我不确定这是否可行,但如果可行,我可能做得不对。假设我有一个链接到许多消费者(ActionBlocks)的共享缓冲区。每个消费者都应该消费满足用于将其链接到缓冲区的谓词的数据。例如,ActionBlock1 应该消耗满足 x => x % 5 == 0
的数字, ActionBlock2 应该只消耗 x => x % 5 == 1
等等
这是我得到的:
private static ITargetBlock<int> BuildPipeline(int NumProductionLines)
{
var productionQueue = new BufferBlock<int>();
for (int i = 0; i < NumProductionLines; i++)
{
ActionBlock<int> productionLine = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", i + 1, num));
productionQueue.LinkTo(productionLine, x => x % NumProductionLines == i);
}
return productionQueue;
}
然后我调用:
Random rnd = new Random();
ITargetBlock<int> temp = BuildPipeline(5);
while (true)
{
temp.Post(rnd.Next(255));
}
但是这不起作用。控制台中不显示任何输出。如果我修改 BuildPipeline
方法为:
private static ITargetBlock<int> BuildPipeline(int NumProductionLines)
{
var productionQueue = new BufferBlock<int>();
ActionBlock<int> productionLine1 = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", 1, num));
ActionBlock<int> productionLine2 = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", 2, num));
ActionBlock<int> productionLine3 = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", 3, num));
ActionBlock<int> productionLine4 = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", 4, num));
ActionBlock<int> productionLine5 = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", 5, num));
productionQueue.LinkTo(productionLine1, x => x % 5 == 0);
productionQueue.LinkTo(productionLine2, x => x % 5 == 1);
productionQueue.LinkTo(productionLine3, x => x % 5 == 2);
productionQueue.LinkTo(productionLine4, x => x % 5 == 3);
productionQueue.LinkTo(productionLine5, x => x % 5 == 4);
return productionQueue;
}
代码执行预期的操作。
有人可以阐明为什么动态创建和链接操作 block 不起作用吗?
附言如果我在 ITargetBlock<int> temp = BuildPipeline(5);
之后立即进入代码temp 确实显示有 5 个目标链接到缓冲区。而且每个target的Id都不一样。
提前致谢
编辑:添加了 svick 建议的更改,但仍然不好:
private static ITargetBlock<int> BuildPipeline(int NumProductionLines)
{
var productionQueue = new BufferBlock<int>();
var opt = new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 1 };
for (int i = 0; i < NumProductionLines; i++)
{
ActionBlock<int> productionLine = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", i + 1, num));
int j = i;
productionQueue.LinkTo(productionLine, x => x % NumProductionLines == j);
}
ActionBlock<int> discardedLine = new ActionBlock<int>(num => Console.WriteLine("Discarded: {0}", num));
productionQueue.LinkTo(discardedLine);
return productionQueue;
}
现在只有第二条生产线处理数据(满足 x % 5 == 1 谓词的一条)。并且数据不满足谓词,这意味着我得到以 9 和 7 结尾的数字。
编辑:工作代码如下所示:
private static ITargetBlock<int> BuildPipeline(int NumProductionLines)
{
var productionQueue = new BufferBlock<int>();
var opt = new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 1 };
for (int i = 0; i < NumProductionLines; i++)
{
int j = i;
ActionBlock<int> productionLine = new ActionBlock<int>(num => Console.WriteLine("Processed by line {0}: {1}", j + 1, num));
productionQueue.LinkTo(productionLine, x => x % NumProductionLines == j);
}
productionQueue.LinkTo(DataflowBlock.NullTarget<int>());
return productionQueue;
}
最佳答案
问题是在您的第一个版本中,您对每个目标 block 使用相同的谓词。换句话说,谓词不依赖于 i
。
但即使这样做了,您的代码也不会工作,因为 i
变量在谓词之间共享,因此它们都将使用最后一个值。解决方法是将 i
复制到局部变量中并在谓词中使用它。
代码可能是这样的:
private static ITargetBlock<int> BuildPipeline(int NumProductionLines)
{
var productionQueue = new BufferBlock<int>();
for (int i = 0; i < NumProductionLines; i++)
{
int iCopy = i;
ActionBlock<int> productionLine = new ActionBlock<int>(
num => Console.WriteLine("Processed by line {0}: {1}", iCopy + 1, num));
productionQueue.LinkTo(
productionLine, x => x % NumProductionLines == iCopy);
}
return productionQueue;
}
如果您问为什么您的代码不至少处理 x % 5 == 1
个数字,那是因为随机生成器可能会生成一个与该谓词不匹配的数字, 所以没有一个 ActionBlock
会接受它。因此,该号码将留在源 block 的输出队列中,其他号码将无法通过。
如果在您的实际代码中可能会发生类似情况,并且您想丢弃所有不符合任何谓词的数字,您可以将源代码块链接到 a block that does nothing并在将其链接到所有有用的 block 之后接受任何内容:
productionQueue.LinkTo(DataflowBlock.NullTarget<int>());
关于c# - 将动态创建的 ActionBlock 链接到 BufferBlock,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12647185/