TParallel.For:在TParallel.For循环中计算值时将值存储在TList中 [英] TParallel.For: Store values in a TList while they are calculated in a TParallel.For loop
问题描述
我想使用TParallel.&For
循环来计算例如1到100000之间的质数,并将所有这些质数保存在AList: TList<Integer>
中:
I want to use a TParallel.&For
loop to calculate, for example, the prime numbers between 1 and 100000 and save all these prime numbers in AList: TList<Integer>
:
procedure TForm1.Button1Click(Sender: TObject);
var
i: Integer;
AList: TList<Integer>;
LoopResult: Tparallel.TLoopResult;
begin
AList:=TList<Integer>.Create;
TParallel.&For(1, 100000,
procedure(AIndex: Integer)
begin
if IsPrime(AIndex) then
begin
//add the prime number to AList
end;
end);
//show the list
for i := 0 to AList.Count-1 do
begin
Memo1.Lines.Add(IntToStr(AList[i]));
end;
end;
可以并行执行计算而不会出现问题,但是TList
是共享资源.如何以线程安全的方式将已确认的素数添加到列表中?
The calculations can be performed in parallel without issue but the TList
is a shared resource. How can I add confirmed primes to the list in a threadsafe way?
推荐答案
您只需调用AList.Add(AIndex)
,然后在循环结束后调用Sort()
列表即可.但是TList
不是线程安全的,因此您需要在Add()
周围加锁,例如TCriticalSection
或TMutex
:
You would simply call AList.Add(AIndex)
, and then Sort()
the list after the loop is finished. But TList
is not thread-safe, so you need a lock around the Add()
, like a TCriticalSection
or TMutex
:
procedure TForm1.Button1Click(Sender: TObject);
var
i: Integer;
AList: TList<Integer>;
ALock: TCriticalSection;
LoopResult: TParallel.TLoopResult;
begin
AList := TList<Integer>.Create;
ALock := TCriticalSection.Create;
TParallel.&For(1, 100000,
procedure(AIndex: Integer)
begin
if IsPrime(AIndex) then
begin
ALock.Enter;
try
AList.Add(AIndex);
finally
ALock.Leave;
end;
end;
end);
AList.Sort;
for i := 0 to AList.Count-1 do
begin
Memo1.Lines.Add(IntToStr(AList[i]));
end;
ALock.Free;
AList.Free;
end;
或使用TThreadList<T>
代替:
procedure TForm1.Button1Click(Sender: TObject);
var
i: Integer;
AList: TThreadList<Integer>;
LList: TList<Integer>;
LoopResult: TParallel.TLoopResult;
begin
AList := TThreadList<Integer>.Create;
TParallel.&For(1, 100000,
procedure(AIndex: Integer)
begin
if IsPrime(AIndex) then
begin
AList.Add(AIndex);
end;
end);
LList := AList.LockList;
try
LList.Sort;
for i := 0 to LList.Count-1 do
begin
Memo1.Lines.Add(IntToStr(LList[i]));
end;
finally
AList.UnlockList;
end;
AList.Free;
end;
这篇关于TParallel.For:在TParallel.For循环中计算值时将值存储在TList中的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!