Discussion on: How to compare two files using .NET, really really fast!

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Be carefull the algorithm ReadFileInChunksAndCompareAvx2 is not correct you must move into oh1 and oh2 otherwise you are always comparing the same segment.

I would fix the last loop with :

var totalProcessed = 0;
while (totalProcessed < count1) {
    var result = Avx2.CompareEqual(Avx.LoadVector256(oh1+ totalProcessed), Avx.LoadVector256(oh2+totalProcessed));
    if (Avx2.MoveMask(result) != -1) {
        return false;
    }
    totalProcessed += Vector256<byte>.Count;
}