Is the size of an array constrained by the upper limit of int (2147483647)?

Question

I\'m doing some Project Euler exercises and I\'ve run into a scenario where I have want arrays which are larger than 2,147,483,647 (the upper limit of

Answer 1

According to MSDN, the index for array of bytes cannot be greater than 2147483591. For .NET prior to 4.5 it also was a memory limit for an array. In .NET 4.5 this maximum is the same, but for other types it can be up to 2146435071.

This is the code for illustration:

    static void Main(string[] args)
    {
        // -----------------------------------------------
        // Pre .NET 4.5 or gcAllowVeryLargeObjects unset
        const int twoGig = 2147483591; // magic number from .NET

        var type = typeof(int);          // type to use
        var size = Marshal.SizeOf(type); // type size
        var num = twoGig / size;         // max element count

        var arr20 = Array.CreateInstance(type, num);
        var arr21 = new byte[num];

        // -----------------------------------------------
        // .NET 4.5 with x64 and gcAllowVeryLargeObjects set
        var arr451 = new byte[2147483591];
        var arr452 = Array.CreateInstance(typeof(int), 2146435071);
        var arr453 = new byte[2146435071]; // another magic number

        return;
    }