C#•3y ago

❔ Task.WhenAll does not work without Task.Run inside

Inside a task, _pathFinder.FindPath is not called. returnFirstPath is false (Task.WhenAll) but if I change list.Add(new Task<PathResult>(action)); to list.Add(Task.Run(action));, it works. Another question, I should use Task.Run to be sure it runs in different threads and get results faster?

    for (var j = 0; j < roadPoints.Length; j++)
                {
                    var j1 = j;
                    Func<PathResult> action = () =>
                    {
                        var pathResult = _pathFinder.FindPath
                        (
                            sourcePoint,
                            setting.SearchRange,
                            roadPoints[j1],
                            CheckTarget,
                            CheckObstacle,
                            ComputeWeight
                        );
                        return pathResult;
                    };
                    list.Add(new Task<PathResult>(action));
                }

                PathResult pathResult;
                if (returnFirstPath)
                {
                    pathResult = await await Task.WhenAny(list);
                }
                else
                {
                    var pathResults = await Task.WhenAll(list);
                    pathResult = pathResults.MinBy(p => p.Path.Length);
                }

    for (var j = 0; j < roadPoints.Length; j++)
                {
                    var j1 = j;
                    Func<PathResult> action = () =>
                    {
                        var pathResult = _pathFinder.FindPath
                        (
                            sourcePoint,
                            setting.SearchRange,
                            roadPoints[j1],
                            CheckTarget,
                            CheckObstacle,
                            ComputeWeight
                        );
                        return pathResult;
                    };
                    list.Add(new Task<PathResult>(action));
                }

                PathResult pathResult;
                if (returnFirstPath)
                {
                    pathResult = await await Task.WhenAny(list);
                }
                else
                {
                    var pathResults = await Task.WhenAll(list);
                    pathResult = pathResults.MinBy(p => p.Path.Length);
                }

30 Replies

Unknown User•3y ago

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GladiatorOP•3y ago

Yes, I said Task.Run is OK but without it, it is not called at all Using await await for Task.WhenAny because it returns Task<Task<>>

Unknown User•3y ago

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GladiatorOP•3y ago

list.Add(new Task<PathResult>(action)); It is I want to know if I can use Task.WhenAll without Task.Run or not, surely I should be able to use it with simple tasks

Unknown User•3y ago

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GladiatorOP•3y ago

I have tested, my above code is not called . I have put break points here var pathResult = _pathFinder.FindPath

Unknown User•3y ago

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MODiX•3y ago

tebeco#0205

REPL Result: Success

var roadPoints = new int[] { 1, 2 };
var tasks = roadPoints.Select(roadPoint =>
{
  var isThatActuallyNeeded = roadPoint;
  return Task.Run(() =>
  {
    return isThatActuallyNeeded * 100;
  });
}).ToArray();

await Task.WhenAll(tasks);
(tasks[0].Result, tasks[1].Result)

var roadPoints = new int[] { 1, 2 };
var tasks = roadPoints.Select(roadPoint =>
{
  var isThatActuallyNeeded = roadPoint;
  return Task.Run(() =>
  {
    return isThatActuallyNeeded * 100;
  });
}).ToArray();

await Task.WhenAll(tasks);
(tasks[0].Result, tasks[1].Result)

Result: ValueTuple<int, int>

{
  "item1": 100,
  "item2": 200
}

{
  "item1": 100,
  "item2": 200
}

Compile: 639.115ms | Execution: 99.819ms | React with ❌ to remove this embed.

GladiatorOP•3y ago

😐

Unknown User•3y ago

Message Not Public

MODiX•3y ago

tebeco#0205

REPL Result: Failure

var roadPoints = new int[] { 1, 2 };
var tasks = roadPoints.Select(roadPoint =>
{
  var isThatActuallyNeeded = roadPoint;
  Task.Run(() =>
  {
    return isThatActuallyNeeded * 100;
  });
}).ToArray();

await Task.WhenAll(tasks);
(tasks[0].Result, tasks[1].Result)

var roadPoints = new int[] { 1, 2 };
var tasks = roadPoints.Select(roadPoint =>
{
  var isThatActuallyNeeded = roadPoint;
  Task.Run(() =>
  {
    return isThatActuallyNeeded * 100;
  });
}).ToArray();

await Task.WhenAll(tasks);
(tasks[0].Result, tasks[1].Result)

Exception: CompilationErrorException

- The type arguments for method 'Enumerable.Select<TSource, TResult>(IEnumerable<TSource>, Func<TSource, TResult>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

- The type arguments for method 'Enumerable.Select<TSource, TResult>(IEnumerable<TSource>, Func<TSource, TResult>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

Compile: 638.056ms | Execution: 0.000ms | React with ❌ to remove this embed.

Unknown User•3y ago

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GladiatorOP•3y ago

What a terrible design It gets Task but it does not work, really shit design OK, thanks dudes

Unknown User•3y ago

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GladiatorOP•3y ago

If I call Start, it works. Yes, those tasks are required to be started Appreciated

Unknown User•3y ago

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GladiatorOP•3y ago

Now, it is like Task.Run in terms of multi threading? it can be executed in different threads or awesome

Unknown User•3y ago

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GladiatorOP•3y ago

OK, I test it By the way, in my testing Task.Run is handling it very well 10 tasks around 100 sec but now it is 11 sec

Unknown User•3y ago

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GladiatorOP•3y ago

Yes, faster is better 🙂

Unknown User•3y ago

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GladiatorOP•3y ago

Because, sometimes a path can take huge time

Unknown User•3y ago

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GladiatorOP•3y ago

Maybe, but I am tireddd It is A* algorithm path finding with large path length

Unknown User•3y ago

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mtreit•3y ago

I'm not aware of such a thing.

GladiatorOP•3y ago

At least, I can run the algorithm with each target point parallelly. It is my first simplest option

Unknown User•3y ago

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Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Task.WhenAll does not work without Task.Run inside