Minor tweaks adding subproblem buffers and background vars to EVP

dedalus/core/problems.py

@@ -418,6 +418,9 @@ def build_EVP(self, eigenvalue=None, backgrounds=None, perturbations=None, **kw)
             # Add linearized equation and copy valid modes
             evp_eqn = EVP.add_equation((M + L - dF, 0))
             evp_eqn['valid_modes'][:] = eqn['valid_modes']
+        # Add backgrounds to EVP namespace
+        for var in backgrounds:
+            EVP.local_namespace[var.name] = var
         return EVP
 
 

dedalus/core/subsystems.py

@@ -262,8 +262,12 @@ def __init__(self, solver, subsystems, group):
         # Build input and output buffers and views, except for EVPs
         from .problems import EigenvalueProblem
         if not isinstance(problem, EigenvalueProblem):
-            self._input_buffer, self._input_views = self._build_buffer_views(self.problem.LHS_variables)
-            self._output_buffer, self._output_views = self._build_buffer_views([eqn['F'] for eqn in problem.equations])
+            self._build_buffers()
+
+    def _build_buffers(self):
+        self._input_buffer, self._input_views = self._build_buffer_views(self.problem.LHS_variables)
+        if 'F' in self.problem.equations[0]:
+            self._output_buffer, self._output_views = self._build_buffer_views([eqn['F'] for eqn in self.problem.equations])
 
     @CachedAttribute
     def shape(self):