Family Day update

Task/Parallel-calculations/Swift/parallel-calculations.swift

@@ -0,0 +1,74 @@
+import BigInt
+import Foundation
+
+extension BinaryInteger {
+  @inlinable
+  public func primeDecomposition() -> [Self] {
+    guard self > 1 else { return [] }
+
+    func step(_ x: Self) -> Self {
+      return 1 + (x << 2) - ((x >> 1) << 1)
+    }
+
+    let maxQ = Self(Double(self).squareRoot())
+    var d: Self = 1
+    var q: Self = self & 1 == 0 ? 2 : 3
+
+    while q <= maxQ && self % q != 0 {
+      q = step(d)
+      d += 1
+    }
+
+    return q <= maxQ ? [q] + (self / q).primeDecomposition() : [self]
+  }
+}
+
+let numbers = [
+  112272537195293,
+  112582718962171,
+  112272537095293,
+  115280098190773,
+  115797840077099,
+  1099726829285419,
+  1275792312878611,
+  BigInt("64921987050997300559")
+]
+
+func findLargestMinFactor<T: BinaryInteger>(for nums: [T], then: @escaping ((n: T, factors: [T])) -> ()) {
+  let waiter = DispatchSemaphore(value: 0)
+  let lock = DispatchSemaphore(value: 1)
+  var factors = [(n: T, factors: [T])]()
+
+  DispatchQueue.concurrentPerform(iterations: nums.count) {i in
+    let n = nums[i]
+
+    print("Factoring \(n)")
+
+    let nFacs = n.primeDecomposition().sorted()
+
+    print("Factored \(n)")
+
+    lock.wait()
+    factors.append((n, nFacs))
+
+    if factors.count == nums.count {
+      waiter.signal()
+    }
+
+    lock.signal()
+  }
+
+  waiter.wait()
+
+  then(factors.sorted(by: { $0.factors.first! > $1.factors.first! }).first!)
+}
+
+findLargestMinFactor(for: numbers) {res in
+  let (n, factors) = res
+
+  print("Number with largest min prime factor: \(n); factors: \(factors)")
+
+  exit(0)
+}
+
+dispatchMain()