[Solved] How to directly access objects in array with C# (without using unsafe)? [closed]

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Using an unsafe array in C# allows you to get direct pointers to the elements (if they are of intrinsic types). This should provide a performance benefit because there are no range checks to be done of each access. I know you said no unsafe code, but if you want performance you have to consider this option.

Consider the example below:

public unsafe class PinnedArray : IDisposable
{
    byte[] values;
    byte* pointer;
    GCHandle handle;

    public PinnedArray(int size)
    {
        values=new byte[size];
        handle=GCHandle.Alloc(values, GCHandleType.Pinned);
        pointer=(byte*)handle.AddrOfPinnedObject().ToPointer();
    }
    ~PinnedArray()
    {
        Dispose();
    }

    public void Dispose()
    {
        if(values!=null)
        {
            handle.Free();
            values=null;
        }
    }
    // This is fast because it uses pointers
    public void AddFrom(PinnedArray other)
    {
        if(values.Length!=other.values.Length)
        {
            throw new ArgumentException("other");
        }
        for(int i = 0; i<values.Length; i++)
        {
            pointer[i]+=other.pointer[i];
        }
    }        

    public void FillRandom()
    {
        Random rand = new Random();
        for(int i = 0; i<values.Length; i++)
        {
            values[i]=(byte)(rand.Next()%256);
        }
    }
}
class Program
{
    static void Main(string[] args)
    {
        var A = new PinnedArray(100);
        var B = new PinnedArray(100);

        B.FillRandom();
        A.AddFrom(B);
    }
}

With my testing I see a 20% speedup in doing math using pointers (pointer[i]) as opposed to array access (value[i]).

PS. This declaration comes from Microsoft. In their parallel toolkit examples there is a project named Strassens which benchmarks matrix multiplication and uses the above scheme for quick math.

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solved How to directly access objects in array with C# (without using unsafe)? [closed]