refactor(poly/coeff): renamed coefficients to be more descriptive

src/poly/coeff/private/polyCoeff.cpp

@@ -4,20 +4,15 @@
 #include "polyCoeff.h"
 
 namespace polycoeff{
-  double xi_coeff_func(const mfem::Vector &x)
+  double nonlinearSourceCoeff(const mfem::Vector &x)
   {
-    return std::pow(x(0), 2);
+    // double r = x.Norml2();
+    return 1.0;
   }
 
-  void vec_xi_coeff_func(const mfem::Vector &x, mfem::Vector &v)
+  void diffusionCoeff(const mfem::Vector &x, mfem::Vector &v)
   {
-    v.SetSize(1);
-    v[0] = -std::pow(x(0), 2);
-  }
-
-  double theta_initial_guess(const mfem::Vector &x, double root)
-  {
-    double xi = x[0];
-    return 1 - std::pow(xi / root, 2);
+    v.SetSize(3);
+    for (int i = 0; i < 3; i++) { v(i) = -1; }
   }
 }