WindArrayPerformanceTests

// Tests for post: http://chchrn.com/2021/09/19/vdsp_for_wind.html
// CHCHRN

import XCTest
import Accelerate

final class ArrayTransformer {

    func floatArray(intValues: [UInt8],
                    min: Float,
                    max: Float) -> [Float] {
        let step = (max - min) / 256
        let result = intValues.map { (v: UInt8) -> Float in
            return Float(v) * step + min
        }
        return result
    }
}

final class DSPTransformer {

    func floatArray(intValues: [UInt8],
                    min: Float,
                    max: Float) -> [Float] {
        var step = (max - min) / 256
        let count = intValues.count
        let stride = vDSP_Stride(1)
        let n = vDSP_Length(count)

        var fltArray = [Float](repeating: 0, count: count)
        vDSP_vfltu8(intValues, stride,
                    &fltArray, stride,
                    n)

        var mulArray = [Float](repeating: 0, count: count)
        vDSP_vsmul(fltArray, stride,
                   &step,
                   &mulArray, stride,
                   n)

        var mMin = min
        var result = [Float](repeating: 0, count: count)
        vDSP_vsadd(mulArray, stride,
                   &mMin,
                   &result, stride,
                   n)
        return result
    }
}



class WindArrayPerformanceTest: XCTestCase {
    private var min: Float!
    private var max: Float!
    private var uint8Values: [UInt8] = [UInt8]()

    override func setUp() {
        self.min = 10
        self.max = 90
        let count = 2000 * 2000
        let uint8Range = (0..<UInt8.max)
        self.uint8Values = (0..<count).map { _ in uint8Range.randomElement()! }
    }

    func testSwiftArrayPerformance() {
        var floatValues = [Float]()
        let transformer = ArrayTransformer()
        self.measure {
            floatValues = transformer.floatArray(intValues: self.uint8Values,
                                                 min: self.min,
                                                 max: self.max)
        }
        print("\(floatValues.count)")
    }

    func testDSPPerformance() {
        var floatValues = [Float]()
        let transformer = DSPTransformer()
        self.measure {
            floatValues = transformer.floatArray(intValues: self.uint8Values,
                                                 min: self.min,
                                                 max: self.max)
        }
        print("\(floatValues.count)")
    }
}