How many reversible integer operations do you know?

Re:How many reversible integer operations do you know? by wilun on Sunday January 14, 2018 @11:36AM (#16144906)

> In other words, you'd need about 16GB just to store the program to compute the permutation!

Another way to reach this number is simply to consider that most reversible operations are going to be implementable by non-compressible LUTs, and such a LUT for 32-bits number will be 2^32 * 4 Bytes == 16GB.

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Re:How many reversible integer operations do you know? by Retric on Sunday January 14, 2018 @01:17PM (#16145417)

You can cut this in half because the inputs always map to different outputs and nothing repeats. So, after specifying the first mapping 0 > k, 1 can map to 2^32 -1 possible numbers, 2 can map to 2^32 - 2 numbers etc, and you can skip mapping the last number as only one possibility is left.

LUT's would be vastly faster though.

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