test_amortized_bn128_pairings()

Documentation for tests/zkevm/test_worst_compute.py::test_amortized_bn128_pairings@64f949d0.

Generate fixtures for these test cases for Prague with:

fill -v tests/zkevm/test_worst_compute.py::test_amortized_bn128_pairings --fork Prague

Test running a block with as many BN128 pairings as possible.

Source code in tests/zkevm/test_worst_compute.py

@pytest.mark.valid_from("Cancun")
@pytest.mark.slow()
def test_amortized_bn128_pairings(
    state_test: StateTestFiller,
    pre: Alloc,
    fork: Fork,
):
    """Test running a block with as many BN128 pairings as possible."""
    env = Environment()

    base_cost = 45_000
    pairing_cost = 34_000
    size_per_pairing = 192

    gsc = fork.gas_costs()
    intrinsic_gas_calculator = fork.transaction_intrinsic_cost_calculator()
    mem_exp_gas_calculator = fork.memory_expansion_gas_calculator()

    # This is a theoretical maximum number of pairings that can be done in a block.
    # It is only used for an upper bound for calculating the optimal number of pairings below.
    maximum_number_of_pairings = (env.gas_limit - base_cost) // pairing_cost

    # Discover the optimal number of pairings balancing two dimensions:
    # 1. Amortize the precompile base cost as much as possible.
    # 2. The cost of the memory expansion.
    max_pairings = 0
    optimal_per_call_num_pairings = 0
    for i in range(1, maximum_number_of_pairings + 1):
        # We'll pass all pairing arguments via calldata.
        available_gas_after_intrinsic = env.gas_limit - intrinsic_gas_calculator(
            calldata=[0xFF] * size_per_pairing * i  # 0xFF is to indicate non-zero bytes.
        )
        available_gas_after_expansion = max(
            0,
            available_gas_after_intrinsic - mem_exp_gas_calculator(new_bytes=i * size_per_pairing),
        )

        # This is ignoring "glue" opcodes, but helps to have a rough idea of the right
        # cutting point.
        approx_gas_cost_per_call = gsc.G_WARM_ACCOUNT_ACCESS + base_cost + i * pairing_cost

        num_precompile_calls = available_gas_after_expansion // approx_gas_cost_per_call
        num_pairings_done = num_precompile_calls * i  # Each precompile call does i pairings.

        if num_pairings_done > max_pairings:
            max_pairings = num_pairings_done
            optimal_per_call_num_pairings = i

    calldata = Op.CALLDATACOPY(size=Op.CALLDATASIZE)
    attack_block = Op.POP(Op.STATICCALL(Op.GAS, 0x08, 0, Op.CALLDATASIZE, 0, 0))
    code = code_loop_precompile_call(calldata, attack_block, fork)

    code_address = pre.deploy_contract(code=code)

    tx = Transaction(
        to=code_address,
        gas_limit=env.gas_limit,
        data=_generate_bn128_pairs(optimal_per_call_num_pairings, 42),
        sender=pre.fund_eoa(),
    )

    state_test(
        env=env,
        pre=pre,
        post={},
        tx=tx,
    )

Parametrized Test Cases

This test case is only parametrized by fork and fixture format.

Fork All Forks Cancun Prague Osaka

Fixture Type All Fixture Types state_test blockchain_test

Test ID (Abbreviated)
...fork_Cancun-state_test
...fork_Cancun-blockchain_test_from_state_test
...fork_Prague-state_test
...fork_Prague-blockchain_test_from_state_test
...fork_Osaka-state_test
...fork_Osaka-blockchain_test_from_state_test