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QuickStart Samples

Basic Vectors QuickStart Sample (Visual Basic)

Illustrates the basic use of the Vector class for working with vectors in Visual Basic.

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Option Infer On

' The Vector class resides in the Extreme.Mathematics.LinearAlgebra namespace.
Imports Extreme.Mathematics
Imports Extreme.Mathematics.LinearAlgebra

Namespace Extreme.Numerics.QuickStart.VB
    ' Illustrates the use of the Vector class in the 
    ' Extreme.Mathematics.LinearAlgebra namespace of the Extreme Optimization
    ' Numerical Libraries for .NET.
    Module BasicVectors

        Sub Main()
            '
            ' Constructing vectors
            '

            ' Option #1: specify the number of elements. All
            ' elements are set to 0.
            Dim v1 = Vector.Create(Of Double)(5)
            ' Option #2: specify the elements:
            Dim v2 = Vector.Create(New Double() {1, 2, 3, 4, 5})
            ' Option #3: specify the elements as a Double array.
            ' By default, the elements are copied to a storage
            ' area internal to the Vector.
            Dim elements As Double() =
                New Double() {1, 2, 3, 4, 5}
            Dim v3 = Vector.Create(elements)
            ' Option #4: same as above, but specify whether
            ' to copy the elements, or reuse the array as 
            ' internal storage.
            Dim v4 = Vector.Create(elements, True)
            ' Changing a value in the original vector changes
            ' the resulting vector.
            Console.WriteLine("v4 = {0:F4}", v4)
            elements(3) = 1
            Console.WriteLine("v4 = {0:F4}", v4)
            ' Option #5: same as #4, but specify the length of
            ' the Vector. The remaining elements in the element
            ' array will be ignored.
            Dim v5 = Vector.Create(4, elements, True, ArrayMutability.Immutable)

            '
            ' Vector properties
            '

            ' The Length property gives the number of elements
            ' of a Vector:
            Console.WriteLine("v1.Length = {0}", v1.Length)
            ' The ToArray() method returns a Double array
            ' that contains the elements of the vector.
            ' This is always a copy:
            elements = v2.ToArray()
            Console.WriteLine("Effect of shared storage:")
            Console.WriteLine("v2(2) = {0}", v2(2))
            elements(2) = 1
            Console.WriteLine("v2(2) = {0}", v2(2))

            '
            ' Accessing vector elements
            '

            ' The Vector class defines an indexer property that
            ' takes a zero-based index.
            Console.WriteLine("Assigning with private storage:")
            Console.WriteLine("v1(2) = {0}", v1(2))
            ' You can assign to this property:
            v1(2) = 7
            Console.WriteLine("v1(2) = {0}", v1(2))
            ' The vectors v4 and v5 had the reuse parameter in the
            ' constructor set to true. As a result, they share 
            ' their element storage. Changing one vector also 
            ' changes the other:
            Console.WriteLine("Assigning with shared storage:")
            Console.WriteLine("v5(1) = {0}", v5(1))
            v5(1) = 7
            Console.WriteLine("v5(1) = {0}", v5(1))

            ' The SetValue method sets all elements of a vector
            ' to the same value:
            v1.SetValue(1)
            Console.WriteLine("v1 = {0:F4}", v1)
            ' The Zero method sets all elements to 0:
            v1.SetToZero()
            Console.WriteLine("v1 = {0:F4}", v1)

            '
            ' Copying and cloning vectors
            '

            ' A shallow copy of a vector constructs a vector
            ' that shares the element storage with the original.
            ' This is done using the ShallowCopy method:
            Console.WriteLine("Shallow copy vs. clone:")
            Dim v7 = v2.ShallowCopy()
            ' The clone method creates a full copy.
            Dim v8 = v2.Clone()
            ' When we change v2, v7 changes, but v8 is left
            ' unchanged.
            Console.WriteLine("v2(1) = {0}", v2(1))
            v2(1) = -2
            Console.WriteLine("v7(1) = {0}", v7(1))
            Console.WriteLine("v8(1) = {0}", v8(1))
            ' We can give a vector its own element storage
            ' by calling the CloneData method:
            Console.WriteLine("CloneData:")
            v7.CloneData()
            ' Now, changing the original v2 no longer changes v7:
            v2(1) = 4
            Console.WriteLine("v7(1) = {0}", v7(1))
            ' The CopyTo method copies the elements of a Vector
            ' to a variety of destinations. It may be a Vector:
            Console.WriteLine("CopyTo:")
            v5.CopyTo(v1)
            Console.WriteLine("v6 = {0:F4}", v5)
            Console.WriteLine("v1 = {0:F4}", v1)
            ' You can specify an index where to start copying
            ' in the destination vector:
            v5.CopyTo(v1, 1)
            Console.WriteLine("v1 = {0:F4}", v1)
            ' Or you can copy to a Double array:
            v5.CopyTo(elements)

            Console.Write("Press Enter key to exit...")
            Console.ReadLine()
        End Sub

    End Module

End Namespace