smbot/main.lua

local globalize = require("strict")

-- configuration.

--randomseed(11)

local cfg = require("config")
local gcfg = require("gameconfig")

-- state.

local epoch_i = 0
local base_params
local trial_i = -1 -- NOTE: trial 0 is an unperturbed trial, if enabled.
local trial_neg = true
local trial_noise = {}
local trial_rewards = {}
local trials_remaining = 0
local mom1  -- first moments in AMSgrad.
local mom2  -- second moments in AMSgrad.
local mom2max  -- running element-wise maximum of mom2.

local trial_frames = 0
local total_frames = 0

local force_start = false
local force_start_old = false

local startsave = savestate.create(1)

local poketime = false
local max_time

local sprite_input = {}
local tile_input = {}
local extra_input = {}

local jp

local screen_scroll_delta
local reward
--local all_rewards = {}

local powerup_old
local status_old
local coins_old
local score_old

local once = false
local reset = true

local state_old = ''
local last_trial_state

-- localize some stuff.

local print = print
local ipairs = ipairs
local pairs = pairs
local select = select
local open = io.open
local abs = math.abs
local floor = math.floor
local ceil = math.ceil
local min = math.min
local max = math.max
local exp = math.exp
local pow = math.pow
local log = math.log
local sqrt = math.sqrt
local random = math.random
local randomseed = math.randomseed
local insert = table.insert
local remove = table.remove
local unpack = table.unpack or unpack
local sort = table.sort
local R = memory.readbyteunsigned
local S = memory.readbyte --signed
local W = memory.writebyte

local band = bit.band
local bor = bit.bor
local bxor = bit.bxor
local bnot = bit.bnot
local lshift = bit.lshift
local rshift = bit.rshift
local arshift = bit.arshift
local rol = bit.rol
local ror = bit.ror

local gui = gui

-- utilities.

local log_map = {
    epoch = 1,
    trial_mean = 2,
    trial_std = 3,
    delta_mean = 4,
    delta_std = 5,
    step_std = 6,
    adam_std = 7,
    weight_mean = 8,
    weight_std = 9,
    test_trial = 10,
}

local function log_csv(t)
    if cfg.log_fn == nil then return end
    local f = open(cfg.log_fn, 'a')
    if f == nil then error("Failed to open log file "..cfg.log_fn) end
    local values = {}
    for k, v in pairs(t) do
        local i = log_map[k]
        if i == nil then error("Unexpected log key "..tostring(k)) end
        values[i] = v
    end
    for k, i in pairs(log_map) do
        if values[i] == nil then error("Missing log key "..tostring(k)) end
    end
    for i, v in ipairs(values) do
        f:write(tostring(v))
        if i ~= #values then f:write(",") end
    end
    f:write('\n')
    f:close()
end

local function boolean_xor(a, b)
    if a and b then return false end
    if not a and not b then return false end
    return true
end

local _invlog2 = 1 / log(2)
local function log2(x) return log(x) * _invlog2 end

local function clamp(x, l, u) return min(max(x, l), u) end

local function lerp(a, b, t) return a + (b - a) * clamp(t, 0, 1) end

local function argmax(...)
    local max_i = 0
    local max_v = -999999999
    for i=1, select("#", ...) do
        local v = select(i, ...)
        if v > max_v then
            max_i = i
            max_v = v
        end
    end
    return max_i
end

local function softchoice(...)
    local t = random()
    local psum = 0
    for i=1, select("#", ...) do
        local p = select(i, ...)
        psum = psum + p
        if t < psum then
            return i
        end
    end
end

local function argmax2(t)
    return t[1] > t[2]
end

local function rchoice2(t)
    return t[1] > random()
end

local function rbool()
    return 0.5 >= random()
end

local function empty(t)
    for k, _ in pairs(t) do t[k] = nil end
    return t
end

local function calc_mean_dev(x)
    local mean = 0
    for i, v in ipairs(x) do
        mean = mean + v / #x
    end

    local dev = 0
    for i, v in ipairs(x) do
        local delta = v - mean
        dev = dev + delta * delta / #x
    end

    return mean, sqrt(dev)
end

local function normalize(x, out)
    out = out or x
    local mean, dev = calc_mean_dev(x)
    if dev <= 0 then dev = 1 end
    for i, v in ipairs(x) do out[i] = (v - mean) / dev end
    return out
end

local function normalize_wrt(x, s, out)
    out = out or x
    local mean, dev = calc_mean_dev(s)
    if dev <= 0 then dev = 1 end
    for i, v in ipairs(x) do out[i] = (v - mean) / dev end
    return out
end

-- network parameters.

package.loaded['nn'] = nil -- DEBUG
local nn = require("nn")

local network
local nn_x, nn_tx, nn_ty, nn_y, nn_z
local function make_network(input_size)
    nn_x = nn.Input({input_size})
    nn_tx = nn.Input({gcfg.tile_count})
    nn_ty = nn_tx:feed(nn.Embed(256, 2))
    nn_y = nn.Merge()
    nn_x:feed(nn_y)
    nn_ty:feed(nn_y)

    nn_y = nn_y:feed(nn.Dense(128))
    if cfg.layernorm then nn_y = nn_y:feed(nn.LayerNorm()) end
    if cfg.deterministic then
        nn_y = nn_y:feed(nn.Relu())
    else
        nn_y = nn_y:feed(nn.Gelu())
    end

    nn_z = nn_y
    nn_z = nn_z:feed(nn.Dense(#gcfg.jp_lut))
    nn_z = nn_z:feed(nn.Softmax())
    return nn.Model({nn_x, nn_tx}, {nn_z})
end

-- and here we go with the game stuff.

-- disassembly used for reference:
-- https://gist.githubusercontent.com/1wErt3r/4048722/raw/59e88c0028a58c6d7b9156749230ccac647bc7d4/SMBDIS.ASM

local function get_timer()
    return R(0x7F8) * 100 + R(0x7F9) * 10 + R(0x7FA)
end

local function get_score()
    return R(0x7DE) * 10000 +
           R(0x7DF) * 1000 +
           R(0x7E0) * 100 +
           R(0x7E1) * 10 +
           R(0x7E2)
end

local function set_timer(time)
    W(0x7F8, floor(time / 100))
    W(0x7F9, floor((time / 10) % 10))
    W(0x7FA, floor(time % 10))
end

local function mark_sprite(x, y, t)
    if x < 0 or x >= 256 or y < 0 or y > 224 then
        sprite_input[#sprite_input+1] = 0
        sprite_input[#sprite_input+1] = 0
        sprite_input[#sprite_input+1] = 0
    else
        sprite_input[#sprite_input+1] = x
        sprite_input[#sprite_input+1] = y
        sprite_input[#sprite_input+1] = t
    end
    if t == 0 then return end
    if cfg.enable_overlay then
        gui.box(x-4, y-4, x+4, y+4)
        --gui.text(x-2, y-3, tostring(i), '#FFFFFF', '#00000000')
        gui.text(x-13, y-3-9, ("%+04i"):format(t), '#FFFFFF', '#0000003F')
        --gui.text(x-5, y-3+9, ("%02X"):format(x), '#FFFFFF', '#0000003F')
    end
end

local function mark_tile(x, y, t)
    tile_input[#tile_input+1] = t
    if t == 0 then return end
    if cfg.enable_overlay then
        gui.box(x-8, y-8, x+8, y+8)
        gui.text(x-5, y-3, ("%02X"):format(t), '#FFFFFF', '#00000000')
    end
end

local function getxy(i, x_addr, y_addr, pageloc_addr, hipos_addr)
    local spl_l = R(0x71A)
    local spl_r = R(0x71B)
    local sx_l = R(0x71C)
    local sx_r = R(0x71D)

    local x = R(x_addr + i)
    local y = R(y_addr + i)
    local sx, sy = x, y
    if pageloc_addr ~= nil then
        local page = R(pageloc_addr + i)
        sx = sx - sx_l - (spl_l - page) * 256
    else
        sx = sx - sx_l
    end
    if hipos_addr ~= nil then
        local hipos = S(hipos_addr + i)
        sy = sy + (hipos - 1) * 256
    end

    return sx, sy
end

local function paused() return band(R(0x776), 1) end

local function get_state()
    if R(0xE) == 0xFF then return 'power' end
    if R(0x774) > 0 then return 'lagging' end
    if R(0x7A2) > 0 then return 'waiting_demo' end
    if R(0x717) > 0 then return 'playing_demo' end
--  if R(0x770) == 0xFF then return 'power' end
    if paused() ~= 0 then return 'paused' end
    if R(0xE) == 0 then return 'world_screen' end
--  if R(0x712) == 1 then return 'deadmusic' end
    if R(0x7CA) == 0x94 then return 'dead' end
    if R(0xE) == 4 then return 'win_flagpole' end
    if R(0xE) == 5 then return 'win_walking' end
    if R(0xE) == 6 then return 'lose' end
--  if R(0x770) == 0 then return 'not_playing' end
    if R(0x770) == 2 then return 'win_castle' end
    if R(0x772) == 2 then return 'no_control' end
    if R(0x772) == 3 then return 'playing' end
    if R(0x770) == 1 then return 'loading' end
    if R(0x770) == 3 then return 'lose' end
    return 'unknown'
end

local function advance()
    emu.frameadvance()
    while emu.lagged() do emu.frameadvance() end -- skip lag frames.
    while R(0x774) > 0 do emu.frameadvance() end -- also lag frames.
end

local function handle_enemies()
    -- enemies, flagpole
    for i = 0, 5 do
        local x, y = getxy(i, 0x87, 0xCF, 0x6E, 0xB6)
        x, y = x + 8, y + 16
        local tid = R(0x16 + i)
        local flags = R(0xF + i)
        --local offscr = R(0x3D8 + i)
        local invisible = tid < 0x10 and flags == 0
        if tid == 0x30 then y = y - 8 end -- flagpole flag
        if tid == 0x31 then y = y - 8 end -- castle flag
        if tid == 0x16 then x, y = x - 4, y - 12 end -- fireworks
        if tid >= 0x24 and tid <= 0x29 then x, y = x + 16, y - 12 end -- moving platforms
        if tid == 0x2D then x, y = x, y end -- bowser (TODO: determine head or body)
        if tid == 0x15 then x, y = x, y - 12 end -- bowser fire
        if tid == 0x32 then x, y = x, y - 8 end -- spring
        -- tid == 0x35 -- toad
        if tid == 0x1D or tid == 0x1B then -- rotating fire bars
            x, y = x - 4, y - 12
            -- this is a mess... gotta find out its rotation and then project.
            -- TODO: handle long fire bars too
            local rot = R(0xA0 + i) --* 0x100 + R(0x58 + i)
            gui.text(x-13, y-3+9, ("%04X"):format(rot), '#FFFFFF', '#0000003F')
            local x_off, y_off = gcfg.rotation_offsets[rot*2+1], gcfg.rotation_offsets[rot*2+2]
            x, y = x + x_off, y + y_off
        end
        if invisible then
            mark_sprite(0, 0, 0)
        else
            mark_sprite(x, y, tid + 1)
        end
    end
end

local function handle_fireballs()
    for i = 0, 1 do
        local x, y = getxy(i, 0x8D, 0xD5, 0x74, 0xBC)
        x, y = x + 4, y + 4
        local state = R(0x24 + i)
        local invisible = state == 0
        if invisible then
            mark_sprite(0, 0, 0)
        else
            mark_sprite(x, y, 257)
        end
    end
end

local function handle_blocks()
    for i = 0, 3 do
        local x, y = getxy(i, 0x8F, 0xD7, 0x76, 0xBE)
        x, y = x + 8, y + 8
        local state = R(0x26 + i)
        local invisible = state == 0
        if invisible then
            mark_sprite(0, 0, 0)
        else
            mark_sprite(x, y, 258)
        end
    end
end

local function handle_hammers()
    -- hammers, coins, score bonus text...
    for i = 0, 8 do
        local x, y = getxy(i, 0x93, 0xDB, 0x7A, 0xC2)
        x, y = x + 8, y + 8
        local state = R(0x2A + i)
        -- skip coin effect states. not interactable; we don't care!
        if state ~= 0
        and state >= 0x30
        then
            mark_sprite(x, y, state + 1)
        else
            mark_sprite(0, 0, 0)
        end
    end
end

local function handle_misc()
    for i = 0, 0 do
        local x, y = getxy(i, 0x9C, 0xE4, 0x83, 0xCB)
        x, y = x + 8, y + 8
        local state = R(0x33 + i)
        if state ~= 0 then
            mark_sprite(x, y, state + 1)
        else
            mark_sprite(0, 0, 0)
        end
    end
end

local function handle_tiles()
    --local tile_col = R(0x6A0)
    local tile_scroll = floor(R(0x73F) / 16) + R(0x71A) * 16
    local tile_scroll_remainder = R(0x73F) % 16
    extra_input[#extra_input+1] = tile_scroll_remainder
    for y = 0, 12 do
        for x = 0, 16 do
            local col = (x + tile_scroll) % 32
            local t
            if col < 16 then
                t = R(0x500 + y * 16 + (col % 16))
            else
                t = R(0x5D0 + y * 16 + (col % 16))
            end
            local sx = x * 16 + 8 - tile_scroll_remainder
            local sy = y * 16 + 40
            mark_tile(sx, sy, t)
        end
    end
end

-- learning and evaluation.

local function prepare_epoch()
    base_params = network:collect()
    if cfg.playback_mode then return end

    print('preparing epoch '..tostring(epoch_i)..'.')
    empty(trial_noise)
    empty(trial_rewards)

    -- TODO: (optionally) save memory.
    --       generate noise as needed by saving the seed
    --       (the os.time() as of here) and calling nn.normal() each trial.
    -- of course this doubles the amount of time we spend generating noise,
    -- but that's a fair tradeoff for dividing memory used by noise by `epoch_trials`.

    local precision = (pow(cfg.deviation, 1/-0.51175585) - 8.68297257) / 1.66484392
    if cfg.graycode then
        print(("chosen precision: %.2f"):format(precision))
    end

    for i = 1, cfg.epoch_trials do
        local noise = nn.zeros(#base_params)
        -- NOTE: change in implementation: deviation is multiplied here
        --       and ONLY here now.
        if cfg.graycode then
            --local precision = 1 / cfg.deviation
            --print(cfg.deviation, precision)
            for j = 1, #base_params do
                noise[j] = exp(-precision * nn.uniform())
            end
            for j = 1, #base_params do
                noise[j] = nn.uniform() < 0.5 and noise[j] or -noise[j]
            end
            -- TODO? wrap/bound domain to [-1,1].
            --       dunno if this will work with the learning rate stuff.
        else
            for j = 1, #base_params do
                noise[j] = cfg.deviation * nn.normal()
            end
        end
        trial_noise[i] = noise
    end
    trial_i = -1
end

local function load_next_pair()
    trial_i = trial_i + 1
    if trial_i == 0 and not cfg.unperturbed_trial then
        trial_i = 1
        trial_neg = true
    end

    local W = nn.copy(base_params)

    if trial_i > 0 then
        if trial_neg then
            if not cfg.defer_prints then print('trial', trial_i, 'positive') end
            local noise = trial_noise[trial_i]
            for i, v in ipairs(base_params) do
                W[i] = v + noise[i]
            end

        else
            trial_i = trial_i - 1
            if not cfg.defer_prints then print('trial', trial_i, 'positive') end
            local noise = trial_noise[trial_i]
            for i, v in ipairs(base_params) do
                W[i] = v - noise[i]
            end
        end

        trial_neg = not trial_neg
    else
        if not cfg.defer_prints then print("test trial") end
    end

    network:distribute(W)
end

local function load_next_trial()
    if cfg.negate_trials then return load_next_pair() end
    trial_i = trial_i + 1
    local W = nn.copy(base_params)
    if trial_i == 0 and not cfg.unperturbed_trial then
        trial_i = 1
    end
    if trial_i > 0 then
        print('loading trial', trial_i)
        local noise = trial_noise[trial_i]
        for i, v in ipairs(base_params) do
            W[i] = v + noise[i]
        end
    else
        print("test trial")
    end
    network:distribute(W)
end

local function fitness_shaping(rewards)
    -- lifted from: https://github.com/atgambardella/pytorch-es/blob/master/train.py
    local decreasing = nn.copy(rewards)
    sort(decreasing, function(a, b) return a > b end)
    local shaped_returns = {}
    local lamb = #rewards

    local denom = 0
    for i, v in ipairs(rewards) do
        local l = log2(lamb / 2 + 1)
        local r = log2(nn.indexof(decreasing, v))
        denom = denom + max(0, l - r)
    end

    for i, v in ipairs(rewards) do
        local l = log2(lamb / 2 + 1)
        local r = log2(nn.indexof(decreasing, v))
        local numer = max(0, l - r)
        insert(shaped_returns, numer / denom + 1 / lamb)
    end

    return shaped_returns
end

local function unperturbed_rank(rewards, unperturbed_reward)
    -- lifted from: https://github.com/atgambardella/pytorch-es/blob/master/train.py
    local nth_place = 1
    for i, v in ipairs(rewards) do
        if v > unperturbed_reward then
            nth_place = nth_place +  1
        end
    end
    return nth_place
end

local function learn_from_epoch()
    print()
    --print('rewards:', trial_rewards)

    --for _, v in ipairs(trial_rewards) do insert(all_rewards, v) end

    local current_cost = trial_rewards[0] -- may be nil!

    if cfg.unperturbed_trial then
        local nth_place = unperturbed_rank(trial_rewards, current_cost)

        -- a rank of 1 means our gradient is uninformative.
        print(("test trial: %d out of %d"):format(nth_place, #trial_rewards))
    end

    local step = nn.zeros(#base_params)

    local delta_rewards -- only used for logging.
    local best_rewards
    if cfg.negate_trials then
        delta_rewards = {}
        for i = 1, cfg.epoch_trials do
            local ind = (i - 1) * 2 + 1
            local pos = trial_rewards[ind + 0]
            local neg = trial_rewards[ind + 1]
            delta_rewards[i] = abs(pos - neg)
        end

        -- select one (the best) reward of each pos/neg pair.
        best_rewards = {}
        for i = 1, cfg.epoch_trials do
            local ind = (i - 1) * 2 + 1
            local pos = trial_rewards[ind + 0]
            local neg = trial_rewards[ind + 1]
            best_rewards[i] = max(pos, neg)
        end
    else
        best_rewards = nn.copy(trial_rewards)
    end

    local indices = {}
    for i = 1, #best_rewards do indices[i] = i end
    sort(indices, function(a, b) return best_rewards[a] > best_rewards[b] end)

    --print("indices:", indices)
    for i = cfg.epoch_top_trials + 1, #best_rewards do indices[i] = nil end
    print("best trials:", indices)

    local top_rewards = {}
    for i = 1, #trial_rewards do top_rewards[i] = 0 end
    for _, ind in ipairs(indices) do
        local sind = (ind - 1) * 2 + 1
        top_rewards[sind + 0] = trial_rewards[sind + 0]
        top_rewards[sind + 1] = trial_rewards[sind + 1]
    end
    --print("top:", top_rewards)

    local top_delta_rewards = {} -- only used for printing.
    for i, ind in ipairs(indices) do
        local sind = (ind - 1) * 2 + 1
        top_delta_rewards[i] = abs(top_rewards[sind + 0] - top_rewards[sind + 1])
    end
    print("best deltas:", top_delta_rewards)

    if not cfg.ars_lips then
        local _, reward_dev = calc_mean_dev(top_rewards)
        --print("mean, dev:", _, reward_dev)
        if reward_dev == 0 then reward_dev = 1 end
        for i, v in ipairs(top_rewards) do top_rewards[i] = v / reward_dev end
    end

    -- NOTE: step no longer directly incorporates learning_rate.
    for i = 1, cfg.epoch_trials do
        local ind = (i - 1) * 2 + 1
        local pos = top_rewards[ind + 0]
        local neg = top_rewards[ind + 1]
        local reward = pos - neg
        if reward ~= 0 then
            local noise = trial_noise[i]

            if cfg.ars_lips then
                local _, dev = calc_mean_dev(noise)
                local c0 = neg - current_cost
                local c1 = pos - current_cost
                local l0 = abs(3 * c1 + c0)
                local l1 = abs(c1 + 3 * c0)
                local lips = max(l0, l1) / (2 * dev)
                --reward = pos / lips - neg / lips
                local old_reward = reward
                reward = reward / lips
                reward = reward / cfg.deviation -- FIXME: hack?
                --print(("trial %i reward: %.0f -> %.5f"):format(i, old_reward, reward))
            end

            for j, v in ipairs(noise) do
                step[j] = step[j] + reward * v / cfg.epoch_top_trials
            end
        end
    end

    local step_mean, step_dev = calc_mean_dev(step)
    print("step mean:", step_mean)
    print("step stddev:", step_dev)
    --print("full step stddev:", cfg.learning_rate * step_dev)

    local momstep_mean, momstep_dev = 0, 0
    if cfg.adamant then
        if mom1 == nil then mom1 = nn.zeros(#step) end
        if mom2 == nil then mom2 = nn.zeros(#step) end
        if mom2max == nil then mom2max = nn.zeros(#step) end

        local b1_t = pow(cfg.adam_b1, epoch_i)
        local b2_t = pow(cfg.adam_b2, epoch_i)

        -- NOTE: with LuaJIT, splitting this loop would
        --       almost certainly be faster.
        for i, v in ipairs(step) do
            mom1[i] = cfg.adam_b1 * mom1[i] + (1 - cfg.adam_b1) * v
            mom2[i] = cfg.adam_b2 * mom2[i] + (1 - cfg.adam_b2) * v * v
            mom2max[i] = max(mom2[i], mom2max[i])
            if cfg.adam_debias then
                local num = (mom1[i] / (1 - b1_t))
                local den = sqrt(mom2max[i] / (1 - b2_t)) + cfg.adam_eps
                step[i] = num / den
            else
                step[i] = mom1[i] / (sqrt(mom2max[i]) + cfg.adam_eps)
            end
        end

        momstep_mean, momstep_dev = calc_mean_dev(step)
        print("amsgrad mean:", momstep_mean)
        print("amsgrad stddev:", momstep_dev)
    end

    for i, v in ipairs(base_params) do
        base_params[i] = v + cfg.learning_rate * step[i] - cfg.weight_decay * v
    end

    local trial_mean, trial_std = calc_mean_dev(trial_rewards)
    local delta_mean, delta_std = calc_mean_dev(delta_rewards)
    local weight_mean, weight_std = calc_mean_dev(base_params)

    log_csv{
        epoch = epoch_i,
        trial_mean = trial_mean,
        trial_std = trial_std,
        delta_mean = delta_mean,
        delta_std = delta_std,
        step_std = step_dev,
        adam_std = momstep_dev,
        weight_mean = weight_mean,
        weight_std = weight_std,
        test_trial = current_cost or 0,
    }

    -- trying a heuristic...
    --[[
    if delta_std < trial_std then
        cfg.deviation = cfg.deviation * 0.933
        -- this one might be bad...
        cfg.weight_decay = cfg.weight_decay * 0.933
    end
    --]]

    if cfg.enable_network then
        network:distribute(base_params)
        network:save(cfg.params_fn)
    else
        print("note: not updating weights in playable mode.")
    end

    print()
end

local function joypad_mash(button)
    local jp_mash = {
        up = false,
        down = false,
        left = false,
        right = false,
        A = false,
        B = false,
        select = false,
        start = false,
    }
    assert(jp_mash[button] == false, "invalid button: "..tostring(button), 1)
    jp_mash[button] = emu.framecount() % 2 == 1
    joypad.write(1, jp_mash)
end

local function do_reset()
    local state = get_state()
    -- be a little more descriptive.
    if state == 'dead' and get_timer() == 0 then state = 'timeup' end

    if trial_i >= 0 and cfg.defer_prints then
        if trial_i == 0 then
            print('test trial reward:', reward, "("..state..")")
        elseif cfg.negate_trials then
            --local dir = trial_neg and "negative" or "positive"
            --print('trial', trial_i, dir, 'reward:', reward, "("..state..")")

            if trial_neg then
                local pos = trial_rewards[#trial_rewards]
                local neg = reward
                local fmt = "trial %i rewards: %+i, %+i (%s, %s)"
                print(fmt:format(trial_i, pos, neg, last_trial_state, state))
            end
            last_trial_state = state
        else
            print('trial', trial_i, 'reward:', reward, "("..state..")")
        end
    else
        print("reward:", reward, "("..state..")")
    end

    if trial_i >= 0 then
        if trial_i == 0 or not cfg.negate_trials then
            trial_rewards[trial_i] = reward
        else
            trial_rewards[#trial_rewards + 1] = reward
        end
    end

    if epoch_i == 0 or (trial_i == cfg.epoch_trials and trial_neg) then
        if epoch_i > 0 then learn_from_epoch() end
        if not cfg.playback_mode then epoch_i = epoch_i + 1 end
        prepare_epoch()
    end

    if get_state() == 'loading' then advance() end -- kind of a hack.
    reward = 0
    powerup_old = R(0x754)
    status_old = R(0x756)
    coins_old = R(0x7ED) * 10 + R(0x7EE)
    score_old = get_score()

    -- set number of lives. (mario gets n+1 chances)
    W(0x75A, cfg.starting_lives)

    if cfg.start_big then
        -- make mario "super".
        W(0x754, 0)
        W(0x756, 1)
    end

    --max_time = min(log(epoch_i) * 10 + 100, cfg.cap_time)
    --max_time = min(8 * sqrt(360 / cfg.epoch_trials * (epoch_i - 1)) + 100, cfg.cap_time)
    max_time = min(6 * sqrt(480 / cfg.epoch_trials * (epoch_i - 1)) + 60, cfg.cap_time)
    max_time = ceil(max_time)
    --max_time = cfg.cap_time

    if once then
        savestate.load(startsave)
    else
        savestate.save(startsave)
    end
    once = true

    jp = nil
    screen_scroll_delta = 0
    emu.frameadvance() -- prevents emulator from quirking up.

    load_next_trial()

    reset = false
end

local function init()
    network = make_network(gcfg.input_size)
    network:reset()
    network:print()
    print("parameters:", network.n_param)

    if cfg.init_zeros then
        local W = network:collect()
        for i, w in ipairs(W) do W[i] = 0 end
        network:distribute(W)
    end

    emu.poweron()
    emu.unpause()
    emu.speedmode("turbo")

    while emu.framecount() < 195 do  -- FIXME: don't hardcode this.
        joypad_mash('start')
        emu.frameadvance()
    end
    --print(emu.framecount())

    local res, err = pcall(network.load, network, cfg.params_fn)
    if res == false then print(err) end
end

local function prepare_reset()
    if cfg.playback_mode then return end
    reset = true
end

local function doit(dummy)
    local ingame_paused = get_state() == "paused"

    -- every few frames mario stands still, forcibly decrease the timer.
    -- this includes having the game paused.
    -- TODO: more robust. doesn't detect moonwalking against a wall.
    -- well, that shouldn't happen anymore now that i've disabled left+right.
    local timer = get_timer()
    if ingame_paused or random() > 1 - cfg.timer_loser and R(0x1D) == 0 and R(0x57) == 0 then
        timer = timer - 1
    end
    if not cfg.playback_mode then
        timer = clamp(timer, 0, max_time)
        if cfg.enable_network then
            set_timer(timer)
        end
    end

    local tf0 = total_frames % 1000
    local tf1 = (total_frames % 1000000 - tf0) / 1000
    local tf2 = (total_frames - tf0 - tf1) / 1000000
    gui.text(12, 212, ("%03i,%03i,%03i"):format(tf2,tf1,tf0), '#FFFFFF', '#0000003F')

    screen_scroll_delta = screen_scroll_delta + R(0x775)

    if dummy == true then
        -- don't invoke AI this frame. (keep holding the old inputs)
        gui.text(89, 16, ("%+5i"):format(reward), '#FFFFFF', '#0000003F')
        return
    end

    empty(sprite_input)
    empty(tile_input)
    empty(extra_input)

    -- TODO: check if mario is in a playable state.
    local x, y = getxy(0, 0x86, 0xCE, 0x6D, 0xB5)
    local powerup = R(0x754)
    local status = R(0x756)
    mark_sprite(x + 8, y + 24, -powerup - 1)

    local vx, vy = S(0x57), S(0x9F)
    insert(extra_input, vx)
    insert(extra_input, vy)

    if cfg.time_inputs then
        for i=2,5 do
            insert(extra_input, band(total_frames, lshift(1, i)))
        end
    end

    handle_enemies()
    handle_fireballs()
    -- blocks being hit. not interactable; we don't care!
    --handle_blocks()
    handle_hammers()
    handle_misc()
    handle_tiles()

    local coins = R(0x7ED) * 10 + R(0x7EE)
    local coins_delta = coins - coins_old
    -- handle wrap-around.
    if coins_delta < 0 then coins_delta = 100 + coins - coins_old end
    -- remember that 0 is big mario and 1 is small mario.
    local powerup_delta = powerup_old - powerup
    -- 2 is fire mario.
    local status_delta = clamp(status - status_old, -1, 1)
    local flagpole_bonus = R(0xE) == 4 and cfg.frameskip or 0
    --local reward_delta = screen_scroll_delta + status_delta * 256 + flagpole_bonus
    local score_delta = get_score() - score_old
    if score_delta < 0 then score_delta = 0 end
    local reward_delta = screen_scroll_delta + score_delta + flagpole_bonus
    screen_scroll_delta = 0

    if cfg.decrement_reward and reward_delta == 0 then reward_delta = reward_delta - 1 end

    if not ingame_paused then reward = reward + reward_delta end

    --gui.text(72, 12, ("%+4i"):format(reward_delta), '#FFFFFF', '#0000003F')
    gui.text(89, 16, ("%+5i"):format(reward), '#FFFFFF', '#0000003F')

    if get_state() == 'dead' and state_old ~= 'dead' then
        --print("dead. lives remaining:", R(0x75A, 0))
        if R(0x75A, 0) == 0 then prepare_reset() end
    end
    if get_state() == 'lose' then
        -- this shouldn't happen if we catch the deaths as above.
        print("ran out of lives.")
        if not cfg.playback_mode then prepare_reset() end
    end

    -- lose a point for every frame paused.
    --if ingame_paused then reward = reward - 1 end
    if ingame_paused then reward = reward - 402; prepare_reset() end

    -- if we've run out of time while the game is paused...
    -- that's cheating! unpause.
    force_start = ingame_paused and timer == 0

    local X = {}
    for i, v in ipairs(sprite_input) do insert(X, v / 256) end
    for i, v in ipairs(extra_input) do insert(X, v / 256) end
    nn.reshape(X, 1, gcfg.input_size)
    nn.reshape(tile_input, 1, gcfg.tile_count)

    if cfg.enable_network and get_state() == 'playing' or ingame_paused then
        total_frames = total_frames + cfg.frameskip

        local outputs = network:forward({[nn_x]=X, [nn_tx]=tile_input})

        local eps = lerp(cfg.eps_start, cfg.eps_stop, total_frames / cfg.eps_frames)
        if cfg.det_epsilon and random() < eps then
            local i = floor(random() * #gcfg.jp_lut) + 1
            jp = nn.copy(gcfg.jp_lut[i], jp)
        else
            local choose = cfg.deterministic and argmax or softchoice
            local ind = choose(unpack(outputs[nn_z]))
            jp = nn.copy(gcfg.jp_lut[ind], jp)
        end

        if force_start then
            jp = {
                up      = false,
                down    = false,
                left    = false,
                right   = false,
                A       = false,
                B       = false,
                start   = force_start_old,
                select  = false,
            }
        end
    end

    coins_old = coins
    powerup_old = powerup
    status_old = status
    force_start_old = force_start
    state_old = get_state()
    score_old = get_score()
end

init()

while true do
    gui.text(4, 12, get_state(), '#FFFFFF', '#0000003F')

    while gcfg.bad_states[get_state()] do
        -- mash the start button until we have control.
        joypad_mash('start')
        prepare_reset()

        advance()
        gui.text(4, 12, get_state(), '#FFFFFF', '#0000003F')

        while get_state() == "loading" do advance() end -- kind of a hack.
        state_old = get_state()
    end

    if reset then do_reset() end

    if not cfg.enable_network then
        -- infinite time cheat. super handy for testing.
        if R(0xE) == 8 then
            set_timer(667)
            poketime = true
        elseif poketime then
            poketime = false
            set_timer(1)
        end

        -- infinite lives.
        W(0x75A, 1)
    end

    -- FIXME: if the game lags then we might miss our frame to change inputs!
    --        don't rely on emu.framecount.
    local doot = jp == nil or emu.framecount() % cfg.frameskip == 0
    doit(not doot)

    -- jp might still be nil if we're not ingame or we're not playing.
    if jp ~= nil then joypad.write(1, jp) end

    advance()
end