Data commit

Task/Cholesky-decomposition/Swift/cholesky-decomposition.swift

@@ -0,0 +1,50 @@
+func cholesky(matrix: [Double], n: Int) -> [Double] {
+  var res = [Double](repeating: 0, count: matrix.count)
+
+  for i in 0..<n {
+    for j in 0..<i+1 {
+      var s = 0.0
+
+      for k in 0..<j {
+        s += res[i * n + k] * res[j * n + k]
+      }
+
+      if i == j {
+        res[i * n + j] = (matrix[i * n + i] - s).squareRoot()
+      } else {
+        res[i * n + j] = (1.0 / res[j * n + j] * (matrix[i * n + j] - s))
+      }
+    }
+  }
+
+  return res
+}
+
+func printMatrix(_ matrix: [Double], n: Int) {
+  for i in 0..<n {
+    for j in 0..<n {
+      print(matrix[i * n + j], terminator: " ")
+    }
+
+    print()
+  }
+}
+
+let res1 = cholesky(
+  matrix: [25.0, 15.0, -5.0,
+           15.0, 18.0,  0.0,
+           -5.0,  0.0, 11.0],
+  n: 3
+)
+
+let res2 = cholesky(
+  matrix: [18.0, 22.0,  54.0,  42.0,
+           22.0, 70.0,  86.0,  62.0,
+           54.0, 86.0, 174.0, 134.0,
+           42.0, 62.0, 134.0, 106.0],
+  n: 4
+)
+
+printMatrix(res1, n: 3)
+print()
+printMatrix(res2, n: 4)