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| 1 | +#!/usr/bin/env python3 |
| 2 | +""" |
| 3 | +Независимый второй свидетель для GF14 (строгий SW-bitexact). |
| 4 | +
|
| 5 | +НЕ переиспользует generator/encoder. Декодер написан с нуля по параметрам |
| 6 | +каталога SSOT (specs/numeric/gf14.t27 -> bits=14 s=1 e=5 m=8 bias=15 storage=u16), |
| 7 | +с точной рациональной арифметикой (fractions.Fraction) -> abs_error == 0. |
| 8 | +
|
| 9 | +Соответствие honesty-rules: |
| 10 | +- фиксированный детерминированный bit-layout: [sign:1][exp:5][mant:8] (LSB-aligned в u16); |
| 11 | +- второй независимый закон decode (этот файл) против вектор-значений из пака; |
| 12 | +- сравнение точное (Fraction), не float-приближение. |
| 13 | +
|
| 14 | +Запуск: python3 gf14_independent_witness.py conformance/vectors/gf14_conformance_v0.json |
| 15 | +Выход: 0 = все 14 совпали abs_error=0; 1 = расхождение. |
| 16 | +""" |
| 17 | +import json |
| 18 | +import sys |
| 19 | +from fractions import Fraction |
| 20 | + |
| 21 | +# --- параметры GF14 из каталога SSOT (НЕ из generator) --- |
| 22 | +EXP_BITS = 5 |
| 23 | +MANT_BITS = 8 |
| 24 | +BIAS = 15 |
| 25 | +EXP_MAX = (1 << EXP_BITS) - 1 # 31 = all-ones -> Inf/NaN |
| 26 | +MANT_MAX = (1 << MANT_BITS) - 1 # 255 |
| 27 | +TOTAL_BITS = 1 + EXP_BITS + MANT_BITS # 14 |
| 28 | + |
| 29 | + |
| 30 | +def decode_exact(raw): |
| 31 | + """Независимый decode -> Fraction (или строка для Inf/NaN/zero-sign).""" |
| 32 | + raw &= (1 << TOTAL_BITS) - 1 # маска 14 значащих бит |
| 33 | + sign = (raw >> (EXP_BITS + MANT_BITS)) & 1 |
| 34 | + exp = (raw >> MANT_BITS) & EXP_MAX |
| 35 | + mant = raw & MANT_MAX |
| 36 | + |
| 37 | + if exp == EXP_MAX: # спец-класс |
| 38 | + if mant == 0: |
| 39 | + return "INF(-)" if sign else "INF(+)" |
| 40 | + return "NAN(-)" if sign else "NAN(+)" |
| 41 | + |
| 42 | + if exp == 0: # zero / subnormal |
| 43 | + if mant == 0: |
| 44 | + return "ZERO(-)" if sign else "ZERO(+)" |
| 45 | + # subnormal: mant/2^m * 2^(1-bias) |
| 46 | + val = Fraction(mant, 1 << MANT_BITS) * Fraction(2) ** (1 - BIAS) |
| 47 | + else: # normal: (1 + mant/2^m) * 2^(exp-bias) |
| 48 | + val = (1 + Fraction(mant, 1 << MANT_BITS)) * Fraction(2) ** (exp - BIAS) |
| 49 | + |
| 50 | + return -val if sign else val |
| 51 | + |
| 52 | + |
| 53 | +def parse_expected(value_str): |
| 54 | + """Ожидаемое значение из пака -> Fraction или маркер-строка.""" |
| 55 | + s = value_str.strip() |
| 56 | + if s in ("INF(+)", "INF(-)", "NAN(+)", "NAN(-)"): |
| 57 | + return s |
| 58 | + if s in ("0", "-0", "+0"): |
| 59 | + return Fraction(0) |
| 60 | + # десятичная дробь -> точная Fraction через строку |
| 61 | + return Fraction(s) |
| 62 | + |
| 63 | + |
| 64 | +def main(path): |
| 65 | + pack = json.load(open(path)) |
| 66 | + vecs = pack["vectors"] |
| 67 | + assert pack["format"].upper().startswith("GF14"), "не GF14-пак" |
| 68 | + ok = 0 |
| 69 | + fails = [] |
| 70 | + for v in vecs: |
| 71 | + raw = int(v["hex"], 16) |
| 72 | + # перекрёстная проверка bits == hex |
| 73 | + if v.get("bits") is not None and v["bits"] != raw: |
| 74 | + fails.append((v["label"], f"bits!=hex: {v['bits']} vs {raw}")) |
| 75 | + continue |
| 76 | + got = decode_exact(raw) |
| 77 | + exp = parse_expected(v["value"]) |
| 78 | + |
| 79 | + if isinstance(exp, str): # спец-класс: сравниваем по классу/знаку |
| 80 | + # zero: пак пишет "0" -> допускаем оба знака нуля |
| 81 | + if exp in ("INF(+)", "INF(-)", "NAN(+)", "NAN(-)"): |
| 82 | + match = (got == exp) |
| 83 | + else: |
| 84 | + match = isinstance(got, str) and got.startswith("ZERO") |
| 85 | + else: |
| 86 | + if isinstance(got, str): # got спец, exp число |
| 87 | + match = (exp == 0 and got.startswith("ZERO")) |
| 88 | + else: |
| 89 | + match = (Fraction(got) == exp) # ТОЧНОЕ равенство, abs_error=0 |
| 90 | + |
| 91 | + if match: |
| 92 | + ok += 1 |
| 93 | + else: |
| 94 | + fails.append((v["label"], f"got={got} exp={exp}")) |
| 95 | + |
| 96 | + print(f"GF14 independent witness: {ok}/{len(vecs)} bit-exact (abs_error=0)") |
| 97 | + if fails: |
| 98 | + print("FAILS:") |
| 99 | + for lbl, msg in fails: |
| 100 | + print(f" {lbl}: {msg}") |
| 101 | + return 1 |
| 102 | + print("VERDICT: gf14 promotable selfconsistent -> strict bitexact (2nd independent witness OK)") |
| 103 | + return 0 |
| 104 | + |
| 105 | + |
| 106 | +if __name__ == "__main__": |
| 107 | + p = sys.argv[1] if len(sys.argv) > 1 else "conformance/vectors/gf14_conformance_v0.json" |
| 108 | + sys.exit(main(p)) |
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