class CustomData
{
public int TNum;
public int TResult;
}
public static int F_recursion(int n, int w)
{
if (n == 0 || w == 0)
return 0;
else if (s[n] > w)
return F_recursion(n - 1, w);
else
{
return Math.Max(F_recursion(n - 1, w),
p[n] + F_recursion(n - 1, w - s[n]));
}
}
public static int F_recursion2(int n, int w)
{
int numba = 0;
int countCPU = 8;
Task[] tasks = new Task[countCPU];
for (var j = 0; j < countCPU; j++)
tasks[j] = Task.Factory.StartNew(
(object p) =>
{
var data = p as CustomData; if (data == null) return;
data.TResult = F_recursion(n - data.TNum, w);
},
new CustomData() { TNum = j });
Task.WaitAll(tasks);
numba = (tasks[0].AsyncState as CustomData).TResult
+ (tasks[1].AsyncState as CustomData).TResult
+ (tasks[2].AsyncState as CustomData).TResult
+ (tasks[3].AsyncState as CustomData).TResult;
return numba;
}
如何使F_recursion2方法并行工作?使用我的代码当前结果是
Time in milliseconds for recursion: 1,075
recursion( 150 ) = 7,237
Time in milliseconds for parallel recursion: 1,581
recursion( 150 ) = 28,916
如您所见,并行方法打印的数字是其 4 倍,并且需要更多时间来计算,这没有意义。我怎样才能解决递归并行工作的问题?
编辑 更改为Parallel.For
循环,结果仍然与上面相同。
public static int F_recursion2(int n, int w)
{
int numba = 0;
int countCPU = 8;
Task[] tasks = new Task[countCPU];
Parallel.For(0, countCPU, j =>
{
tasks[j] = Task.Factory.StartNew(
(object p) =>
{
var data = p as CustomData; if (data == null) return;
data.TResult = F_recursion(n - data.TNum, w);
},
new CustomData() { TNum = j });
});
Task.WaitAll(tasks);
numba = (tasks[0].AsyncState as CustomData).TResult
+ (tasks[1].AsyncState as CustomData).TResult
+ (tasks[2].AsyncState as CustomData).TResult
+ (tasks[3].AsyncState as CustomData).TResult;
return numba;
}
我想
到的解决方案是使用Parallel.For
。为此,您应该使用 Parallel.For
实现for
。要查看示例,请访问此处。