1 loop = 6.79999589920044e-05
[4]: 100 loops = 0.00672101974487305, 1 loop = 6.72101974487305e-05

(SwiftTask: 240x faster)

// ReactKit 0.5.0
[0]: 100 loops = 1.75876998901367, 1 loop = 0.0175876998901367
[1]: 100 loops = 1.73212802410126, 1 loop = 0.0173212802410126
[2]: 100 loops = 1.73549199104309, 1 loop = 0.0173549199104309
[3]: 100 loops = 1.7194259762764, 1 loop = 0.017194259762764
[4]: 100 loops = 1.73625200986862, 1 loop = 0.0173625200986862

// ReactKit 0.6.0pre
[0]: 100 loops = 0.0204319953918457, 1 loop = 0.000204319953918457
[1]: 100 loops = 0.0127019882202148, 1 loop = 0.000127019882202148
[2]: 100 loops = 0.0127049684524536, 1 loop = 0.000127049684524536
[3]: 100 loops = 0.0122619867324829, 1 loop = 0.000122619867324829
[4]: 100 loops = 0.0129290223121643, 1 loop = 0.000129290223121643

(ReactKit: 144x faster)