True Unsafe Code Performance

Question

I understand unsafe code is more appropriate to access things like the Windows API and do unsafe type castings than to write more performant code, but I would like to ask yo

Answer 1

As was stated in other posts, you can use unsafe code in very specialised contexts to get a significant performance inprovement. One of those scenarios is iterating over arrays of value types. Using unsafe pointer arithmetic is much faster than using the usual pattern of for-loop/indexer..

struct Foo
{
    int a = 1;
    int b = 2;
    int c = 0;
}

Foo[] fooArray = new Foo[100000];

fixed (Foo* foo = fooArray)  // foo now points to the first element in the array...
{
    var remaining = fooArray.length;
    while (remaining-- > 0)
    {
        foo->c = foo->a + foo->b;
        foo++;  // foo now points to the next element in the array...
    }
}

The main benefit here is that we've cut out array index checking entirely..

While very performant, this kind of code is hard to handle, can be quite dangerous (unsafe), and breaks some fundamental guidelines (mutable struct). But there are certainly scenarios where this is appropriate...