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There are a bewildering array (excuse the pun) of data storage structures available to you in Visual Basic. Choose from arrays, ArrayLists, SortedLists, Dictionaries, HashTables, Lists and DataTables, among others. This blog gives an example of each type of structure, and benchmarks them to show which perform best and worst.
- VB.NET Data Storage Types Compared and Benchmarked
- VB.NET Benchmarking Test of speeds of data structures
- Arrays - Visual Basic data structures (this blog)
- ArrayLists and SortedLists - Visual Basic data structures
- Dictionaries and HashTables - Visual Basic data structures
- Lists - Visual Basic data structures
- Using data tables - Visual Basic data structures
- Benchmark Results and Recommendations
Posted by Andy Brown on 24 August 2011
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Arrays
An array holds related data in numbered cells. Thus an array of 3 friends' names might read:
- Friends(0) = "Shadrach"
- Friends(1) = "Meshach"
- Friends(2) = "Abednego"
Arrays are always numbered from 0 in .NET.
In addition, you can have static and dynamic arrays:
| Type of array | Notes |
|---|---|
| Static | In a static array, you specify the size of the array when you first create it, and it doesn't subsequently increase. |
| Dynamic | In a dynamic array, whenever you find a new value you increase the size of the array by 1 to accommodate it. |
Here is the code I used to test the static array. I've given it a fixed size of 100,000 elements, so it can accommodate lots of data.
Sub ArrayStatic()
Dim test(99999) As String
StartTimer()
'read values into static array
Dim i As Integer
For i = 0 To (10 ^ RunSize) - 1
test(i) = TestCode(i)
Next
'work out how long this took
WriteTime = ElapsedTime
'store ten values for subsequent tests
StoreTenValues()
'sort the array (timing this)
Array.Sort(test)
SortTime = ElapsedTime
'third test: find 10 "random" values by number
Dim s As String
For i = (10 ^ RunSize) - 1 To 0 Step -(10 ^ (RunSize - 1))
s = test(i)
Next
'report how long this took
Read1Time = ElapsedTime
'fourth test: find 10 "random" values by name
For i = 0 To 9
s = TextValues(i)
For j = 0 To (10 ^ RunSize) - 1
If test(j) = s Then
Exit For
End If
Next
Next
'this shows results on my internal site
AddRow("Array", "Static array (fixed size 10000)")
End Sub
The code to test a dynamic array is as follows:
Sub ArrayDynamic()
Dim test() As String = Nothing
StartTimer()
'first test: writing 10 ^ n values, increasing size of the array by 1 each time
'(note the word PRESERVE to avoid losing previous contents)
Dim i As Integer
For i = 0 To (10 ^ RunSize) - 1
ReDim Preserve test(i)
test(i) = TestCode(i)
Next
'work out how long this took
WriteTime = ElapsedTime
'store ten values for subsequent tests
StoreTenValues()
'sort the array (timing this)
Array.Sort(test)
SortTime = ElapsedTime
'third test: find 10 "random" values by number
Dim s As String
For i = (10 ^ RunSize) - 1 To 0 Step -(10 ^ (RunSize - 1))
s = test(i)
Next
'report how long this took
Read1Time = ElapsedTime
'fourth test: find 10 "random" values by name
For i = 0 To 9
s = TextValues(i)
For j = 0 To (10 ^ RunSize) - 1
If test(j) = s Then
Exit For
End If
Next
Next
Read2Time = ElapsedTime
'write out results of test
AddRow("Array", "Dynamic array")
End Sub
The results of running these tests are shown at the end of this blog.
- VB.NET Data Storage Types Compared and Benchmarked
- VB.NET Benchmarking Test of speeds of data structures
- Arrays - Visual Basic data structures (this blog)
- ArrayLists and SortedLists - Visual Basic data structures
- Dictionaries and HashTables - Visual Basic data structures
- Lists - Visual Basic data structures
- Using data tables - Visual Basic data structures
- Benchmark Results and Recommendations