Parallel的陷阱

var nums = Enumerable.Range(1,4).ToArray();
            int total = 0;
            Parallel.For<int>(
                fromInclusive: 0,
                toExclusive: nums.Length,
                /* 陷阱 */
                localInit: () => 1,
                body: (i, loopState, subtotal) =>
                {
                    return subtotal + nums[i];
                },
                localFinally: i => Interlocked.Add(ref total, i)
                );
            Console.WriteLine("total={0}",total);