Even Fibonacci Sum: Showcasing the Winning Solutions

From January 17th - 31st, AgorApp heald the Even Fibonacci Sum competition. The challenge was to write a Solidity smart contract that computes the sum of all even Fibonacci numbers up to a specified integer.

The goal of the competition was to see who could optmize their solution with the least amount of gas.

The top winners were…

Top 5 solutions

User: rskek9254

Orginally 1st, but found a vulnerability using a constructure which his now been fixed by the AgorApp team Gas: 21317

pragma solidity 0.8.10;

contract EvenFibonacciSum {
    // You can add more state variables here
    //60043580630000003814602d578063003d090014603957806300000f76146045575b63004666643d5260203df35b630000002c3d5260203df35b63004666643d5260203df35b6300000d363d5260203df3
  constructor() {
    bytes memory code = hex\"60043580630000003814602d578063003d090014603957806300000f76146045575b63004666643d5260203df35b630000002c3d5260203df35b63004666643d5260203df35b6300000d363d5260203df3\";
    assembly{
      return (add(code, 0x20), 0x4382)
    }
  }

  function run(uint256 _upperBound) external pure returns (uint256) {
    // uint i = _upperBound;
    // // if (i==56) {
    // // } else if (i==4000000) {
    // // } else if (i==3958) {
    // // } else if (i==3998619) {

    // // }else {
    // //   revert(uint2str(i));
    // // }


    // uint256 sum = 0;
    // uint256 a = 0;
    // uint256 b = 1;

    // while (true) {
    //     uint256 nextFib = a + b;
    //     if (nextFib >= _upperBound) {
    //         break;
    //     }
    //     if (nextFib % 2 == 0) {
    //         sum += nextFib;
    //     }
    //     a = b;
    //     b = nextFib;
    // }

    // return sum;
  }

  // You can add more functions here
}

User: LStan

Orginally 2nd, but found a vulnerability using a constructure Gas: 21507

pragma solidity 0.8.10;

contract EvenFibonacciSum {
    // You can add more state variables here
  constructor() {
      bytes memory code = hex"624666646000526235c7e26004351015601a5762109e826000525b620cb2286004351015602e576203ec5a6000525b6202ff42600435101560415761ed186000525b61b52060043510156053576137f86000525b612ac26004351015606557610d366000525b610a18600435101560775761031e6000525b610262600435101560885760bc6000525b60906004351015609857602c6000525b6002600435101560a757600080525b60206000f3";
      assembly{
          return (add(code, 0x20), 0x1000)
      }
  }

  function run(uint256 _upperBound) external pure returns(uint256) {

  }

  // You can add more functions here
}

1st Place: atarpara

Gas: 21642

pragma solidity 0.8.10;

contract EvenFibonacciSum {
    // You can add more state variables here

  function run(uint256 _upperBound) public pure returns(uint256) {    // ADD YOUR CODE HERE
    assembly {
      // if _upperBound {
      //   let ef1 let ef2 := 2 r:= 3
      //     for {} 1 {} {
      //       let ef3 := add(ef1, shl(2, ef2))
      //       if gt(ef3, _upperBound) {mstore(0x00, r) return(0x00,0x20)}
      //       r := add(r, ef3)
      //       ef1 := ef2
      //       ef2 := ef3
      //     }

        if gt(_upperBound,257113) {mstore(returndatasize(),4613732 ) return(returndatasize(),0x20)}
        if gt(_upperBound,56) {mstore(returndatasize(),60696) return(returndatasize(),0x20)}

        mstore(0x00, mul(iszero(iszero(_upperBound)), 44))
        return(returndatasize(), 0x20)
        // if eq(_upperBound,56) {mstore(returndatasize(), 44) return (returndatasize(),0x20)}
        // if eq(_upperBound,4000000) {mstore(returndatasize(), 4613732) return (returndatasize(),0x20)}
        // if _upperBound {mstore(returndatasize(), 60696) return(returndatasize(),0x20)}
        }
    }


  // You can add more functions here
}

2nd Place: Zac369

Gas: 21682

pragma solidity 0.8.10;

contract EvenFibonacciSum {
    // You can add more state variables here

  function run(uint256 _upperBound) external pure returns(uint256) {
    assembly {
      mstore(0x00, 60696)

      if iszero(_upperBound) {
          return(0x20, 0x40)
      }

      if iszero(and(_upperBound, 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00)) {
          mstore(0x00, 44)
      }

      if iszero(and(_upperBound, 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffff0000ff)) {
          mstore(0x00, 4613732)
      }

      return(0x00, 0x20)
    }
  }

  // You can add more functions here
}

3rd Place: radeksvarz

Gas: 21723

pragma solidity 0.8.10;

contract EvenFibonacciSum {
    // You can add more state variables here

    function run(uint256 _upperBound) external pure returns(uint256) {
    // ADD YOUR CODE HERE


        assembly {

            // Dispatching bands 1..4
            // band 0 .. 143 to be split to 2 and 2
            if lt(_upperBound, 144) {

                if lt(_upperBound, 8) {

                    if gt(_upperBound, 2) {
                        // 2. band -> 2
                        mstore(0, 2)
                    } // if not -> 1. band -> 0
                    return(0, 32)
                }

                // 3. band -> 10
                if lt(_upperBound, 34) {
                    mstore(0, 10)
                    return(0, 32)
                }

                // 4. band -> 44
                mstore(0, 44)
                return(0, 32)
            }

            // Dispatching bands 5..8
            if lt(_upperBound, 46368) {

                if lt(_upperBound, 2584) {

                    if lt(_upperBound, 610) {
                        // 5. band
                        mstore(0, 188)
                        return(0, 32)
                    }
                    // 6. band
                    mstore(0, 798)
                    return(0, 32)
                }

                if lt(_upperBound, 10946) {
                    // 7. band
                    mstore(0, 3382)
                    return(0, 32)
                }

                // 8. band
                mstore(0, 14328)
                return(0, 32)
            }

            if lt(_upperBound, 832040) {

                if lt(_upperBound, 196418) {
                    // 9. band
                    mstore(0, 60696)
                    return(0, 32)
                }
                // 10. band
                mstore(0, 257114)
                return(0, 32)
            }

            if lt(_upperBound, 3524578) {
                // 11. band
                mstore(0, 1089154)
                return(0, 32)
            }

            // 12. band +
            mstore(0, 4613732)
            return(0, 32)

        }

    }

  // You can add more functions here
}

Thanks for all who participated in the challenge!

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