[Transport] Make fitting errors accessible programmatically

include/cantera/transport/Transport.h

@@ -20,12 +20,12 @@
 
 #include "cantera/base/ct_defs.h"
 #include "cantera/base/ctexceptions.h"
+#include "cantera/base/AnyMap.h"
 
 namespace Cantera
 {
 
 class ThermoPhase;
-class AnyMap;
 
 /**
  * @addtogroup tranprops
@@ -389,6 +389,16 @@ class Transport
     //! separately.
     AnyMap parameters() const;
 
+    //! Get error metrics about any functional fits calculated for pure species
+    //! transport properties.
+    //!
+    //! See GasTransport::fitDiffCoeffs and GasTransport::fitProperties.
+    //!
+    //! @warning  This method is an experimental part of the %Cantera API and may be
+    //!      changed or removed without notice.
+    //! @since New in %Cantera 3.1.
+    AnyMap fittingErrors() const { return m_fittingErrors; };
+
     //! @name Transport manager construction
     //!
     //! These methods are used during construction.
@@ -421,6 +431,9 @@ class Transport
 
     //! Number of species
     size_t m_nsp = 0;
+
+    //! Maximum errors associated with fitting pure species transport properties.
+    AnyMap m_fittingErrors;
 };
 
 }

interfaces/cython/cantera/transport.pxd

@@ -18,7 +18,7 @@ cdef extern from "cantera/transport/Transport.h" namespace "Cantera":
         void getSpeciesViscosities(double*) except +translate_exception
         void getCollisionIntegralPolynomial(size_t i, size_t j, double* dataA, double* dataB, double* dataC) except +translate_exception
         void setCollisionIntegralPolynomial(size_t i, size_t j, double* dataA, double* dataB, double* dataC, cbool flag) except +translate_exception
-
+        CxxAnyMap fittingErrors()
 
 cdef extern from "cantera/transport/DustyGasTransport.h" namespace "Cantera":
     cdef cppclass CxxDustyGasTransport "Cantera::DustyGasTransport":

interfaces/cython/cantera/transport.pyx

@@ -393,6 +393,23 @@ cdef class Transport(_SolutionBase):
         self.transport.setCollisionIntegralPolynomial(i, j, &adata[0], &bdata[0],
                                                       &cdata[0], actualT)
 
+    property transport_fitting_errors:
+        """
+        Get error metrics about any functional fits calculated for pure species
+        transport properties. See {ct}`GasTransport::fitDiffCoeffs` and
+        {ct}`GasTransport::fitProperties`.
+
+        .. warning::
+
+            This property is an experimental part of the Cantera API and
+            may be changed or removed without notice.
+
+        .. versionadded:: 3.1
+        """
+        def __get__(self):
+            cdef CxxAnyMap stats = self.transport.fittingErrors()
+            return anymap_to_py(stats)
+
 cdef class DustyGasTransport(Transport):
     """
     Implements the "dusty gas" model for transport in porous media.

src/transport/GasTransport.cpp

@@ -616,6 +616,8 @@ void GasTransport::fitProperties(MMCollisionInt& integrals)
             mxerr = std::max(mxerr, fabs(err));
             mxrelerr = std::max(mxrelerr, fabs(relerr));
         }
+        m_fittingErrors["viscosity-max-abs-error"] = mxerr;
+        m_fittingErrors["viscosity-max-rel-error"] = mxrelerr;
 
         // evaluate max fit errors for conductivity
         for (size_t n = 0; n < np; n++) {
@@ -635,6 +637,8 @@ void GasTransport::fitProperties(MMCollisionInt& integrals)
         }
         m_visccoeffs.push_back(c);
         m_condcoeffs.push_back(c2);
+        m_fittingErrors["conductivity-max-abs-error"] = mxerr_cond;
+        m_fittingErrors["conductivity-max-rel-error"] = mxrelerr_cond;
 
         if (m_log_level >= 2) {
             writelog(m_thermo->speciesName(k) + ": [" + vec2str(c) + "]\n");
@@ -690,8 +694,7 @@ void GasTransport::fitDiffCoeffs(MMCollisionInt& integrals)
 
     // vector of polynomial coefficients
     vector<double> c(degree + 1), c2(degree + 1);
-    double err, relerr,
-               mxerr = 0.0, mxrelerr = 0.0;
+    double err, relerr, mxerr = 0.0, mxrelerr = 0.0;
 
     vector<double> diff(np + 1);
     m_diffcoeffs.clear();
@@ -744,6 +747,9 @@ void GasTransport::fitDiffCoeffs(MMCollisionInt& integrals)
             }
         }
     }
+
+    m_fittingErrors["diff-coeff-max-abs-error"] = mxerr;
+    m_fittingErrors["diff-coeff-max-rel-error"] = mxrelerr;
     if (m_log_level) {
         writelogf("Maximum binary diffusion coefficient absolute error:"
                  "  %12.6g\n", mxerr);

src/transport/IonGasTransport.cpp

@@ -235,6 +235,12 @@ void IonGasTransport::fitDiffCoeffs(MMCollisionInt& integrals)
             }
         }
     }
+    m_fittingErrors["diff-coeff-max-abs-error"] =
+        std::max(m_fittingErrors.getDouble("diff-coeff-max-abs-error", 0.0),
+                 mxerr);
+    m_fittingErrors["diff-coeff-max-rel-error"] =
+        std::max(m_fittingErrors.getDouble("diff-coeff-max-rel-error", 0.0),
+                 mxrelerr);
 
     if (m_log_level) {
         writelogf("Maximum binary diffusion coefficient absolute error:"

test/python/test_transport.py

@@ -71,13 +71,19 @@ def test_mixDiffCoeffsChange(self, phase):
 
     def test_CK_mode(self, phase):
         mu_ct = phase.viscosity
+        err_ct = phase.transport_fitting_errors
         phase.transport_model = 'mixture-averaged-CK'
         assert phase.transport_model == 'mixture-averaged-CK'
         mu_ck = phase.viscosity
+        err_ck = phase.transport_fitting_errors
         # values should be close, but not identical
         assert abs(mu_ct - mu_ck) / mu_ct > 1e-8
         assert abs(mu_ct - mu_ck) / mu_ct < 1e-2
 
+        # Cantera's fits should be an improvement in all cases
+        for key in err_ct:
+            assert err_ct[key] < err_ck[key]
+
     def test_ionGas(self, phase):
         # IonGasTransport gives the same result for a mixture
         # without ionized species