270 lines
7.4 KiB
OCaml
270 lines
7.4 KiB
OCaml
[@@@warning "-27-50"]
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let todo = assert false
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(* Little OCaml reminder: *)
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type t = { a : int; b : int; c : int }
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let () =
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let x = { a = 0; b = 1; c = 2 } in
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let y = { x with a = 2 } in
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assert (y = { a = 2; b = 1; c = 2 })
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(** Discrete-time node *)
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type ('i, 'o, 'r) dnode =
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DNode : {
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state : 's; (** current state *)
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step : 's -> 'i -> 's * 'o; (** step function *)
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reset : 's -> 'r -> 's; (** reset function *)
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} -> ('i, 'o, 'r) dnode
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(** Run a discrete node on a list of inputs *)
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let drun (DNode n : ('i, 'o, 'r) dnode) (i : 'i list) : 'o list =
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todo
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type time =
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float (** [≥ 0.0] *)
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(** Interval-defined functions *)
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type 'a dense =
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{ h : time; (** horizon *)
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f : time -> 'a } (** [f : [0, h] -> α] *)
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(** Continuous-time signal *)
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type 'a signal =
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'a dense option
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(** Initial value problem (IVP) *)
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type ('y, 'yder) ivp =
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{ y0 : 'y; (** initial position *)
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fder : time -> 'y -> 'yder; (** derivative function on [[0.0, h]] *)
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h : time; } (** maximal horizon *)
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(** ODE solver *)
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type ('y, 'yder) csolver =
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(time, (** requested horizon *)
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'y dense, (** solution approximation *)
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('y, 'yder) ivp) (** initial value problem *)
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dnode
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(** Zero-crossing problem (ZCP) *)
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type ('y, 'zin) zcp =
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{ y0 : 'y; (** initial position *)
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fzer : time -> 'y -> 'zin; (** zero-crossing function *)
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h : time; } (** maximal horizon *)
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(** Zero-crossing solver *)
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type ('y, 'zin, 'zout) zsolver =
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('y dense, (** input value *)
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time * 'zout, (** horizon and zero-crossing events *)
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('y, 'zin) zcp) (** zero-crossing problem *)
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dnode
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(** Full solver (composition of an ODE and zero-crossing solver) *)
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type ('y, 'yder, 'zin, 'zout) solver =
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(time, (** requested horizon *)
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'y dense * 'zout, (** output and zero-crossing events *)
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('y, 'yder) ivp * ('y, 'zin) zcp) (** (re)initialization parameters *)
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dnode
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(** Compose an ODE solver and a zero-crossing solver *)
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let build_solver : ('y, 'yder) csolver ->
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('y, 'zin, 'zout) zsolver ->
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('y, 'yder, 'zin, 'zout) solver
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= fun (DNode cs) (DNode zs) ->
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let state = (cs.state, zs.state) in
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let step (cstate, zstate) (h : time) =
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todo in
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let reset (cstate, zstate) (ivp, zcp) =
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(cs.reset cstate ivp, zs.reset zstate zcp) in
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DNode { state; step; reset }
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(** Hybrid (discrete-time and continuous-time) node *)
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type ('i, 'o, 'r, 'y, 'yder, 'zin, 'zout) hnode =
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HNode : {
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state : 's; (** current state *)
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step : 's -> 'i -> 's * 'o; (** discrete step function *)
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reset : 's -> 'r -> 's; (** reset function *)
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fder : 's -> 'i -> 'y -> 'yder; (** derivative function *)
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fzer : 's -> 'i -> 'y -> 'zin; (** zero-crossing function *)
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fout : 's -> 'i -> 'y -> 'o; (** continuous output function *)
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cget : 's -> 'y; (** continuous state getter *)
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cset : 's -> 'y -> 's; (** continuous state setter *)
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zset : 's -> 'zout -> 's; (** zero-crossing information setter *)
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jump : 's -> bool; (** discrete go-again indicator *)
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} -> ('i, 'o, 'r, 'y, 'yder, 'zin, 'zout) hnode
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(** Simulation mode (either discrete or continuous) *)
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type mode = D | C
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(** Simulation state *)
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type ('i, 'o, 'r, 'y) state =
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State : {
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solver : (** solver state *)
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('y, 'yder, 'zin, 'zout) solver;
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model : (** model state *)
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('i, 'o, 'r, 'y, 'yder, 'zin, 'zout) hnode;
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input : 'i signal; (** current input *)
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time : time; (** current time *)
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mode : mode; (** current step mode *)
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} -> ('i, 'o, 'r, 'y) state
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(** Discrete simulation step *)
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let dstep (State ({ model = HNode m; solver = DNode s; _ } as state)) =
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let i = Option.get state.input in
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let (ms, o) = m.step m.state (todo (* current input? *)) in
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let model = HNode { m with state = todo (* ? *) } in
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let state =
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if m.jump ms then State { state with model = todo (* ? *) }
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else if state.time >= i.h then
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State { state with input = todo (* ? *); model; time = todo (* ? *) }
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else
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let y0 = todo (* ? *) and h = i.h -. state.time in
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let ivp = { h; y0; fder = fun t y -> m.fder ms (i.f todo (* ? *)) y } in
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let zcp = { h; y0; fzer = fun t y -> m.fzer ms (i.f todo (* ? *)) y } in
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let solver = DNode { s with state = s.reset s.state (ivp, zcp) } in
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State { state with model; solver; mode = todo (* ? *) } in
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(state, Some { h = 0.; f = fun _ -> o })
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(** Continuous simulation step *)
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let cstep (State ({ model = HNode m; solver = DNode s; _ } as st)) =
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let i = Option.get st.input in
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let (ss, (y, z)) = s.step s.state todo (* ? *) in
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let ms = m.zset (m.cset m.state (y.f y.h)) z in
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let out = Some { y with f = fun t -> m.fout ms todo (* ? *) (y.f t) } in
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let mode = if m.jump ms || st.time +. y.h >= i.h then D else C in
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let model = HNode { m with state = ms } in
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let solver = DNode { s with state = ss } in
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(State { st with model; solver; mode; time = todo (* ? *) }, out)
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(** Simulate a hybrid model with a solver *)
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let hsim : ('i, 'o, 'r, 'y, 'yder, 'zin, 'zout) hnode ->
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('y, 'yder, 'zin, 'zout) solver ->
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('i signal, 'o signal, 'r) dnode
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= fun model solver ->
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let state = State { model; solver; input = None; time = 0.; mode = D } in
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let step (State s as st) input = match (input, s.input, s.mode) with
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| Some _, None, _ -> dstep (State { s with input; time = 0.; mode = D })
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| None, Some _, D -> dstep st
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| None, Some _, C -> cstep st
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| None, None, _ -> (st, None)
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| Some _, Some _, _ -> invalid_arg "Not done processing previous input" in
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let reset (State ({ model = HNode m; _ } as s)) r =
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let model = HNode { m with state = m.reset m.state r } in
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State { s with model; input = None; time = 0.; mode = D } in
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DNode { state; step; reset }
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(** Run a simulation on a list of inputs *)
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let hrun (model : ('i, 'o, 'r, 'y, 'yder, 'zin, 'zout) hnode)
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(solver : ('y, 'yder, 'zin, 'zout) solver)
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(i : 'i dense list) : 'o dense list
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= let sim = hsim model solver and i = List.map Option.some i in
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let rec step os (DNode sim) i =
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let state, o = sim.step sim.state i in
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let sim = DNode { sim with state } in
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if o = None then (sim, List.rev_map Option.get os)
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else step (o :: os) sim None in
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List.fold_left_map (step []) sim i |> snd |> List.flatten
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