VB.NET Math.Sqrt Description

You want to take the square root of a number in your VB.NET program. With the Math.Sqrt function, you pass one Double value as an argument, and receive the square root of that as another Double.

This VB article shows how to get square roots. It uses the Math.Sqrt Function.

Example

This program is very self-explanatory: it takes the square roots of four Doubles and prints them with Console.WriteLine. Notably, we can see that the square root of 1 is 1, and the square root of four is two.

Program that calls Math.Sqrt [VB.NET]

Module Module1
    Sub Main()
	Dim result1 As Double = Math.Sqrt(1)
	Dim result2 As Double = Math.Sqrt(2)
	Dim result3 As Double = Math.Sqrt(3)
	Dim result4 As Double = Math.Sqrt(4)

	Console.WriteLine(result1)
	Console.WriteLine(result2)
	Console.WriteLine(result3)
	Console.WriteLine(result4)
    End Sub
End Module

Output

1
1.4142135623731
1.73205080756888
2

Implementation

The Math.Sqrt function is not implemented in managed code. Rather, it calls into an unmanaged DLL. This means we cannot see its implementation in IL Disassembler.

Implementation of Sqrt [IL]

.method public hidebysig static float64 Sqrt(float64 d) cil managed internalcall
{
} // end of method Math::Sqrt

Performance

Let's look into the performance characteristics of Math.Sqrt. I was interested to see that some arguments to Math.Sqrt are much faster to pass than others. For example, Math.Sqrt(4) only takes two nanoseconds, while Math.Sqrt(4.1) takes six nanoseconds. The performance of Math.Sqrt largely depends on what arguments you pass to it.

Program that times Math.Sqrt [VB.NET]

Module Module1
	Sub Main()
	Dim m As Integer = 10000000
	Dim s1 As Stopwatch = Stopwatch.StartNew
	For i As Integer = 0 To m - 1
	    If Math.Sqrt(4) = 1 Then
		Throw New Exception
	    End If
	Next
	s1.Stop()

	Dim s2 As Stopwatch = Stopwatch.StartNew
	For i As Integer = 0 To m - 1
	    If Math.Sqrt(4.1) = 1 Then
		Throw New Exception
	    End If
	Next
	s2.Stop()

	Dim u As Integer = 1000000
	Console.WriteLine(((s1.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns"))
	Console.WriteLine(((s2.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns"))
    End Sub
End Module

Result

2.61 ns
6.20 ns

Summary

We examined several aspects of Math.Sqrt in the VB.NET programming language: how you can call it in a program; where it is implemented in the .NET Framework; and how fast it is. We were intrigued by how much the argument to the method affects the time it requires to compute its result.