Fix BCH/RS decoder caching bug

src/galois/_codes/_bch.py

@@ -661,7 +661,7 @@ def decode(self, codeword, output="message", errors=False):
  return super().decode(codeword, output=output, errors=errors)
 
  def _decode_codeword(self, codeword: FieldArray) -> tuple[FieldArray, np.ndarray]:
- func = decode_jit(self.field, self.extension_field)
+ func = bch_decode_jit(self.field, self.extension_field)
  dec_codeword, N_errors = func(codeword, self.n, int(self.alpha), self.c, self.roots)
  dec_codeword = dec_codeword.view(self.field)
  return dec_codeword, N_errors
@@ -1192,7 +1192,7 @@ def _generator_poly_from_k(
  return best_generator_poly, best_roots
 
 
-class decode_jit(Function):
+class bch_decode_jit(Function):
  """
  Performs general BCH and Reed-Solomon decoding.
 
@@ -1204,6 +1204,18 @@ def __init__(self, field: Type[FieldArray], extension_field: Type[FieldArray]):
  super().__init__(field)
  self.extension_field = extension_field
 
+ @property
+ def key_1(self):
+ # Make the key in the cache lookup table specific to both the base field and extension field
+ return (
+ self.field.characteristic,
+ self.field.degree,
+ int(self.field.irreducible_poly),
+ self.extension_field.characteristic,
+ self.extension_field.degree,
+ int(self.extension_field.irreducible_poly),
+ )
+
  def __call__(self, codeword, design_n, alpha, c, roots):
  if self.extension_field.ufunc_mode != "python-calculate":
  output = self.jit(codeword.astype(np.int64), design_n, alpha, c, roots.astype(np.int64))

src/galois/_codes/_reed_solomon.py

@@ -13,7 +13,7 @@
 from .._math import ilog
 from .._polys import Poly, matlab_primitive_poly
 from ..typing import ArrayLike, ElementLike
-from ._bch import decode_jit
+from ._bch import bch_decode_jit
 from ._cyclic import _CyclicCode
 
 
@@ -613,7 +613,7 @@ def decode(self, codeword, output="message", errors=False):
  return super().decode(codeword, output=output, errors=errors)
 
  def _decode_codeword(self, codeword: FieldArray) -> tuple[FieldArray, np.ndarray]:
- func = decode_jit(self.field, self.field)
+ func = reed_solomon_decode_jit(self.field, self.field)
  dec_codeword, N_errors = func(codeword, self.n, int(self.alpha), self.c, self.roots)
  dec_codeword = dec_codeword.view(self.field)
  return dec_codeword, N_errors
@@ -1033,3 +1033,14 @@ def is_narrow_sense(self) -> bool:
  @property
  def is_systematic(self) -> bool:
  return super().is_systematic
+
+
+class reed_solomon_decode_jit(bch_decode_jit):
+ """
+ Performs general BCH and Reed-Solomon decoding.
+
+ References:
+ - Lin, S. and Costello, D. Error Control Coding. Section 7.4.
+ """
+
+ # NOTE: Making a subclass so that these compiled functions are stored in a new namespace

src/galois/_domains/_function.py

@@ -56,6 +56,18 @@ def set_globals(self):
  # Various ufuncs based on implementation and compilation
  ###############################################################################
 
+ @property
+ def key_1(self):
+ return (self.field.characteristic, self.field.degree, int(self.field.irreducible_poly))
+
+ @property
+ def key_2(self):
+ if self.field.ufunc_mode == "jit-lookup":
+ key = (str(self.__class__), self.field.ufunc_mode, int(self.field.primitive_element))
+ else:
+ key = (str(self.__class__), self.field.ufunc_mode)
+ return key
+
  @property
  def function(self):
  """
@@ -72,19 +84,13 @@ def jit(self) -> numba.types.FunctionType:
  """
  assert self.field.ufunc_mode in ["jit-lookup", "jit-calculate"]
 
- key_1 = (self.field.characteristic, self.field.degree, int(self.field.irreducible_poly))
- if self.field.ufunc_mode == "jit-lookup":
- key_2 = (str(self.__class__), self.field.ufunc_mode, int(self.field.primitive_element))
- else:
- key_2 = (str(self.__class__), self.field.ufunc_mode)
- self._CACHE.setdefault(key_1, {})
-
- if key_2 not in self._CACHE[key_1]:
+ self._CACHE.setdefault(self.key_1, {})
+ if self.key_2 not in self._CACHE[self.key_1]:
  self.set_globals() # Set the globals once before JIT compiling the function
  func = numba.jit(self._SIGNATURE.signature, parallel=self._PARALLEL, nopython=True)(self.implementation)
- self._CACHE[key_1][key_2] = func
+ self._CACHE[self.key_1][self.key_2] = func
 
- return self._CACHE[key_1][key_2]
+ return self._CACHE[self.key_1][self.key_2]
 
  @property
  def python(self) -> Callable:

tests/codes/test_bch.py

@@ -378,3 +378,17 @@ def test_bch_valid_codes_511():
  code = random.choice(codes)
  bch = galois.BCH(code[0], code[1])
  assert (bch.n, bch.k, bch.t) == code
+
+
+def test_bug_483():
+ """
+ See https://github.com/mhostetter/galois/issues/483.
+ """
+ bch_1 = galois.BCH(15, 11)
+ verify_decode(bch_1, 1)
+
+ bch_2 = galois.BCH(7, 4)
+ verify_decode(bch_2, 1)
+
+ bch_3 = galois.BCH(31, 26)
+ verify_decode(bch_3, 1)