AbraNFT contest - Tadashi's results

Constants not used

Details: constant USE_VALUE2 (L566 of NFTPair.sol and L599 of NFTPairWithOracle.sol) is not used. It can be removed to save gas during deployment.

Change usage of ≥ for >

Details: EVM instruction set does not have an opcode for less than or equal, so L494 of NFTPair.sol can be changed to for (uint256 k = 1; k < COMPOUND_INTEREST_TERMS; k++) { to optimize gas costs.

Mutatis mutandis, the same applies to L527 of NFTPairWithOracle.sol.

Remark: also note that k++ can be changed to ++k to economize even more execution gas.

Split require to avoid using && opcode

Details: Apply the following changes to avoid using && and improve gas usage:

• Change L622 from NFTPair.sol and L655 from NFTPairWithOracle.sol to:

  require(callee != address(bentoBox), "NFTPair: can't call");
  require(callee != address(collateral), "NFTPair: can't call");
  require(callee != address(this), "NFTPair: can't call");

• Change L188-191 from NFTPair.sol to

  require(params.duration >= cur.duration, "NFTPair: worse params");
  require(params.valuation <= cur.valuation, "NFTPair: worse params");
  require(params.annualInterestBPS <= cur.annualInterestBPS, "NFTPair: worse params");

• Change L205-211 from NFTPairWithOracle.sol to

  require(params.duration >= cur.duration, "NFTPair: worse params");
  require(params.valuation <= cur.valuation, "NFTPair: worse params");
  require(params.annualInterestBPS <= cur.annualInterestBPS, "NFTPair: worse params");
  require(params.ltvBPS <= cur.ltvBPS, "NFTPair: worse params");

• Change L283-288 from NFTPair.sol to

  require(params.valuation == accepted.valuation, "NFTPair: bad params");
  require(params.duration <= accepted.duration, "NFTPair: bad params");
  require(params.annualInterestBPS >= accepted.annualInterestBPS, "NFTPair: bad params");

• Change L312-318 from NFTPairWithOracle.sol to

  require(params.valuation == accepted.valuation, "NFTPair: bad params");
  require(params.duration <= accepted.duration, "NFTPair: bad params");
  require(params.annualInterestBPS >= accepted.annualInterestBPS, "NFTPair: bad params");
  require(params.ltvBPS >= accepted.ltvBPS, "NFTPair: bad params");

Remark: I only recommend these optimizations if AbraNFT gives proper documentation for the errors NFTPair: can't call , NFTPair: worse params, and NFTPair: bad params. Otherwise, developers may miss one of the conditions when debugging a reverted transaction.

Pre-incrementing a variable is cheaper than post-incrementing it.

Details:

• i++ can be replaced by ++i in the loop of L641 of NFTPair.sol
• i++ can be replaced by ++i in the loop of L674 of NFTPairWithOracle.sol
• k++ can be replaced by ++k in the loop of L494 of NFTPair.sol
• k++ can be replaced by ++k in the loop of L527 of NFTPairWithOracle.sol