starknet-tokens-showdown

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 uint one is a copy of OpenZeppelin's ERC20, v0.3.1
• the afelt one is based on the OZ token with a slight modification of completely dropping the use of Uint256 and replacing if with felts 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:

approve

# 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

transfer

# 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

transferFrom

# 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: 84.05000000000001

Results

Cost values from the results above are rounded-up:

	approve	transfer	transferFrom
Uint256	56	85	115
felt	53	68	85
savings (%)	5.3	20	26