Cudos contest - 0xf15ers's results

1. Arrays length can be cached to save gas

• In Gravity.sol#L128, the array length can be cached like below

uint length = _users.length;
for (uint256 i = 0; i < _users.length; i++) {
  ............
}

Same for below:

./solidity/contracts/Gravity.sol:149:		 for (uint256 i = 0; i < _users.length; i++) {
./solidity/contracts/Gravity.sol:267:		for (uint256 i = 0; i < _currentValidators.length; i++) {
./solidity/contracts/Gravity.sol:299:		for (uint256 i = 0; i < _newValset.validators.length; i++) {
./solidity/contracts/Gravity.sol:489:				for (uint256 i = 0; i < _amounts.length; i++) {
./solidity/contracts/Gravity.sol:605:		for (uint256 i = 0; i < _args.transferAmounts.length; i++) {
./solidity/contracts/Gravity.sol:616:		for (uint256 i = 0; i < _args.feeAmounts.length; i++) {
./solidity/contracts/Gravity.sol:698:		for (uint256 i = 0; i < _powers.length; i++) {

2. Default initialisation can be omitted

• In Gravity.sol#L54, default value initialisation of 0 can be omitted.

uint256 public state_lastValsetNonce = 0

3. External function are cheaper than public functions

• Public functions not called anywhere inside the contract can be declared external to save gas.
• Function like manageWhitelist(), testCheckValidatorSignatures() updateValset() submitBatch() submitLogicCall() sendToCosmos(), etc. can be declared external.

4. Prefix increment is cheaper than postfix increment

• In Gravity.sol#L233, ++i can be used instead of i++ to save gas.

Same for below:

./solidity/contracts/Gravity.sol:150:		for (uint256 i = 0; i < _users.length; i++) {
./solidity/contracts/Gravity.sol:268:		for (uint256 i = 0; i < _currentValidators.length; i++) {
./solidity/contracts/Gravity.sol:300:		for (uint256 i = 0; i < _newValset.validators.length; i++) {
./solidity/contracts/Gravity.sol:490:				for (uint256 i = 0; i < _amounts.length; i++) {
./solidity/contracts/Gravity.sol:606:		for (uint256 i = 0; i < _args.transferAmounts.length; i++) {
./solidity/contracts/Gravity.sol:617:		for (uint256 i = 0; i < _args.feeAmounts.length; i++) {
./solidity/contracts/Gravity.sol:699:		for (uint256 i = 0; i < _powers.length; i++) {