mergesort.cs

        private void ParallelSort<T>(List<T> list, Comparer<T> comparer) {
            void MergeSort(List<T> l, Comparer<T> comp, int low, int high) {
                int mid = (high - low) / 2;
                var t1 = new Thread(() => MergeSort(l, comp, low, mid));
                t1.Start();
                t1.Join();
                MergeSort(l, comp, mid, high);
                Merge(l, comp, low, mid, high);
            }

            void Merge(List<T> l, Comparer<T> comp, int low, int mid, int high) {
                var copy = l.GetRange(low, high - low);
                int i = low;
                while (i < mid && i + mid < high) {
                    l[i++] = comp.Compare(copy[low], copy[mid]) < 0 ? copy[low++] : copy[mid++];
                }
                while (i < mid) {
                    l[i++] = copy[low++];
                }
                while (mid < high) {
                    l[i++] = copy[mid++];
                }
            }

            MergeSort(list, comparer, 0, list.Count);
        }