[SpeciesThermo] assign nCoeffs in C++ layer

include/cantera/thermo/ConstCpPoly.h

@@ -86,6 +86,9 @@ public:
     void updatePropertiesTemp(const doublereal temp,
                               doublereal* cp_R, doublereal* h_RT,
                               doublereal* s_R) const;
+
+    size_t nCoeffs() const { return 4; }
+
     void reportParameters(size_t& n, int& type,
                           doublereal& tlow, doublereal& thigh,
                           doublereal& pref,

include/cantera/thermo/Mu0Poly.h

@@ -127,6 +127,9 @@ public:
                                       doublereal* cp_R,
                                       doublereal* h_RT,
                                       doublereal* s_R) const;
+
+    virtual size_t nCoeffs() const;
+
     virtual void reportParameters(size_t& n, int& type,
                                   doublereal& tlow, doublereal& thigh,
                                   doublereal& pref,

include/cantera/thermo/Nasa9PolyMultiTempRegion.h

@@ -75,6 +75,8 @@ public:
                                       doublereal* cp_R, doublereal* h_RT,
                                       doublereal* s_R) const;
 
+    virtual size_t nCoeffs() const;
+
     //! This utility function reports back the type of parameterization and all
     //! of the parameters for the species, index.
     /*!

include/cantera/thermo/NasaPoly2.h

@@ -123,6 +123,8 @@ public:
         }
     }
 
+    size_t nCoeffs() const { return 15; }
+
     void reportParameters(size_t& n, int& type,
                           doublereal& tlow, doublereal& thigh,
                           doublereal& pref,

include/cantera/thermo/ShomatePoly.h

@@ -306,6 +306,8 @@ public:
         }
     }
 
+    virtual size_t nCoeffs() const { return 15; }
+
     virtual void reportParameters(size_t& n, int& type,
                                   doublereal& tlow, doublereal& thigh,
                                   doublereal& pref,

include/cantera/thermo/SpeciesThermoInterpType.h

@@ -206,6 +206,12 @@ public:
                                       doublereal* h_RT,
                                       doublereal* s_R) const;
 
+
+    //! This utility function reports back the number of coefficients
+    //! for a given type of species parameterization
+    virtual size_t nCoeffs() const;
+
+
     //! This utility function reports back the type of parameterization and all
     //! of the parameters for the species.
     /*!

interfaces/cython/cantera/_cantera.pxd

@@ -96,6 +96,7 @@ cdef extern from "cantera/thermo/SpeciesThermoInterpType.h":
         double maxTemp()
         double refPressure()
         void reportParameters(size_t&, int&, double&, double&, double&, double* const) except +translate_exception
+        int nCoeffs() except +translate_exception
 
 cdef extern from "cantera/thermo/SpeciesThermoFactory.h":
     cdef CxxSpeciesThermo* CxxNewSpeciesThermo "Cantera::newSpeciesThermoInterpType"\

interfaces/cython/cantera/speciesthermo.pyx

@@ -32,7 +32,7 @@ cdef class SpeciesThermo:
         if not init:
             return
 
-        if len(coeffs) != self.n_coeffs:
+        if not self.check_n_coeffs(len(coeffs)):
             raise ValueError("Coefficient array has incorrect length")
         cdef np.ndarray[np.double_t, ndim=1] data = np.ascontiguousarray(
             coeffs, dtype=np.double)
@@ -59,6 +59,11 @@ cdef class SpeciesThermo:
         def __get__(self):
             return self.spthermo.refPressure()
 
+    property n_coeffs:
+        """ Number of parameters for the parameterization."""
+        def __get__(self):
+            return self.spthermo.nCoeffs()
+
     property coeffs:
         """
         Array of coefficients for the parameterization. The length of this
@@ -74,6 +79,9 @@ cdef class SpeciesThermo:
                                            T_high, P_ref, &data[0])
             return data
 
+    def check_n_coeffs(self, n):
+        raise NotImplementedError('Needs to be overloaded')
+
     def cp(self, T):
         """
         Molar heat capacity at constant pressure [J/kmol/K] at temperature *T*.
@@ -109,13 +117,15 @@ cdef class ConstantCp(SpeciesThermo):
              - `coeffs[3]` = :math:`c_p^o(T_0, p_{ref})` [J/kmol-K]
     """
     derived_type = SPECIES_THERMO_CONSTANT_CP
-    n_coeffs = 4
+
+    def check_n_coeffs(self, n):
+        return n == 4
 
 
 cdef class Mu0Poly(SpeciesThermo):
     """
     Thermodynamic properties for a species which is parameterized using an
-    interpolation of the Gibbs free energy based on a piecewise constant heat 
+    interpolation of the Gibbs free energy based on a piecewise constant heat
     capacity approximation. This is a wrapper for the C++ class :ct:`Mu0Poly`.
 
     :param coeffs:
@@ -130,7 +140,9 @@ cdef class Mu0Poly(SpeciesThermo):
             - ...
     """
     derived_type = SPECIES_THERMO_MU0_INTERP
-    n_coeffs = 2
+
+    def check_n_coeffs(self, n):
+        return n > 3 and n % 2 == 0
 
 
 cdef class NasaPoly2(SpeciesThermo):
@@ -153,13 +165,15 @@ cdef class NasaPoly2(SpeciesThermo):
         input files.
     """
     derived_type = SPECIES_THERMO_NASA2
-    n_coeffs = 15
+
+    def check_n_coeffs(self, n):
+        return n == 15
 
 
 cdef class Nasa9PolyMultiTempRegion(SpeciesThermo):
     """
     Thermodynamic properties for a species which is parameterized using the
-    9-coefficient NASA polynomial form encompassing multiple temperature ranges. 
+    9-coefficient NASA polynomial form encompassing multiple temperature ranges.
     This is a wrapper for the C++ class :ct:`Nasa9PolyMultiTempRegion`.
 
     :param coeffs:
@@ -176,7 +190,9 @@ cdef class Nasa9PolyMultiTempRegion(SpeciesThermo):
         as in the NIST Chemistry WebBook).
     """
     derived_type = SPECIES_THERMO_NASA9MULTITEMP
-    n_coeffs = 11
+
+    def check_n_coeffs(self, n):
+        return n > 11 and ((n - 1) % 11) == 0
 
 
 cdef class ShomatePoly2(SpeciesThermo):
@@ -200,7 +216,9 @@ cdef class ShomatePoly2(SpeciesThermo):
         as in the NIST Chemistry WebBook).
     """
     derived_type = SPECIES_THERMO_SHOMATE2
-    n_coeffs = 15
+
+    def check_n_coeffs(self, n):
+        return n == 15
 
 
 cdef wrapSpeciesThermo(shared_ptr[CxxSpeciesThermo] spthermo):

src/thermo/Mu0Poly.cpp

@@ -129,6 +129,11 @@ void Mu0Poly::updatePropertiesTemp(const doublereal T,
     updateProperties(&T, cp_R, h_RT, s_R);
 }
 
+size_t Mu0Poly::nCoeffs() const
+{
+    return 2*m_numIntervals + 2;
+}
+
 void Mu0Poly::reportParameters(size_t& n, int& type,
                                doublereal& tlow, doublereal& thigh,
                                doublereal& pref,

src/thermo/Nasa9PolyMultiTempRegion.cpp

@@ -127,6 +127,11 @@ void Nasa9PolyMultiTempRegion::updatePropertiesTemp(const doublereal temp,
     m_regionPts[m_currRegion]->updatePropertiesTemp(temp, cp_R, h_RT, s_R);
 }
 
+size_t Nasa9PolyMultiTempRegion::nCoeffs() const
+{
+    return 11*m_regionPts.size() + 1;
+}
+
 void Nasa9PolyMultiTempRegion::reportParameters(size_t& n, int& type,
         doublereal& tlow, doublereal& thigh,
         doublereal& pref,

src/thermo/SpeciesThermoInterpType.cpp

@@ -41,6 +41,12 @@ void SpeciesThermoInterpType::updatePropertiesTemp(const double temp,
                        "Not implemented");
 }
 
+size_t SpeciesThermoInterpType::nCoeffs() const
+{
+    throw CanteraError("SpeciesThermoInterpType::nCoeffs",
+                       "Not implemented");
+}
+
 void SpeciesThermoInterpType::reportParameters(size_t& index, int& type,
         double& minTemp, double& maxTemp, double& refPressure,
         double* const coeffs) const