Fastest method to check if an array is empty

Question

I want to know the fastest way to check if an array is empty in VB.NET. The array is already initialized so I can't use any of the checks that look at that. This is the current code below:

If Not (cubes(threadnumber)(i).objects.GetLength(0) = 0) Then
   cubes(threadnumber)(i).objects = New Double() {}
   ReDim cubes(threadnumber)(i).objects(-1)
End If

I've done some testing and I know that using .GetUpperBound is a little faster, but I'm not sure if this will work because I think .GetUpperBound returns a 0 if the array length is 1.

Any/all methods to speed this up (even fractionally) will be tremendously helpful. This program takes ages to compleate and the first line of the above code is a big portion of the time, it's called 136 million times.

Also if anyone knows how to speed up For...Next loops that'd be great too!

Answer 1

Length is about 2x faster than GetLength on my system (calling Length 136M times takes 0.650 seconds, while calling GetLength (0) takes 1.480 seconds).

I also do not understand why you ReDim your array, you've already created a new one.

I believe this will be the fastest code if cubes is a multi-dimensional array:

If cubes(threadnumber)(i).objects.Length > 0 Then
    cubes(threadnumber)(i).objects = New Double() {}
End If

If cubes is not a multi-dimensional array (like List for instance), you should take the cubes(threadnumber) code out of the loop.

Update

Length is 6x faster than GetLength when running in Release mode without the debugger, in which case Length takes 0.181s and GetLength 1.175s on my system. This is likely because the JIT will inline the call to Length, but not the call to GetLength.

This is the test code I used.

Answer 2

if myarray is nothing then...

or

if myarray isnot nothing then...