feat: a lot of stuff

src/lib/solvers/statefulRK45.ml

@@ -0,0 +1,69 @@
+
+open Hsim.Types
+open Hsim.Solver
+open Zls
+
+module Functional : Csolver.CsolverC =
+  struct
+    type ('state, 'vec) state = { state: 'state; vec: 'vec }
+    type session = Odexx.Ode45.t
+    type vec = carray
+
+    let csolve : ((session, vec) state, carray, carray) csolver_c =
+      let open Odexx.Ode45 in
+
+      let init _ =
+        let v = Zls.cmake 0 in
+        let state = initialize (fun _ _ _ -> ()) (vec v) in
+        set_stop_time state 1.0; { state; vec=v } in
+
+      let reset { fder; init; stop; _ } _ = 
+        let fder t cvec dvec = Zls.blit (fder t cvec) dvec in
+        let state = initialize fder (vec init) in
+        set_stop_time state stop;
+        { state; vec = init } in
+
+      let step ({ state ; vec=v } as s) h =
+        let y_nv = vec v in
+        let h = step state h y_nv in
+        let state = copy state in
+        let dky t = get_dky state y_nv t 0; unvec y_nv in
+        (h, dky), s in
+
+      let copy { state; vec } = { state; vec } in
+
+      DNodeC { init; step; reset; copy }
+  end
+
+module InPlace : Csolver.CsolverC =
+  struct
+    type ('state, 'vec) state = { mutable state: 'state; mutable vec : 'vec }
+    type session = Odexx.Ode45.t
+    type vec = carray
+
+    let csolve : ((session, vec) state, carray, carray) csolver_c =
+      let open Odexx.Ode45 in
+
+      let init _ =
+        let v = Zls.cmake 0 in
+        let state = initialize (fun _ _ _ -> ()) (vec v) in
+        set_stop_time state 1.0;
+        { state; vec=v } in
+
+      let reset { fder; init; stop; _ } s =
+        let fder t cvec dvec =
+          let dvec' = fder t cvec in Zls.blit dvec' dvec in
+        let state = initialize fder (vec init) in
+        set_stop_time state stop; s.state <- state ; s.vec <- init; s in
+
+      let step ({ state; vec=v } as s) h =
+        let y_nv = vec v in
+        let h = step state h y_nv in
+        let get_dky t = get_dky state y_nv t 0; unvec y_nv in
+        (h, get_dky), s in
+
+      let copy { state; vec } =
+        { state = copy state; vec = Zls.copy vec } in
+
+      DNodeC { init; reset; step; copy }
+  end