我必须通过字符串比较在758.000个地址的列表中找到重复的地址。到目前为止,我已经完成了什么:
public int StartDuplicateFinder(List<Address> addresses, List<Address> checklist)
{
int found = 0;
foreach(Address addr1 in addresses)
{
List<Address> addresses2 = checklist.FindAll(
delegate (Address addr2)
{
return addr2.AddressString == addr1.AddressString && addr2.Duplicate == ""
&& addr2.AddrIndex > addr1.AddrIndex;
}
);
foreach(Address addr2 in addresses2)
{
addr2.Duplicate = "1";
found++;
}
}
return found;
}
这大约需要7个小时(太长),并且可以提供大约93.000个重复!
[为了加快速度,我将checklist
分成4部分(200k,200k,200k和158k)并使用List<Address> checklists
像这样:Task
:
public class Worker
{
private List<Address> addresses = null;
private List<Addresses> checklist = null
private int found = 0;
public Worker(List<Address> _addresses, List<Address> _checklist)
{
addresses = _addresses; //always 758.000 addresses
//with 4 Tasks: Task 1, 2 and 3 = 200.000 addresses, Task 4 = 158.000 addresses
//with 6 Tasks: Task 1, 2, 3, 4 and 5 with 150.000 addresses, Task 6 with 8.000 addresses
checklist = _checklist;
}
public int StartDuplicateFinder()
{
foreach(Address addr1 in addresses)
{
List<Address> addresses2 = checklist.FindAll(
delegate (Address addr2)
{
return addr2.AddressString == addr1.AddressString && addr2.Duplicate == ""
&& addr2.AddrIndex > addr1.AddrIndex;
}
);
foreach(Address addr2 in addresses2)
{
addr2.Duplicate = "1";
found++;
}
}
}
public int Found {get {return found;}}
}
private async void StartTasks(List<Task> Tasklist)
{
foreach (Task t in Tasklist)
{
t.Start();
}
await Task.WhenAll(Tasklist.ToArray());
}
private void DoSomething()
{
List<Task> Tasklist = new List<Task>();
foreach(List<Address> checklist in checklists)
{
Worker w = new Worker(addresses, checklist);
Tasklist.Add(new Task(StartDuplicateFinder));
}
StartTasks(Tasklist);
//wait until the tasks are finished
//do other stuff
...
}
现在它只运行35分钟!但是,如果我查看发现的重复项,就会有很大的偏差。仅发现约27.000个重复项。
我尝试了几次,每次得到其他结果。
4 Tasks, first run: 4 Tasks, second run:
Task# > duplicates Task# > duplicates
1 > 749 1 > 689
2 > 2450 2 > 2391
3 > 10304 3 > 10073
4 > 14462 4 > 14282
Sum > 27965 Sum > 27435
6 Tasks, first run: 6 Tasks, second run:
Task# > duplicates Task# > duplicates
1 > 16 1 > 24
2 > 56 2 > 55
3 > 202 3 > 236
4 > 679 4 > 634
5 > 852 5 > 800
6 > 2985 6 > 2981
Sum > 4790 Sum > 4730
每次都是758.000个地址的相同列表。
我用Task
,Thread
和BackgroundWorker
尝试过,但是我总是得到不同的结果!如果我在1 Task中运行此命令,则结果始终是92.377个重复项(我认为这是正确的)。
有人可以帮助我解决问题吗?
问题中没有足够的代码来推测。如果您真的要进行故障排除,则需要一个完整的,独立的存储库。但是,这种行为的典型原因是您正在多个线程中修改共享数据。根据经验,并行工作人员应处理只读数据,并返回其结果以由主线程累加。
但是要考虑使用更有效的数据结构和算法,而不是并行处理。 IE(而不是嵌套循环)联接,请构建哈希表(Dictionary<TKey,TValue>
或Lookup<TKey,TValue>
)以使其在单个线程上更快(至少作为第一步)。 EG之类的东西:
public int StartDuplicateFinder(List<Address> addresses, List<Address> checklist)
{
int found = 0;
var checklistByAddressString = checklist.ToLookup(a => a.AddressString, a => a);
foreach (Address addr1 in addresses)
{
var addressMatches = checklistByAddressString[addr1.AddressString];
var addresses2 = addressMatches.Where(addr2 => addr2.Duplicate == ""
&& addr2.AddrIndex > addr1.AddrIndex);
foreach (Address addr2 in addresses2)
{
addr2.Duplicate = "1";
found++;
}
}
return found;
}
问题是您正在循环浏览addresses
列表中的项目。您正在创建比赛条件。
您的过滤器具有,作为条件的一部分:
addr2.Duplicate == ""
稍后您更改项目:
addr2.Duplicate = "1"`.
也许最好对addresses
进行分块,然后对完整的checkList
不利
或者,仅对两个列表在单线程上使用LINQ query
。您很可能会获得更快的结果,然后手动遍历集合。