C#•3y ago

Getting the result from a list of tasks

Its been a minute since I have done async methods but i know i can do a list of tasks I just think I'm using them wrong.

const double LAT_MIN = 37.70649; //y
const double LAT_MAX = 37.77436;
const double LON_MAX = -85.95120;
const double LON_MIN = -85.86829;

List<Task> tasks = new List<Task>();
List<Point> points = new List<Point>();

for (double i = LAT_MIN; i < LAT_MIN; i += .00005)
{
    tasks.Add(CreatePointsAsync(i));
}
foreach (Task task in tasks)
    task.Start();

Task.WhenAll(tasks).Wait();
foreach(Task<List<Point>> task in tasks)
{
    points.InsertRange(points.Count, task.Result);
}

foreach(Point point in points)
{
    Console.WriteLine(point.X + " " + point.Y);
}

async Task<List<Point>> CreatePointsAsync(double y)
{
    List<Point> value = new List<Point>();
    for (double i = LON_MIN; i < LON_MAX; i += .00005)
    {
        value.Add(new Point(i, y));
    }
    return value;
}

public struct Point
{
    public double X;
    public double Y;

    public Point(double X, double Y)
    {
        this.X = X;
        this.Y = Y;
    }
};

const double LAT_MIN = 37.70649; //y
const double LAT_MAX = 37.77436;
const double LON_MAX = -85.95120;
const double LON_MIN = -85.86829;

List<Task> tasks = new List<Task>();
List<Point> points = new List<Point>();

for (double i = LAT_MIN; i < LAT_MIN; i += .00005)
{
    tasks.Add(CreatePointsAsync(i));
}
foreach (Task task in tasks)
    task.Start();

Task.WhenAll(tasks).Wait();
foreach(Task<List<Point>> task in tasks)
{
    points.InsertRange(points.Count, task.Result);
}

foreach(Point point in points)
{
    Console.WriteLine(point.X + " " + point.Y);
}

async Task<List<Point>> CreatePointsAsync(double y)
{
    List<Point> value = new List<Point>();
    for (double i = LON_MIN; i < LON_MAX; i += .00005)
    {
        value.Add(new Point(i, y));
    }
    return value;
}

public struct Point
{
    public double X;
    public double Y;

    public Point(double X, double Y)
    {
        this.X = X;
        this.Y = Y;
    }
};

I need to create a lot of points so i wanted to split it up to make it faster

13 Replies

FacePalmGamerOP•3y ago

so dies it return the value of all the tasks i have running? because doing var test = Task.WhenAll(tasks); says test is just a task not a array of any sort

phaseshift•3y ago

The value is in the individual task Which, btw, create points async is synchronous

FacePalmGamerOP•3y ago

what am i doing wrong, i thought if it was async and you ran it on a task it ran in a different thread

phaseshift•3y ago

Common misconception You don't have any awaits in your async method, so it will just be synchronous If you need to run CPU heavy code in a thread, use Task.Run

FacePalmGamerOP•3y ago

can i just add an await before the return?

phaseshift•3y ago

If you added an await as the first line that would work. Just before the return... Nope

FacePalmGamerOP•3y ago

how do i do it your way, with just Task.Run assume that is the way I'm supposed to do something like this

phaseshift•3y ago

Change the create points method to just return a list of point, no async or task

FacePalmGamerOP•3y ago

tasks.Add(Task.Run(() => CreatePoints(i)));?

phaseshift•3y ago

Yes

FacePalmGamerOP•3y ago

or am i not adding them to a list anymore either ok cool ok so its not giving me anything. like its not running at all since its finishes instantly

const double LAT_MIN = 37.70649; //y
const double LAT_MAX = 37.77436;
const double LON_MAX = -85.95120;
const double LON_MIN = -85.86829;

List<Task<List<Point>>> tasks = new List<Task<List<Point>>>();
List<Point> points = new List<Point>();

for (double i = LAT_MIN; i < LAT_MIN; i += .00005)
{
    tasks.Add(Task.Run(() => CreatePoints(i)));
}

var results = await Task.WhenAll(tasks);
foreach (List<Point> result in results)
{
    points.InsertRange(points.Count, result);
}

foreach (Point point in points)
{
    Console.WriteLine(point.X + " " + point.Y);
}

Console.WriteLine("fin");

List<Point> CreatePoints(double y)
{
    List<Point> value = new List<Point>();
    for (double i = LON_MIN; i < LON_MAX; i += .00005)
    {
        value.Add(new Point(i, y));
    }
     return value;
}

public struct Point
{
    public double X;
    public double Y;

    public Point(double X, double Y)
    {
        this.X = X;
        this.Y = Y;
    }
};

const double LAT_MIN = 37.70649; //y
const double LAT_MAX = 37.77436;
const double LON_MAX = -85.95120;
const double LON_MIN = -85.86829;

List<Task<List<Point>>> tasks = new List<Task<List<Point>>>();
List<Point> points = new List<Point>();

for (double i = LAT_MIN; i < LAT_MIN; i += .00005)
{
    tasks.Add(Task.Run(() => CreatePoints(i)));
}

var results = await Task.WhenAll(tasks);
foreach (List<Point> result in results)
{
    points.InsertRange(points.Count, result);
}

foreach (Point point in points)
{
    Console.WriteLine(point.X + " " + point.Y);
}

Console.WriteLine("fin");

List<Point> CreatePoints(double y)
{
    List<Point> value = new List<Point>();
    for (double i = LON_MIN; i < LON_MAX; i += .00005)
    {
        value.Add(new Point(i, y));
    }
     return value;
}

public struct Point
{
    public double X;
    public double Y;

    public Point(double X, double Y)
    {
        this.X = X;
        this.Y = Y;
    }
};

phaseshift•3y ago

Look at your first for loop

FacePalmGamerOP•3y ago

ah yeah that will do it

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Getting the result from a list of tasks