前端进度条性能优化、仿真结束后后处理优化；后端C代码生成流程优化：先识别来源，再按照已知未知量需求排序，最后局部求解

native/include/kernels.h

@@ -8,6 +8,13 @@ typedef struct {
 } 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;
+/* One entry per pipe branch, zero-initialized for each model_eval. Never shared
+ * across solver trials. Exact inputs, including medium constants, form the key. */
+typedef struct {
+    NativeMedium medium;
+    double p1, p2, T, diameter, length, roughness, flow;
+    int kind, valid;
+} NativePipeCache;
 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);
@@ -17,6 +24,9 @@ int native_medium_orifice(const NativeMedium *, double p1, double p2, double h1,
                           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);
+double native_pipe_flow_cached(NativePipeCache *, 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);