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;
}
How could i make F_recursion2 method to work in parallel? With my code current results are
Time in milliseconds for recursion: 1,075
recursion( 150 ) = 7,237
Time in milliseconds for parallel recursion: 1,581
recursion( 150 ) = 28,916
As you can see parallel approach prints 4 times bigger number and it takes more time to compute which doesn't make sense. How could I approach this problem that recursion would work in parallel?
EDIT Changed for loop to Parallel.For still same results as above.
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;
}
On solution which comes to my mind is using Parallel.For
. To do this, you should just implement the for
using Parallel.For
. To see an example, visit here .
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.