Make sympy code optimizations optional (#1878)

Turns out that applying sympy optimizations as introduced
in #1377 is
potentially very costly. Therefore, they are disabled by
default. They can be enabled by setting
`AmiciCxxCodePrinter.optimizations` as shown in the test
case.

python/sdist/amici/cxxcodeprinter.py

@@ -2,19 +2,34 @@
 import itertools
 import os
 import re
-from typing import Dict, List, Optional, Tuple
+from typing import Dict, List, Optional, Tuple, Iterable
 
 import sympy as sp
-from sympy.codegen.rewriting import optimize, optims_c99
+from sympy.codegen.rewriting import optimize, Optimization
 from sympy.printing.cxx import CXX11CodePrinter
 from sympy.utilities.iterables import numbered_symbols
 from toposort import toposort
 
 
 class AmiciCxxCodePrinter(CXX11CodePrinter):
-    """C++ code printer"""
+    """
+    C++ code printer
+
+    Attributes
+    ----------
+    extract_cse:
+        Whether to extract common subexpression during code printing.
+        Currently controlled by environment variable ``AMICI_EXTRACT_CSE``.
+    optimizations:
+        Iterable of :class:`sympy.codegen.rewriting.Optimization`s to optimize
+        generated code (e.g. :data:`sympy.codegen.rewriting.Optimization` for
+        optimizations, such as ``log(1 + x)`` --> ``logp1(x)``).
+        Applying these optimizations is potentially quite costly.
+    """
+
+    optimizations: Iterable[Optimization] = ()
 
-    def __init__(self, optimize_code: bool = True):
+    def __init__(self):
         """
         Create code printer
 
@@ -29,8 +44,8 @@ def __init__(self, optimize_code: bool = True):
 
         # Floating-point optimizations
         # e.g., log(1 + x) --> logp1(x)
-        if optimize_code:
-            self._fpoptimizer = lambda x: optimize(x, optims_c99)
+        if self.optimizations:
+            self._fpoptimizer = lambda x: optimize(x, self.optimizations)
         else:
             self._fpoptimizer = None
 

python/tests/test_cxxcodeprinter.py

@@ -0,0 +1,14 @@
+from amici.cxxcodeprinter import AmiciCxxCodePrinter
+from sympy.codegen.rewriting import optims_c99
+import sympy as sp
+
+
+def test_optimizations():
+    """Check that AmiciCxxCodePrinter handles optimizations correctly."""
+    try:
+        old_optim = AmiciCxxCodePrinter.optimizations
+        AmiciCxxCodePrinter.optimizations = optims_c99
+        cp = AmiciCxxCodePrinter()
+        assert "expm1" in cp.doprint(sp.sympify("exp(x) - 1"))
+    finally:
+        AmiciCxxCodePrinter.optimizations = old_optim