api: enforce sympy shifts

devito/finite_differences/tools.py

@@ -2,7 +2,7 @@
 from itertools import product
 
 import numpy as np
-from sympy import S, finite_diff_weights, cacheit, sympify, Function
+from sympy import S, finite_diff_weights, cacheit, sympify, Function, Rational
 
 from devito.tools import Tag, as_tuple
 from devito.types.dimension import StencilDimension
@@ -308,13 +308,13 @@ def make_shift_x0(shift, ndim):
     """
     if shift is None:
         return lambda s, d, i, j: None
-    elif isinstance(shift, float):
-        return lambda s, d, i, j: d + s * d.spacing
+    elif sympify(shift).is_Number:
+        return lambda s, d, i, j: d + Rational(s) * d.spacing
     elif type(shift) is tuple and np.shape(shift) == ndim:
         if len(ndim) == 1:
-            return lambda s, d, i, j: d + s[j] * d.spacing
+            return lambda s, d, i, j: d + Rational(s[j]) * d.spacing
         elif len(ndim) == 2:
-            return lambda s, d, i, j: d + s[i][j] * d.spacing
+            return lambda s, d, i, j: d + Rational(s[i][j]) * d.spacing
         else:
             raise ValueError("ndim length must be equal to 1 or 2")
     raise ValueError("shift parameter must be one of the following options: "

devito/symbolics/printer.py

@@ -7,6 +7,8 @@
 
 from mpmath.libmp import prec_to_dps, to_str
 from packaging.version import Version
+
+from sympy.codegen.ast import float32, float64
 from sympy.logic.boolalg import BooleanFunction
 from sympy.printing.precedence import PRECEDENCE_VALUES, precedence
 from sympy.printing.c import C99CodePrinter
@@ -18,6 +20,9 @@
 __all__ = ['ccode']
 
 
+_type_mapper = {np.float32: float32, np.float64: float64}
+
+
 class CodePrinter(C99CodePrinter):
 
     """
@@ -179,12 +184,20 @@ def _print_Add(self, expr, order=None):
 
     def _print_Float(self, expr):
         """Print a Float in C-like scientific notation."""
+        try:
+            # Make sure the float is in the correct format
+            expr = _type_mapper[self.dtype].cast_nocheck(expr)
+            rv = str(expr)
+        except KeyError:
+            pass
+
         prec = expr._prec
 
         if prec < 5:
             dps = 0
         else:
             dps = prec_to_dps(expr._prec)
+
         if self._settings["full_prec"] is True:
             strip = False
         elif self._settings["full_prec"] is False:

tests/test_tensors.py

@@ -1,5 +1,6 @@
 import numpy as np
 import sympy
+from sympy import Rational
 
 import pytest
 
@@ -383,8 +384,8 @@ def test_shifted_lap_of_tensor(shift, ndim):
         for j in range(ndim):
             ref = 0
             for i, d in enumerate(v.space_dimensions):
-                x0 = (None if shift is None else d + shift[i][j] * d.spacing if
-                      type(shift) is tuple else d + shift * d.spacing)
+                x0 = (None if shift is None else d + Rational(shift[i][j]) * d.spacing if
+                      type(shift) is tuple else d + Rational(shift) * d.spacing)
                 ref += getattr(v[j, i], 'd%s2' % d.name)(x0=x0, fd_order=order)
             assert df[j] == ref