Given two arrays, how can I tell if a math result would overflow?

Question

In this case, sum is an int and I am intentionally setting one[] and [two] to int.MaxValue.

The result for sum is 1.

How can I tell if the result of a math function is going to overflow here, prior to attempting it?

sum += one[i] * two[i];

This might help you https://stackoverflow.com/questions/1657834/how-can-i-check-if-multiplying-two-numbers-in-java-will-cause-an-overflow — MA1, Jan 28 '18 at 19:36
What if your maths get more complicated, e.g. `Math.Pow(1231221, 2322)`? It´s impossible to know *before* you execute it and see what happens. — MakePeaceGreatAgain, Jan 28 '18 at 19:48
@HimBromBeere that is true for any function you call. but I think, question is about basic ops CPU can handle. — L.B, Jan 28 '18 at 20:24
I did this using the C# `checked()` keyword, which forces it to throw. It's the only way I can catch it and handle it. I don't see any way around it. — Patrick, Jan 28 '18 at 20:29

score 0 · Accepted Answer · edited Jan 28 '18 at 19:45

By 'overflow', did you mean it will exceed int.MaxValue? If so, try to use checked block. As @AlexD mentioned in comments, it won't perform a prior-check; however, it will raise an exception in case of overflow.

Quote and code sample are taken from MSDN:

The checked keyword is used to explicitly enable overflow checking for integral-type arithmetic operations and conversions.

// If the previous sum is attempted in a checked environment, an 
// OverflowException error is raised.

// Checked expression.
Console.WriteLine(checked(2147483647 + ten));

// Checked block.
checked
{
    int i3 = 2147483647 + ten;
    Console.WriteLine(i3);
}

Given two arrays, how can I tell if a math result would overflow?

1 Answers1