How to calculate percent completion in parallel?

Question

With the forcalculation of percent completion, it's easy:

for (int i = 0; i < 10; i++)
{
    for (int j = 0; j < 10; j++)
    {
        // Do somethings...
        Console.WriteLine("{0}% Done!", i * 10 + j + 1);
    }
}

Output:

1% Done!
2% Done!
3% Done!
4% Done!
5% Done!
6% Done!
7% Done!
8% Done!
9% Done!
10% Done!
11% Done!
12% Done!
13% Done!
...
93% Done!
94% Done!
95% Done!
96% Done!
97% Done!
98% Done!
99% Done!
100% Done!

---

But I have no idea about the calculated percent completion with Parallel.For:

Parallel.For(0, 10, i =>
{
    Parallel.For(0, 10, j =>
    {
        // Do somethings...
        Console.WriteLine("{0}% Done!", i * 10 + j + 1);
    });
});

Output:

1% Done!
2% Done!
3% Done!
51% Done!
52% Done!
53% Done!
54% Done!
55% Done!
56% Done!
57% Done!
58% Done!
59% Done!
60% Done!
4% Done!
5% Done!
6% Done!
...
69% Done!
70% Done!
71% Done!
72% Done!
73% Done!
74% Done!
75% Done!
76% Done!
77% Done!
78% Done!
79% Done!
80% Done!
36% Done!
37% Done!
38% Done!
39% Done!
40% Done!
35% Done!

The output does not display the correct completion percentage.

How to calculate completion percentage in Parallel.Forwithout compromising performance?

Answer 1

To do this, you can use the method Interlocked.Increment:

int progress = 0;
Parallel.For(0, 10, i =>
{
    Parallel.For(0, 10, j =>
    {
        // Do somethings...
        Console.WriteLine("{0}% Done!", Interlocked.Increment(ref progress));
    });
});

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Answer 2

, , 100 , , () :

int progress = 0;
Parallel.For(0, 10, i =>
{
    Parallel.For(0, 10, j =>
    {
        // Do somethings...
        Console.WriteLine("{0}% Done!", Interlocked.Increment(ref progress));
    });
});

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