84 lines
2.4 KiB
Python
84 lines
2.4 KiB
Python
from itertools import product as iproduct
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from tea3.tea3model import Tea3Model
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from tea3.pretty_print import pretty_print
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def count_monomials(poly):
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s = pretty_print(poly).strip()
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if not s or s == "0":
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return 0
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return sum(1 for term in s.split("+") if term.strip())
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def apply_variable_change(model, coeffs):
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"""
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Variable change inside each 8-bit register:
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x_{r,0} = y_{r,0} + a1*y_{r,1} + ... + a7*y_{r,7}
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x_{r,j} = y_{r,j} for j = 1..7
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for every register r in {0,...,4}.
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"""
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orig_x = [list(model.v[r * 8 : (r + 1) * 8]) for r in range(5)]
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orig_y = model.y_bits
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subs = {}
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for r in range(5):
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for j in range(1, 8):
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subs[orig_x[r][j]] = orig_y[r][j]
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new_expr = orig_y[r][0]
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for j, ai in enumerate(coeffs, start=1):
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if ai:
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new_expr += orig_y[r][j]
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subs[orig_x[r][0]] = new_expr
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new_R = []
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for i in range(8):
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row = [poly.subs(subs) for poly in model.R_bits[i]]
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new_R.append(row)
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return new_R
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def run_exhaustive(steps: int, target_reg: int = 0, target_bit: int = -1):
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model = Tea3Model()
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for _ in range(steps):
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model.step()
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snapshot = model
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if target_bit == -1:
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bits = list(range(8))
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else:
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if not (0 <= target_bit < 8):
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raise ValueError("target_bit must be in [0, 7] or -1")
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bits = [target_bit]
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best_coeffs: tuple | None = None
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best_total: int = -1
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best_R: list | None = None
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for idx, coeffs in enumerate(iproduct([0, 1], repeat=7)):
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new_R = apply_variable_change(snapshot, coeffs)
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label = "".join(map(str, coeffs))
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print(f"\n[{idx:03d}] (a1,a2,a3,a4,a5,a6,a7) = {label}")
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total = 0
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for j in bits:
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poly = new_R[target_reg][j]
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pp = pretty_print(poly)
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print(f" R[{target_reg}][{j}] = {pp}")
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total += count_monomials(poly)
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if best_total == -1 or total < best_total:
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best_total = total
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best_coeffs = coeffs
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best_R = new_R
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print("\nBest variable change (fewest total monomials)")
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print(f" (a1,a2,a3,a4,a5,a6,a7) = ({', '.join(map(str, best_coeffs))})")
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print(f" Total monomials: {best_total}")
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print(" Polynomial:\n")
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for j in bits:
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poly = best_R[target_reg][j]
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print(f"R[{target_reg}][{j}] = {pretty_print(poly)}")
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