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Experimental power number generator for uints #892

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merged 9 commits into from
Apr 11, 2023
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@ggrieco-tob ggrieco-tob commented Jan 5, 2023

This should be considered experimental until we know it works better

@rappie
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rappie commented Jan 6, 2023

I have run some tests. It does not seem to be working.

I would expect echidna to be able to break testAmount without the helper. It needs a number between 1e16 and 1e20, which should occur frequently now in the distribution of the random numbers.

pragma solidity ^0.8.0;

contract EchidnaTest {
    uint256 private constant min = 16;
    uint256 private constant max = 20;

    function helper(uint256 amount) public {
        amount = (10**min) + (amount % ((10**max) - (10**min)));
        testAmount(amount);
    }

    function testAmount(uint256 amount) public {
        if (amount > (10**min) && amount < (10**max)) {
            assert(false);
        }
    }
}
testMode: assertion
testLimit: 100000

@ggrieco-tob
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This is working now, thanks @rappie !

@ggrieco-tob ggrieco-tob marked this pull request as ready for review January 6, 2023 21:25
@rappie
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rappie commented Jan 31, 2023

I have tested this.

As expected, it is noticably slower to break certain properties than before, but it does manage to break them without helpers.

Personally I'd prefer to have only the logarithmic RNG. I believe this to be superior for fuzzing, but then again I'm no expert :)

[ (getRandomR (0, 1023), 1)
, (getRandomR (0, 2 ^ n - 5), 8)
, (getRandomR (2 ^ n - 5, 2 ^ n - 1), 1)
, (getRandomPow (n - 5), 4)
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as I understand the chance of this happening will be 4/14 ~ 28%?

@ggrieco-tob ggrieco-tob merged commit 558baef into master Apr 11, 2023
@ggrieco-tob ggrieco-tob deleted the dev-power-gen branch April 11, 2023 17:37
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3 participants