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You state that a Feistel network has the property that each input value is mapped to a different output value, but how do you ensure that there isn't some cycle
by Orangeair 9y ago
You state that a Feistel network has the property that each input value is mapped to a different output value, but how do you ensure that there isn't some cycle whose length is shorter than that of the size of the set of possible inputs? That is to say, what guarantees that every pixel is reached at least once?
- antirez 9y agoHello, please check the chillingeffect comment replies, it is basically the same question. There are no cycles since it's not a generator where the previous number is the seed for the next. It's a transformation which is invertible and guaranteed to be unique by the Feistel network structure itself.
- first_amendment 9y agoFeistel is a permutation. That means it's a 1:1 mapping between a 16-bit # to another 16-bit #. You run Feistel for each number 0->65535 (corresponding to the "stage" of the FizzleFade) and out comes the pixel to redden at that stage. Since it's a 16-bit number, some values will fall outside of 320x240 resolution, and you ignore those.
- antirez 9y agoGreat TLDR!