Question

public static void Main()
{
    int size = 250000;
    var a = new int[size];
    for (int i = 0; i < size; i++)
        Console.WriteLine("{0}", a[i]);
}

When I tested the above code with CLRProfiler, it told me that the code allocates roughly 40 MB. Around 20 MB is allocated to String, 9 MB to Char[], 5 MB to StringBuilder and 3 MB to Int32.

public static void Main()
{
    int size = 250000;
    var a = new int[size];
    for (int i = 0; i < size; i++)
        Console.WriteLine("0");
} 

This one allocates around 5 MB. 4 MB is allocated to Char[].

The only thing I get is that array a should require 1 MB (250,000 * 4).

Why is there such a massive difference ? Why are all those objects required for the first code and how do I reduce the memory allocation ?

Answer 1

Most likely the memory increase is because of the complexity involved in parsing the format string.

In your first case, it has to parse the format string, get a localized string representing the integer and put it in the right place of the format string.

In your second case you are outputting just a single value, and even more so, a plain string. It is very trivial in comparison.

If you are interested in what goes on under the covers you can use .NET Reflector and have a look at the WriteLine overloads.