Created
October 6, 2020 19:12
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#!/usr/bin/python3 | |
import json | |
import math | |
# New EIP | |
def calculate_multiplication_complexity(base_length, modulus_length): | |
max_length = max(base_length, modulus_length) | |
words = math.ceil(max_length / 8) | |
return words**2 | |
def calculate_iteration_count(exponent_length, exponent): # same as ADUSTED_EXPONENT_LENGTH in EIP-198 | |
iteration_count = 0 | |
if exponent_length <= 32 and exponent == 0: iteration_count = 0 | |
elif exponent_length <= 32: iteration_count = exponent.bit_length() - 1 | |
elif exponent_length > 32: iteration_count = (8 * (exponent_length - 32)) + ((exponent & (2**256 - 1)).bit_length() - 1) | |
return max(iteration_count, 1) | |
def calculate_gas_cost(base_length, modulus_length, exponent_length, exponent): | |
multiplication_complexity = calculate_multiplication_complexity(base_length, modulus_length) | |
iteration_count = calculate_iteration_count(exponent_length, exponent) | |
return max(200, math.floor(multiplication_complexity * iteration_count / 3)) | |
# Orig EIP 198 | |
def calculate_old_multiplication_complexity(x): | |
if x <= 64: return x ** 2 | |
elif x <= 1024: return ((x ** 2) // 4) + ((96 * x) - 3072) | |
else: return ((x ** 2) // 16) + ((480 * x) - 199680) | |
def calculate_old_gas_cost(base_length, modulus_length, exponent_length, exponent): | |
GQUADDIVISOR = 20 | |
mul_complex = calculate_old_multiplication_complexity(max(base_length, modulus_length)) | |
adj_exp_len = calculate_iteration_count(exponent_length, exponent) | |
return math.floor(mul_complex * max(adj_exp_len, 1) / GQUADDIVISOR) | |
# Download EIP-198 test vectors - wget https://raw.githubusercontent.com/ethereum/go-ethereum/master/core/vm/testdata/precompiles/modexp.json | |
f = open('modexp.json') | |
vectors = json.load(f) | |
print("{:22} {:8} {:8} {:8}".format('Name', 'Old Gas', 'Exp old', 'New Gas')) | |
for v in vectors: | |
baselen = int(v['Input'][0:64], 16) | |
explen = int(v['Input'][64:128], 16) | |
modlen = int(v['Input'][128:192], 16) | |
exp = int(v['Input'][(192 + (baselen * 2)):(192 + ((baselen + explen) * 2))], 16) | |
old_gas = calculate_old_gas_cost(baselen, modlen, explen, exp) | |
exp_old_gas = v['Gas'] | |
new_gas = calculate_gas_cost(baselen, modlen, explen, exp) | |
print("{:22} {:8} {:8} {:8}".format(v['Name'], old_gas, exp_old_gas, new_gas)) |
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