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type ('obs, 'act) transition = {
observation : 'obs;
action : 'act;
reward : float;
next_observation : 'obs;
terminated : bool;
truncated : bool;
}
type ('obs, 'act) step = {
observation : 'obs;
action : 'act;
reward : float;
terminated : bool;
value : float option;
log_prob : float option;
}
module Replay = struct
type ('obs, 'act) t = {
capacity : int;
mutable size : int;
mutable pos : int;
mutable observations : 'obs array;
mutable actions : 'act array;
rewards : float array;
mutable next_observations : 'obs array;
terminateds : bool array;
truncateds : bool array;
}
let create ~capacity =
if capacity <= 0 then
invalid_arg "Buffer.Replay.create: capacity must be positive";
{
capacity;
size = 0;
pos = 0;
observations = [||];
actions = [||];
rewards = Array.make capacity 0.0;
next_observations = [||];
terminateds = Array.make capacity false;
truncateds = Array.make capacity false;
}
let add buffer (transition : ('obs, 'act) transition) =
let needs_init = buffer.size = 0 in
if needs_init then (
buffer.observations <- Array.make buffer.capacity transition.observation;
buffer.actions <- Array.make buffer.capacity transition.action;
buffer.next_observations <-
Array.make buffer.capacity transition.next_observation);
buffer.observations.(buffer.pos) <- transition.observation;
buffer.actions.(buffer.pos) <- transition.action;
buffer.rewards.(buffer.pos) <- transition.reward;
buffer.next_observations.(buffer.pos) <- transition.next_observation;
buffer.terminateds.(buffer.pos) <- transition.terminated;
buffer.truncateds.(buffer.pos) <- transition.truncated;
buffer.pos <- (buffer.pos + 1) mod buffer.capacity;
buffer.size <- min (buffer.size + 1) buffer.capacity
let sample buffer ~rng ~batch_size =
if buffer.size = 0 then invalid_arg "Buffer.Replay.sample: buffer is empty";
if batch_size <= 0 then
invalid_arg "Buffer.Replay.sample: batch_size must be positive";
let actual_batch_size = min batch_size buffer.size in
let indices =
Rune.Rng.randint rng ~min:0 ~max:buffer.size [| actual_batch_size |]
in
let indices_arr : Int32.t array = Rune.to_array indices in
Array.init actual_batch_size (fun i ->
let idx = Int32.to_int indices_arr.(i) in
{
observation = buffer.observations.(idx);
action = buffer.actions.(idx);
reward = buffer.rewards.(idx);
next_observation = buffer.next_observations.(idx);
terminated = buffer.terminateds.(idx);
truncated = buffer.truncateds.(idx);
})
let size buffer = buffer.size
let is_full buffer = buffer.size = buffer.capacity
let clear buffer =
buffer.size <- 0;
buffer.pos <- 0
end
module Rollout = struct
type ('obs, 'act) step_with_advantage = {
step : ('obs, 'act) step;
mutable advantage : float option;
mutable return_ : float option;
}
type ('obs, 'act) t = {
capacity : int;
mutable size : int;
steps : ('obs, 'act) step_with_advantage array option ref;
}
let create ~capacity =
if capacity <= 0 then
invalid_arg "Buffer.Rollout.create: capacity must be positive";
{ capacity; size = 0; steps = ref None }
let add buffer step =
if buffer.size >= buffer.capacity then
invalid_arg "Buffer.Rollout.add: buffer is full";
match !(buffer.steps) with
| None ->
let arr =
Array.make buffer.capacity { step; advantage = None; return_ = None }
in
arr.(0) <- { step; advantage = None; return_ = None };
buffer.steps := Some arr;
buffer.size <- 1
| Some arr ->
arr.(buffer.size) <- { step; advantage = None; return_ = None };
buffer.size <- buffer.size + 1
let compute_advantages buffer ~last_value ~last_done ~gamma ~gae_lambda =
match !(buffer.steps) with
| None -> ()
| Some steps ->
if buffer.size = 0 then ()
else
let last_gae_lam = ref 0.0 in
for t = buffer.size - 1 downto 0 do
let step = steps.(t).step in
let value = Option.value step.value ~default:0.0 in
let next_value =
if t = buffer.size - 1 then if last_done then 0.0 else last_value
else Option.value steps.(t + 1).step.value ~default:0.0
in
let next_non_terminal =
if t = buffer.size - 1 then if last_done then 0.0 else 1.0
else if step.terminated then 0.0
else 1.0
in
let delta =
step.reward +. (gamma *. next_value *. next_non_terminal) -. value
in
last_gae_lam :=
delta
+. (gamma *. gae_lambda *. next_non_terminal *. !last_gae_lam);
steps.(t).advantage <- Some !last_gae_lam;
steps.(t).return_ <- Some (!last_gae_lam +. value)
done
let get buffer =
match !(buffer.steps) with
| None -> ([||], [||], [||])
| Some steps ->
let result_steps = Array.init buffer.size (fun i -> steps.(i).step) in
let advantages =
Array.init buffer.size (fun i ->
Option.value steps.(i).advantage ~default:0.0)
in
let returns =
Array.init buffer.size (fun i ->
Option.value steps.(i).return_ ~default:0.0)
in
buffer.steps := None;
buffer.size <- 0;
(result_steps, advantages, returns)
let size buffer = buffer.size
let is_full buffer = buffer.size = buffer.capacity
let clear buffer =
buffer.steps := None;
buffer.size <- 0
end