Rigor Protocol contest - gerdusx's results

Gas Optimizations

[G-01] Use prefix not postfix in loops

Using a prefix increment (++i) instead of a postfix increment (i++) saves gas for each loop cycle and so can have a big gas impact when the loop executes on a large number of elements.

There are 11 occurrences

• for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 _taskID = 1; _taskID <= _length; _taskID++) {
• for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {
• for (; i < _changeOrderedTask.length; i++) {
• for (++j; j <= taskCount; j++) {
• for (uint256 _taskID = 1; _taskID <= _length; _taskID++) {

Recommended Mitigation Steps

Use prefix, not postfix to increment in a loop

[G-02] Redundant zero initialization

Solidity does not recognize null as a value, so uint variables are initialized to zero. Setting a uint variable to zero is redundant and can waste gas.

There are 7 occurrences

• for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {

Recommended Mitigation Steps

Remove the redundant zero initialization

uint256 amount;

[G-03] Use != 0 instead of > 0

Using > 0 uses slightly more gas than using != 0. Use != 0 when comparing uint variables to zero, which cannot hold values below zero.

There are 10 occurrences

• return projectTokenId[_project] > 0;
• require(_cost > 0, "Project::!value>0");
• if (_leftOutTokens > 0) {
• if (_changeOrderedTask.length > 0) {
• _actionType > 0 && _actionType <= uint8(ActionType.TaskPay),
• if (projectPublished[_project] > 0) {
• _communities[_communityID].projectDetails[_project].lentAmount > 0
• if (_loopCount > 0) emit TaskAllocated(_tasksAllocated);
• require(_repayAmount > 0, "Community::!repay");
• if (_interestEarned > 0) {

Recommended Mitigation Steps

Replace > 0 with != 0 to save gas

[G-04] Adding unchecked directives can save gas

For the arithmetic operations that will never over/underflow, using the unchecked directive (Solidity v0.8 has default overflow/underflow checks) can save some gas from the unnecessary internal over/underflow checks.

There are 11 occurrences

• for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 i = 0; i < _length; i++) {
• for (uint256 _taskID = 1; _taskID <= _length; _taskID++) {
• for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {
• for (; i < _changeOrderedTask.length; i++) {
• for (++j; j <= taskCount; j++) {
• for (uint256 _taskID = 1; _taskID <= _length; _taskID++) {

Recommended Mitigation Steps

Consider applying unchecked arithmetic where overflow/underflow is not possible. An example can be seen below.

    for (uint256 i; i < length;) {
        // ...
        unchecked { ++i };
    }