api: avoid duplicate deprecation warnings

devito/deprecations.py

@@ -0,0 +1,15 @@
+from functools import cached_property
+from warnings import warn
+
+
+class DevitoDeprecation():
+
+    @cached_property
+    def coeff_warn(self):
+        warn("The Coefficient API is deprecated and will be removed, coefficients should"
+             "be passed directly to the derivative object `u.dx(weights=...)",
+             DeprecationWarning, stacklevel=2)
+        return
+
+
+deprecations = DevitoDeprecation()

devito/finite_differences/coefficients.py

@@ -1,13 +1,11 @@
-from warnings import warn
+from devito.deprecations import deprecations
 
 __all__ = ['Coefficient', 'Substitutions']
 
 
 class Coefficient:
     def __init__(self, deriv_order, function, dimension, weights):
-        warn("The Coefficient API is deprecated and will be removed, coefficients should"
-             "be passed directly to the derivative object `u.dx(weights=...)",
-             DeprecationWarning, stacklevel=2)
+        deprecations.coeff_warn
         self._weights = weights
         self._deriv_order = deriv_order
         self._function = function
@@ -36,9 +34,7 @@ def weights(self):
 
 class Substitutions:
     def __init__(self, *args):
-        warn("The Coefficient API is deprecated and will be removed, coefficients should"
-             "be passed directly to the derivative object `u.dx(weights=...)",
-             DeprecationWarning, stacklevel=2)
+        deprecations.coeff_warn
         if any(not isinstance(arg, Coefficient) for arg in args):
             raise TypeError("Non Coefficient object within input")
 

devito/finite_differences/tools.py

@@ -278,7 +278,10 @@ def generate_indices(expr, dim, order, side=None, matvec=None, x0=None, nweights
             o_min -= 1
 
     if nweights > 0 and (o_max - o_min + 1) != nweights:
+        # We cannot infer how the stencil should be centered
+        # if nweights is more than one extra point.
         assert nweights == (o_max - o_min + 1) + 1
+        # In the "one extra" case  we need to pad with one point to symmetrize
         if (o_max - mid) > (mid - o_min):
             o_min -= 1
         else:

devito/types/equation.py

@@ -1,8 +1,7 @@
 """User API to specify equations."""
-from warnings import warn
-
 import sympy
 
+from devito.deprecations import deprecations
 from devito.tools import as_tuple, frozendict
 from devito.types.lazy import Evaluable
 
@@ -64,15 +63,14 @@ class Eq(sympy.Eq, Evaluable):
     def __new__(cls, lhs, rhs=0, subdomain=None, coefficients=None, implicit_dims=None,
                 **kwargs):
         if coefficients is not None:
-            warn("The Substitution API is deprecated and will be removed, "
-                 "coefficients should be passed directly to the derivative object"
-                 " i.e `u.dx(weights=...)",
-                 DeprecationWarning, stacklevel=2)
+            deprecations.coeff_warn
         kwargs['evaluate'] = False
-        # Backward compat
+        # Backward compatibility
         rhs = cls._apply_coeffs(rhs, coefficients)
         lhs = cls._apply_coeffs(lhs, coefficients)
+
         obj = sympy.Eq.__new__(cls, lhs, rhs, **kwargs)
+
         obj._subdomain = subdomain
         obj._substitutions = coefficients
         obj._implicit_dims = as_tuple(implicit_dims)
@@ -82,7 +80,7 @@ def __new__(cls, lhs, rhs=0, subdomain=None, coefficients=None, implicit_dims=No
     @classmethod
     def _apply_coeffs(cls, expr, coefficients):
         """
-        This process legacy API of Substitution/Coefficients applying the weights
+        This processes legacy API of Substitution/Coefficients applying the weights
         to the target Derivatives.
         """
         from devito.symbolics import retrieve_derivatives