Gas Optimizations

[code423n4]

1. Non-strict inequalities are cheaper than strict ones
   AuraLocker.sol#L724
   AuraVestedEscrow.sol#L158 (when _time = startTime, the final result will be 0 anyway)

2. Check require() at the beginning of function
   AuraBalRewardPool.sol#L77
   AuraLocker.sol#L385 (You can move this line to #L381 so that you can avoid unnecessary calculation for expiryTime)
   AuraMerkleDrop.sol#L69
   AuraMerkleDrop.sol#L152
   AuraPenaltyForwarder.sol#L51-L52 (You can move these lines to #L49)
   AuraVestedEscrow.sol#L63-L66 (You can move these lines to #L58)

3. Declare memory variable instead of calling locks[i] several times
   AuraLocker.sol#L696-L707

4. Change storage to memory if possible
   AuraLocker.sol#L172
   AuraLocker.sol#L377
   AuraLocker.sol#L469
   AuraLocker.sol#L659
   AuraLocker.sol#L692
   AuraLocker.sol#L693
   Booster.sol#L399
   Booster.sol#L454
   Booster.sol#L573
   ConvexMasterChef.sol#L157
   ConvexMasterChef.sol#L158
   ConvexMasterChef.sol#L263

5. Don't use storage value if possible
   AuraVestedEscrow.sol#L65 (You can use starttime_, endtime_ instead of startTime, endTime)

6. Use != 0 instead of > 0 for uint variables
   There are more than 30 cases and I will show just one example.
   I think you can change them easily if you want.
   Aura.sol#L68

7. Use ++i instead of i++, i+=1 (also for --i)
   There are more than 30 cases and I will show just one example.
   Also you can use "unchecked" for such increments.
   AuraClaimZap.sol#L143

8. No need to initialize variables with default values
   There are more than 30 cases and I will show just one example for uint and all for bool.
   AuraBalRewardPool.sol#L35
   AuraLocker.sol#L114
   AuraVestedEscrow.sol#L33

9. An array’s length should be cached to save gas in for-loops
   AuraClaimZap.sol#L143
   AuraClaimZap.sol#L147
   AuraClaimZap.sol#L151
   AuraLocker.sol#L696
   AuraLocker.sol#L699
   AuraVestedEscrow.sol#L100
   ArbitartorVault.sol#L49
   BaseRewardPool.sol#L214
   BaseRewardPool.sol#L230
   BaseRewardPool.sol#L262
   BaseRewardPool.sol#L296
   Booster.sol#L379
   Booster.sol#L538
   PoolManagerSecondaryProxy.sol#L69

10. Use if(flag) instead of if(flag == true) [use if(!flag) instead of if(flag == false)]
    RewardFactory.sol#L72
    VoterProxy.sol#L107
    VoterProxy.sol#L168
    VoterProxy.sol#L171
    VoterProxy.sol#L190
    AuraMerkleDrop.sol#L123
    Booster.sol#L400
    Booster.sol#L574