Replace Python numerical kernels with native C execution

native/include/kernels.h

@@ -0,0 +1,37 @@
+#ifndef NATIVE_KERNELS_H
+#define NATIVE_KERNELS_H
+typedef struct { double p, T, rho, u, h; } NativeGas;
+typedef struct {
+    int velocity_index;
+    double lower, upper;
+    double lower_restitution, upper_restitution, lower_threshold, upper_threshold;
+} NativeStop;
+/* Constants are emitted per medium instance by the model compiler. */
+typedef struct { int real_helium; double R, cp, Tref, slope, mu, muT, S; } NativeMedium;
+int native_medium_init(const NativeMedium *, double p, double T, double V, int legacy_ideal_initial, double *mU);
+double native_density(const NativeMedium *, double p, double T);
+double native_temperature_ph(const NativeMedium *, double p, double h);
+double native_viscosity(const NativeMedium *, double T, int diagnostic);
+int native_medium_gas(const NativeMedium *, double m, double U, double V, NativeGas *);
+int native_medium_orifice(const NativeMedium *, double p1, double p2, double h1, double h2,
+                          double cq_area, double opening, double *q, double *cm, double *v);
+double native_pipe_flow(const NativeMedium *, double p1, double p2, double T,
+                        double diameter, double length, double roughness, int kind);
+void native_pipe_diagnostics(const NativeMedium *, double q, double p, double T,
+                             double diameter, double length, double roughness,
+                             int diagnostic, double *result);
+double native_limit_force(double penetration, double velocity, double stiffness,
+                          double damping, double depth, int signed_force);
+int native_gas_init(double p, double T, double volume, double *mU);
+int native_gas(double m, double U, double volume, NativeGas *gas);
+int native_orifice(double p1, double p2, double h1, double h2,
+                   double cq_area, double opening, double *flow,
+                   double *cm, double *velocity);
+double native_contact(double penetration, double velocity, double stiffness,
+                      double damping, double pdis, int signed_force);
+void native_stop_motion(double x, double v, double lower, double upper,
+                        double *acceleration, double *velocity);
+double native_signal(double t, double start, int stages, int cyclic, const double *data);
+double native_signal_break(double t, double end, double start, int stages,
+                           int cyclic, const double *data);
+#endif