1
我正在玩弄LINQ,並提出了以下利用C#Monadic語法編寫鎖的想法。這看起來太簡單了,所以我想讓我把它發佈到StackOverflow上,看看有沒有人可以很快地發現這種方法的任何主要問題。使用LINQ的可組合的鎖。任何人都可以看到這個問題嗎?
如果你在原子實現中註釋鎖,你會看到賬戶被破壞。
這個想法是關於能夠在沒有明確鎖定的情況下撰寫賬戶操作。
using System;
using System.Collections.Generic;
using System.Linq;
namespace AtomicLinq
{
public static class AccountCombinators
{
public static IAtomic <Unit> TransferAndReverse(this Account accA,
Account accB,
double amount)
{
return from a in accA.TransferTo(accB, amount)
from b in accB.TransferTo(accA, amount)
select new Unit();
}
public static IAtomic<Unit> TransferTo(this Account accA,
Account accB,
double amount)
{
return from a in accA.Withdraw(amount)
from b in accB.Deposit(amount)
select new Unit();
}
public static IAtomic<double> Withdraw(this Account acc, double amount)
{
return Atomic.Create(() => acc.Amount -= amount);
}
public static IAtomic<double> Deposit(this Account acc, double amount)
{
return Atomic.Create(() => acc.Amount += amount);
}
}
static class Program
{
static void Main(string[] args)
{
var accA = new Account("John") { Amount = 100.0 };
var accB = new Account("Mark") { Amount = 200.0 };
var syncObject = new object();
Enumerable.Range(1, 100000).AsParallel().Select(_ => accA.TransferAndReverse(accB, 100).Execute(syncObject)).Run();
Console.WriteLine("{0} {1}", accA, accA.Amount);
Console.WriteLine("{0} {1}", accB, accB.Amount);
Console.ReadLine();
}
}
public class Account
{
public double Amount { get; set; }
private readonly string _name;
public Account(string name)
{
_name = name;
}
public override string ToString()
{
return _name;
}
}
#region Atomic Implementation
public interface IAtomic<T>
{
T Execute(object sync);
}
public static class Atomic
{
public static IAtomic<T> Create<T>(Func<object, T> f)
{
return new AnonymousAtomic<T>(f);
}
public static IAtomic<T> Create<T>(Func<T> f)
{
return Create(_ => f());
}
public static IAtomic<T> Aggregate<T>(this IEnumerable<IAtomic<T>> xs)
{
return xs.Aggregate((x, y) => from a in x
from b in y
select b);
}
public static IAtomic<K> SelectMany<T, V, K>(this IAtomic<T> m, Func<T, IAtomic<V>> f, Func<T, V, K> p)
{
return Create(sync =>
{
var t = m.Execute(sync);
var x = f(t);
return p(t, x.Execute(sync));
});
}
}
public class AnonymousAtomic<T> : IAtomic<T>
{
private readonly Func<object, T> _func;
public AnonymousAtomic(Func<object, T> func)
{
_func = func;
}
public T Execute(object sync)
{
lock (sync) // Try to comment this lock you'll see that the accounts get corrupted
return _func(sync);
}
}
#endregion Atomic Implementation
}
你可以嘗試張貼codereview.stackexchange – flesh 2011-02-16 20:53:31
我只是做了。謝謝 – Holoed 2011-02-16 21:08:46