[stub] Investigate pickle serialization of Solution objects

Author: ischoegl

include/cantera/thermo/Phase.h

@@ -126,6 +126,9 @@ class Phase
      */
     void setXMLdata(XML_Node& xmlPhase);
 
+    //! write out XML tree information used for creation
+    std::string getXMLstring() const;
+
     /*! @name Name
      * Class Phase uses the string name to identify a phase. The name is the
      * value of the corresponding key in the phase map (in YAML), name (in

interfaces/cython/cantera/_cantera.pxd

@@ -156,6 +156,7 @@ cdef extern from "cantera/thermo/ThermoPhase.h" namespace "Cantera":
         size_t stateSize()
         void saveState(size_t, double*) except +translate_exception
         void restoreState(size_t, double*) except +translate_exception
+        string getXMLstring() except +translate_exception
 
         # initialization
         void addUndefinedElements() except +translate_exception

interfaces/cython/cantera/base.pyx

@@ -8,6 +8,18 @@ cdef class _SolutionBase:
                   source=None, yaml=None, thermo=None, species=(),
                   kinetics=None, reactions=(), **kwargs):
 
+        # run instantiation only if valid sources are specified
+        if origin or infile or source or (thermo and species):
+
+            self._cinit(infile=infile, name=name, adjacent=adjacent,
+                        origin=origin, source=source, yaml=yaml,
+                        thermo=thermo, species=species, kinetics=kinetics,
+                        reactions=reactions, **kwargs)
+
+    def _cinit(self, infile='', name='', adjacent=(), origin=None,
+                  source=None, yaml=None, thermo=None, species=(),
+                  kinetics=None, reactions=(), **kwargs):
+        
         if 'phaseid' in kwargs:
             if name is not '':
                 raise AttributeError('duplicate specification of phase name')
@@ -67,6 +79,7 @@ cdef class _SolutionBase:
         self._selected_species = np.ndarray(0, dtype=np.integer)
 
     def __init__(self, *args, **kwargs):
+
         if isinstance(self, Transport):
             assert self.transport is not NULL
 
@@ -225,8 +238,15 @@ cdef class _SolutionBase:
             for i,spec in enumerate(species):
                 self._selected_species[i] = self.species_index(spec)
 
-    def __reduce__(self):
-        raise NotImplementedError('Solution object is not picklable')
+    def __getstate__(self):
+        """Save complete information for pickling."""
+        return self.xml_string, self.ID, self.state
+
+    def __setstate__(self, pkl):
+        """Restore Solution from pickled information."""
+        xml, phaseid, state = pkl
+        self._cinit(source=xml, phaseid=phaseid)
+        self.state = state
 
     def __copy__(self):
         raise NotImplementedError('Solution object is not copyable')

interfaces/cython/cantera/test/test_thermo.py

@@ -667,10 +667,10 @@ def test_ref_info(self):
         self.assertNear(self.phase.min_temp, 300.0)
         self.assertNear(self.phase.max_temp, 3500.0)
 
-    def test_unpicklable(self):
-        import pickle
-        with self.assertRaises(NotImplementedError):
-            pickle.dumps(self.phase)
+    # def test_unpicklable(self):
+    #     import pickle
+    #     with self.assertRaises(NotImplementedError):
+    #         pickle.dumps(self.phase)
 
     def test_uncopyable(self):
         import copy

interfaces/cython/cantera/thermo.pyx

@@ -289,6 +289,11 @@ cdef class ThermoPhase(_SolutionBase):
         """
         return pystr(self.thermo.report(bool(show_thermo), threshold))
 
+    property xml_string:
+        """XML string used to create phase"""
+        def __get__(self):
+            return pystr(self.thermo.getXMLstring())
+
     def __call__(self, *args, **kwargs):
         print(self.report(*args, **kwargs))
 

src/thermo/Phase.cpp

@@ -66,6 +66,14 @@ void Phase::setXMLdata(XML_Node& xmlPhase)
     }
 }
 
+std::string Phase::getXMLstring() const
+{
+    std::ostringstream oss;
+    xml().writeHeader(oss);
+    xml().root().write(oss);
+    return oss.str();
+}
+
 std::string Phase::id() const
 {
     warn_deprecated("Phase::id",