如何解决Swift 中的 vDSP 问题,无法对矩阵进行乘法、转置和求逆
在使用 Accelerate 的 Swift 中,我无法写出线性回归中的正态方程:(X_Transpose * X)_Inverted * X_Transpose * y。任何人都可以帮我解决我的代码有什么问题吗?
class normalEquation {
public private(set) var thetas: [Double]
init(X: [[Double]],y: [Double]) {
// Get matrix dimensions row x col
let rows = Int32(X.count)
let cols = Int32(X.first!.count)
let X_1 = X.flatMap({ $0 })
// Create X transposed
var X_T = X_1
vDSP_mtransD(X_1,vDSP_Stride(1),&X_T,vDSP_Length(cols),vDSP_Length(rows))
// Multiply X_T and X together and store it in X_I (not yet inverted)
var X_I: [Double] = Array(repeating: 0.0,count: Int(cols) * Int(cols))
vDSP_mmulD(X_T,X_1,&X_I,vDSP_Length(rows))
// Inversion of X_I in two steps
var error: Int32 = 0
var pivot: [Int32] = Array(repeating: 0,count: Int(cols))
var workspace: [Double] = Array(repeating: 0.0,count: Int(cols))
// LU Factorization
var n1: Int32 = cols,n2: Int32 = cols,n3: Int32 = cols
dgetrf_(&n1,&n2,&n3,&pivot,&error)
// Check for error
if error != 0 { fatalError() }
// Do matrix inversion
n1 = cols; n2 = cols; n3 = cols
dgetri_(&n1,&workspace,&error)
// Check for error
if error != 0 { fatalError() }
// Now multiply our inverted matrix by the transpose
var X_M = X_T
vDSP_mmulD(X_I,X_T,&X_M,vDSP_Length(rows),vDSP_Length(cols))
// Now multiply our mult matrix by y to get our final
var X_F = X_M
vDSP_mmulD(X_M,y,&X_F,vDSP_Length(rows))
self.thetas = X_F
print("Thetas: \(self.thetas)")
}
}
解决方法
没关系!找到了 Ozgur Sahin 的 AMAZING GitHub 矩阵类型代码,实际上令人难以置信,这是链接:https://github.com/hollance/Matrix/blob/master/Matrix.swift。
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