├── test.sol
└── README.md


/test.sol:
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 1 | pragma solidity 0.8.15;
 2 | 
 3 | contract Test {
 4 | 
 5 |     // 5 loops, total gas cost == 22138
 6 |     // 100 loops, total gas cost == 27743
 7 |     // 1000 loops, total gas cost == 80855
 8 |     function increment0(uint256 loops) external pure returns (uint256) {
 9 |         uint256 value;
10 |         for (uint256 i; i < loops;) {
11 |             unchecked { ++i; }
12 |             value = i;
13 |         }
14 |         return value;
15 |     }
16 | 
17 |     // 5 loops, total gas cost == 22051
18 |     // 100 loops, total gas cost == 26326
19 |     // 1000 loops, total gas cost == 66838
20 |     function increment1(uint256 loops) external pure returns (uint256) {
21 |         uint256 value;
22 |         for (uint256 i;;) {
23 |             unchecked { ++i; }
24 |             value = i;
25 |             if (i >= loops) break;
26 |         }
27 |         return value;
28 |     }
29 | 
30 |     // 5 loops, total gas cost == 22019
31 |     // 100 loops, total gas cost == 26294
32 |     // 1000 loops, total gas cost == 66806
33 |     function increment2(uint256 loops) external pure returns (uint256) {
34 |         uint256 value;
35 |         for (uint256 i;;) {
36 |             unchecked { i += 1; } // i += 1 cheaper than ++i
37 |             value = i;
38 |             if (i >= loops) break;
39 |         }
40 |         return value;
41 |     }
42 | 
43 | }


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/README.md:
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 1 | # More optimal for loops
 2 | 
 3 | In test.sol there are 3 functions with the total gas cost in comments above them:
 4 | 
 5 | - **increment0** : The unchecked style for loop 
 6 | 
 7 | - **increment1** : A cheaper more optimized version of increment0
 8 | 
 9 | ## Total gas cost breakdown
10 | ### increment0
11 | | loop count | gas cost |
12 | |------------|----------|
13 | | 5    | 22138 |
14 | | 100  | 27743 |
15 | | 1000 | 80855 |
16 | 
17 | ### increment1
18 | | loop count | gas cost |
19 | |------------|----------|
20 | | 5    | 22051 |
21 | | 100  | 26326 |
22 | | 1000 | 66838 |
23 | 
24 | ### increment2
25 | | loop count | gas cost |
26 | |------------|----------|
27 | | 5    | 22019 |
28 | | 100  | 26294 |
29 | | 1000 | 66806 |
30 | 
31 | 
32 | 
33 | 
34 | 
35 | ## OPCODES
36 | 
37 | 
38 | ### increment0
39 | ### 58 total gas per loop
40 | ##### OPCODES for 1 loop with increment0
41 | 
42 | 
43 | 
44 | | OPCODE        | GAS                                                    |
45 | |---------------|--------------------------------------------------------|
46 | | JUMPDEST	| 1 gas, one time cost. wont count this in total.        |
47 | | DUP4. 	| 3 gas							 |
48 | | DUP2	        | 3 gas							 |
49 | | LT		| 3 gas							 |
50 | | ISZERO	| 3 gas							 |
51 | | PUSH2 0112	| 3 gas							 |
52 | | JUMPI		| 10 gas						 |
53 | | DUP1		| 3 gas							 |
54 | | PUSH1 01	| 3 gas							 |
55 | | ADD		| 3 gas							 |
56 | | SWAP1		| 3 gas							 |
57 | | POP		| 2 gas							 |
58 | | DUP1		| 3 gas							 |
59 | | SWAP2		| 3 gas							 |
60 | | POP		| 2 gas							 |
61 | | PUSH2 00fc	| 3 gas							 |
62 | | JUMP		| 8 gas							 | 
63 | 
64 | 
65 | ### increment1
66 | ### 47 gas total per loop
67 | #### OPCODES for 1 loop with increment1
68 | 
69 | 
70 | | OPCODE	| GAS							|
71 | |---------------|-------------------------------------------------------|
72 | | JUMPDEST   	| 1 gas, one time on cost. wont count this in total	|
73 | | DUP1		| 3 gas							|
74 | | PUSH1 01	| 3 gas							|
75 | | ADD		| 3 gas							|
76 | | SWAP1		| 3 gas							|
77 | | POP		| 2 gas							|
78 | | DUP1		| 3 gas							|
79 | | SWAP2		| 3 gas							|
80 | | POP		| 2 gas							|
81 | | DUP4		| 3 gas							|
82 | | DUP2		| 3 gas							|
83 | | GT		| 3 gas							|
84 | | ISZERO	| 3 gas							|
85 | | PUSH2 0122    | 3 gas							|
86 | | JUMPI		| 10 gas						|
87 | 
88 | 
89 | ## EXPLANATION
90 |   So when we declare our loop break condition in the for loop, we have check at the beginning of every loop, followed by a JUMPI which is a conditional jump that basically says if this is false jump out of the loop but if its true jump into the loop. And if its true we continue through the loop and then hit the end and have to hit an additonal jump to get back to the top of the loop.
91 |   But in the new way we just continue through the loop and hit our condition at the end and then hit only one JUMPI which says either jump back to the top of the loop or just jump out of the loop. All in all saving us 11 gas a loop, plus possibly some additional gas on the for loop setup
92 |   
93 |   Now for this to work your if statement with the loop break has to be the very last thing in your loop. You have to increment i then check the conditional
94 | 


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