This repo illustrates the difference in gas costs when using a Uint256 and a felt based token on StarkNet.
It contains two ERC20 implementations:
- the
uintone is a copy of OpenZeppelin's ERC20, v0.3.1 - the
afeltone is based on the OZ token with a slight modification of completely dropping the use ofUint256and replacing if withfelts everywhere
I used the standard testing framework to gather the transaction execution resources. The cost calculation is using v.0.8.0 fees and does not take into account storage costs as those would be the same (assuming values less than 2^128).
Here is the breakdown:
# pytest -s tests/uint/test_ERC20.py::test_approve
tests/uint/test_ERC20.py Uint256 test_approve
ExecutionResources(n_steps=501, builtin_instance_counter={'pedersen_builtin': 2, 'range_check_builtin': 10, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=17)
Gas cost: 55.45
# pytest -s tests/afelt/test_ERC20.py::test_approve
tests/afelt/test_ERC20.py felt test_approve
ExecutionResources(n_steps=470, builtin_instance_counter={'pedersen_builtin': 2, 'range_check_builtin': 6, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=16)
Gas cost: 52.3# pytest -s tests/uint/test_ERC20.py::test_transfer
tests/uint/test_ERC20.py Uint256 test_transfer
ExecutionResources(n_steps=889, builtin_instance_counter={'pedersen_builtin': 4, 'range_check_builtin': 32, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=46)
Gas cost: 84.45000000000002
# pytest -s tests/afelt/test_ERC20.py::test_transfer
tests/afelt/test_ERC20.py felt test_transfer
ExecutionResources(n_steps=673, builtin_instance_counter={'pedersen_builtin': 4, 'range_check_builtin': 17, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=80)
Gas cost: 67.65# pytest -s tests/uint/test_ERC20.py::test_transferFrom
tests/uint/test_ERC20.py Uint256 test_transferFrom
ExecutionResources(n_steps=1305, builtin_instance_counter={'pedersen_builtin': 8, 'range_check_builtin': 51, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=67)
Gas cost: 114.45
# pytest -s tests/afelt/test_ERC20.py::test_transferFrom
tests/afelt/test_ERC20.py felt test_transferFrom
ExecutionResources(n_steps=905, builtin_instance_counter={'pedersen_builtin': 8, 'range_check_builtin': 25, 'ecdsa_builtin': 1, 'bitwise_builtin': 0, 'output_builtin': 0}, n_memory_holes=138)
Gas cost: 84.05000000000001Cost values from the results above are rounded-up:
| approve | transfer | transferFrom | |
|---|---|---|---|
| Uint256 | 56 | 85 | 115 |
| felt | 53 | 68 | 85 |
| savings (%) | 5.3 | 20 | 26 |
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