commit 29f3c278eac06a39ccb8f957f193e8f06ef4d4ff
Author: Connor <cloningdonor@gmail.com>
Date:   Wed Jun 28 02:33:18 2017 -0700

diff --git a/main.lua b/main.lua
new file mode 100644
index 0000000..adf98f2
--- /dev/null
+++ b/main.lua
@@ -0,0 +1,561 @@
+-- be strict about globals.
+
+local mt = getmetatable(_G)
+if mt == nil then
+    mt = {}
+    setmetatable(_G, mt)
+end
+
+function mt.__newindex(t, n, v)
+    error("cannot assign undeclared global '" .. tostring(n) .. "'", 2)
+end
+
+function mt.__index(t, n)
+    error("cannot use undeclared global '" .. tostring(n) .. "'", 2)
+end
+
+local function globalize(t)
+    for k, v in pairs(t) do
+        rawset(_G, k, v)
+    end
+end
+
+-- localize some stuff.
+
+local ipairs = ipairs
+local pairs = pairs
+local select = select
+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 sqrt = math.sqrt
+local random = math.random
+local insert = table.insert
+local remove = table.remove
+local unpack = table.unpack or unpack
+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 function clamp(x, l, u) return min(max(x, l), u) 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 argmax2(t)
+    return t[1] > t[2]
+end
+
+-- game-agnostic stuff (i.e. the network itself)
+
+package.loaded['nn'] = nil -- DEBUG
+local nn = require("nn")
+
+local network
+local nn_x
+local nn_y
+local nn_z
+local function make_network(input_size, buttons)
+    nn_x = nn.Input(input_size)
+    nn_y = nn_x
+    nn_z = {}
+    nn_y = nn_y:feed(nn.Dense(input_size))
+    nn_y = nn_y:feed(nn.Relu())
+    --nn_y = nn_y:feed(nn.Dense(floor(input_size / 16)))
+    --nn_y = nn_y:feed(nn.Relu())
+    --nn_y = nn_y:feed(nn.Dense(floor(input_size / 16)))
+    --nn_y = nn_y:feed(nn.Relu())
+    for i = 1, buttons do
+        nn_z[i] = nn_y
+        nn_z[i] = nn_z[i]:feed(nn.Dense(2))
+        nn_z[i] = nn_z[i]:feed(nn.Softmax())
+    end
+
+    return nn.Model({nn_x}, nn_z)
+end
+
+-- and here we go with the game stuff.
+
+local enable_overlay = false
+local enable_network = true
+
+--[[
+https://gist.githubusercontent.com/1wErt3r/4048722/raw/59e88c0028a58c6d7b9156749230ccac647bc7d4/SMBDIS.ASM
+--]]
+
+local rotation_offsets = { -- FIXME: not all of these are pixel-perfect.
+    0, -40, -- 0
+    6, -38,
+    15, -37,
+    22, -32,
+    28, -28,
+    32, -22,
+    37, -14,
+    39, -6,
+    40, 0, -- 8
+    38, 7,
+    37, 15,
+    33, 23,
+    27, 29,
+    22, 33,
+    14, 37,
+    6, 39,
+    0, 41, -- 10
+    -7, 40,
+    -16, 38,
+    -22, 34,
+    -28, 28,
+    -34, 23,
+    -38, 16,
+    -40, 8,
+    -40, -0, -- 18
+    -40, -6,
+    -38, -14,
+    -34, -22,
+    -28, -28,
+    -22, -32,
+    -16, -36,
+    -8, -38,
+}
+
+local startsave = savestate.create(1)
+
+local poketime = false
+
+local sprite_input = {}
+local tile_input = {}
+
+local function shitsprite(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 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 shittile(x, y, t)
+    tile_input[#tile_input+1] = t
+    if t == 0 then return end
+    if 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 reward
+local powerup_old
+local status_old
+local coins_old
+
+local once = false
+local reset = true
+
+emu.poweron()
+emu.unpause()
+emu.speedmode("normal")
+
+local function opermode() return R(0x770) end
+local function paused() return band(R(0x776), 1) end
+local function subroutine() return R(0xE) end
+
+local function getstate()
+    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 ok_routines = {
+    [0x4] = true, -- sliding down flagpole
+    [0x5] = true, -- end of level auto-walk
+    [0x7] = true, -- start of level auto-walk
+    [0x8] = true, -- normal (in control)
+    [0x9] = true, -- acquiring mushroom
+    [0xA] = true, -- losing big mario
+    [0xB] = true, -- uhh
+    [0xC] = true, -- acquiring fireflower
+}
+
+local fuckstates = {
+    power = true,
+    waiting_demo = true,
+    playing_demo = true,
+    unknown = true,
+    lose = true,
+    paused = true,
+}
+
+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 state_old = ''
+while false do
+    local state = getstate()
+    if state ~= state_old then
+        print(emu.framecount(), state)
+        state_old = state
+    end
+    advance()
+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 = rotation_offsets[rot*2+1], rotation_offsets[rot*2+2]
+            x, y = x + x_off, y + y_off
+        end
+        if invisible then
+            shitsprite(0, 0, 0)
+        else
+            shitsprite(x, y, tid + 1)
+        end
+    end
+end
+
+local function handle_fireballs()
+    -- 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
+            shitsprite(0, 0, 0)
+        else
+            shitsprite(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
+            shitsprite(0, 0, 0)
+        else
+            shitsprite(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
+            shitsprite(x, y, state + 1)
+        else
+            shitsprite(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
+            shitsprite(x, y, state + 1)
+        else
+            shitsprite(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
+    tile_input[#tile_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
+            shittile(sx, sy, t)
+        end
+    end
+end
+
+while true do
+    while fuckstates[getstate()] do
+        --gui.text(120, 124, ("%02X"):format(subroutine()), '#FFFFFF', '#0000003F')
+        -- mash the start button until we have control.
+        -- TODO: learn this too.
+        --local jp = joypad.read(1)
+        local jp = {
+            up = false,
+            down = false,
+            left = false,
+            right = false,
+            A = false,
+            B = false,
+            select = false,
+            start = emu.framecount() % 2 == 1,
+        }
+        joypad.write(1, jp)
+
+        reset = true
+
+        gui.text(4, 12, getstate(), '#FFFFFF', '#0000003F')
+        advance()
+
+        -- bit of a hack:
+        while getstate() == "loading" do advance() end
+        state_old = getstate()
+    end
+
+    if reset then
+        print("resetting in state:", getstate())
+
+        if once then
+            savestate.load(startsave)
+            print("end of trial reward:", reward)
+            print()
+        else
+            savestate.save(startsave)
+        end
+        once = true
+
+        -- bit of a hack:
+        if getstate() == 'loading' then advance() end
+        reward = 0
+        powerup_old = R(0x754)
+        status_old = R(0x756)
+        coins_old = R(0x7ED) * 10 + R(0x7EE)
+
+        -- set lives to 0. you only got one shot!
+        -- unless you get a 1-up, in which case, please continue!
+        W(0x75A, 0)
+
+        emu.frameadvance() -- prevents emulator from quirking up.
+
+        reset = false
+        if network ~= nil then network:reset() end -- FIXME: hack
+    end
+
+    if not enable_network then
+        -- infinite time cheat. super handy for testing.
+        if R(0xE) == 8 then
+            W(0x7F8, 9)
+            W(0x7F9, 9)
+            W(0x7FA, 10)
+            poketime = true
+        elseif poketime then
+            poketime = false
+            W(0x7F8, 0)
+            W(0x7F9, 0)
+            W(0x7FA, 1)
+        end
+
+        -- infinite lives.
+        W(0x75A, 1)
+    end
+
+    -- empty input lists without creating a new table.
+    for k, v in pairs(sprite_input) do sprite_input[k] = nil end
+    for k, v in pairs(tile_input) do tile_input[k] = nil end
+
+    -- player
+    -- TODO: add check if mario is playable.
+    local x, y = getxy(0, 0x86, 0xCE, 0x6D, 0xB5)
+    local powerup = R(0x754)
+    local status = R(0x756)
+    shitsprite(x + 8, y + 24, -powerup - 1)
+
+    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 screen_scroll_delta = R(0x775)
+    local flagpole_bonus = subroutine() == 4 and 1 or 0
+    local reward_delta = screen_scroll_delta + status_delta * 256 + flagpole_bonus
+
+    reward = reward + reward_delta
+
+    --gui.text(4, 12, ("%02X"):format(#sprite_input), '#FFFFFF', '#0000003F')
+    --gui.text(4, 22, ("%02X"):format(#tile_input), '#FFFFFF', '#0000003F')
+    gui.text(72, 12, ("%+4i"):format(reward_delta), '#FFFFFF', '#0000003F')
+    gui.text(112, 12, ("%+4i"):format(reward), '#FFFFFF', '#0000003F')
+
+    if getstate() == 'dead' and state_old ~= 'dead' then
+        print("dead. lives remaining:", R(0x75A, 0))
+        if R(0x75A, 0) == 0 then reset = true end
+    end
+    if getstate() == 'lose' then
+        print("ran out of lives.")
+        reset = true
+    end
+
+    -- every few frames mario stands still, forcibly decrease the timer.
+    local timer_loser = 1/5
+    if math.random() > 1 - timer_loser and R(0x1D) == 0 and R(0x57) == 0 then
+        local timer = R(0x7F8) * 100 + R(0x7F9) * 10 + R(0x7FA)
+        timer = clamp(timer - 1, 0, 400)
+        W(0x7F8, floor(timer / 100))
+        W(0x7F9, floor((timer / 10) % 10))
+        W(0x7FA, floor(timer % 10))
+    end
+
+    local X = {} -- TODO: cache.
+    for i, v in ipairs(sprite_input) do insert(X, v / 256) end
+    for i, v in ipairs(tile_input) do insert(X, v / 256) end
+
+    if network == nil then
+        network = make_network(#X, 8); network:reset()
+        print("parameters:", network.n_param)
+    end
+
+    if enable_network and getstate() == 'playing' then
+        local outputs = network:forward(X)
+        local softmaxed = {
+            outputs[nn_z[1]],
+            outputs[nn_z[2]],
+            outputs[nn_z[3]],
+            outputs[nn_z[4]],
+            outputs[nn_z[5]],
+            outputs[nn_z[6]],
+            outputs[nn_z[7]],
+            outputs[nn_z[8]],
+        }
+        local jp = {
+            up      = argmax2(softmaxed[1]),
+            down    = argmax2(softmaxed[2]),
+            left    = argmax2(softmaxed[3]),
+            right   = argmax2(softmaxed[4]),
+            A       = argmax2(softmaxed[5]),
+            B       = argmax2(softmaxed[6]),
+            start   = argmax2(softmaxed[7]),
+            select  = argmax2(softmaxed[8]),
+        }
+        joypad.write(1, jp)
+    end
+
+    coins_old = coins
+    powerup_old = powerup
+    status_old = status
+    state_old = getstate()
+    advance()
+end
diff --git a/nn.lua b/nn.lua
new file mode 100644
index 0000000..26c5a49
--- /dev/null
+++ b/nn.lua
@@ -0,0 +1,377 @@
+local tostring = tostring
+local ipairs = ipairs
+local pairs = pairs
+local uniform = math.random
+local sqrt = math.sqrt
+local log = math.log
+local pi = math.pi
+local exp = math.exp
+local min = math.min
+local max = math.max
+local cos = math.cos
+local sin = math.sin
+local insert = table.insert
+local remove = table.remove
+
+local bor = bit.bor
+
+local Base = require("Base")
+
+local function contains(t, a)
+    assert(type(t) == "table")
+    for k, v in pairs(t) do if v == a then return true end end
+    return false
+end
+
+local function normal()
+    return sqrt(-2 * log(uniform() + 1e-8) + 1e-8) * cos(2 * pi * uniform()) / 2
+end
+
+local function zeros(n, out)
+    local out = out or {}
+    for i = 1, n do out[i] = 0 end
+    return out
+end
+
+local function init_zeros(t, fan_in, fan_out)
+    for i = 1, #t do t[i] = 0 end
+    return t
+end
+
+local function init_he_uniform(t, fan_in, fan_out)
+    local s = sqrt(6 / fan_in)
+    for i = 1, #t do t[i] = (uniform() * 2 - 1) * s end
+    return t
+end
+
+local function init_he_normal(t, fan_in, fan_out)
+    local s = sqrt(2 / fan_in)
+    for i = 1, #t do t[i] = normal() * s end
+    return t
+end
+
+local function copy(t) -- shallow copy
+    local new_t = {}
+    for k, v in pairs(t) do new_t[k] = v end
+    return new_t
+end
+
+local function allocate(t, out, init)
+    -- FIXME: this code is fucking disgusting.
+
+    out = out or {}
+    assert(type(out) == "table", type(out))
+    if type(t) == "number" then
+        local size = t
+        if init ~= nil then
+            return init(zeros(size, out))
+        else
+            return zeros(size, out)
+        end
+    end
+    local topsize = t[1]
+    t = copy(t)
+    remove(t, 1)
+    if #t == 1 then t = t[1] end
+    for i = 1, topsize do
+        local res = allocate(t, nil, init)
+        assert(res ~= nil)
+        insert(out, res)
+    end
+    return out
+end
+
+local Weights = Base:extend()
+local Layer = Base:extend()
+local Model = Base:extend()
+local Input = Layer:extend()
+local Relu = Layer:extend()
+local Dense = Layer:extend()
+local Softmax = Layer:extend()
+
+function Weights:init(weight_init)
+    self.weight_init = weight_init
+end
+
+function Weights:allocate(fan_in, fan_out)
+    return allocate(self.size, self, function(t)
+        --print('initializing weights of size', self.size, 'with fans', fan_in, fan_out)
+        return self.weight_init(t, fan_in, fan_out)
+    end)
+end
+
+--[[
+local w = Weights(init_he_uniform)
+w.size = {16, 16}
+w:allocate(16, 16)
+print(w)
+do return end
+
+local w = zeros(16)
+for i = 1, #w do w[i] = normal() * 1920 / 2560 end
+print(w)
+--]]
+
+local counter = {}
+function Layer:init(name)
+    assert(type(name) == "string")
+    counter[name] = (counter[name] or 0) + 1
+    self.name = name.."["..tostring(counter[name]).."]"
+    self.parents = {}
+    self.children = {}
+    self.weights = {}
+    --self.size_in = nil
+    --self.size_out = nil
+end
+
+function Layer:make_shape(parent)
+    if self.size_in == nil then self.size_in = parent.size_out end
+    if self.size_out == nil then self.size_out = self.size_in end
+end
+
+function Layer:feed(child)
+    assert(self.size_out ~= nil)
+    child:make_shape(self)
+    insert(self.children, child)
+    insert(child.parents, self)
+    return child
+end
+
+function Layer:forward()
+    error("Unimplemented.")
+end
+
+function Layer:forward_deterministic(...)
+    return self:forward(...)
+end
+
+function Layer:_new_weights(init)
+    local w = Weights(init)
+    insert(self.weights, w)
+    return w
+end
+
+local function prod(x, ...)
+    if type(x) == "table" then
+        return prod(unpack(x))
+    end
+    local ret = x
+    for i = 1, select("#", ...) do
+        ret = ret * select(i, ...)
+    end
+    return ret
+end
+
+function Layer:getsize()
+    local size = 0
+    for i, w in ipairs(self.weights) do size = size + prod(w.size) end
+    return size
+end
+
+function Layer:init_weights()
+    for i, w in ipairs(self.weights) do
+        --print("allocating weights", i, "of", self.name)
+        for j, v in ipairs(w) do w[j] = nil end -- FIXME: HACK
+        w:allocate(self.size_in, self.size_out)
+    end
+end
+
+function Layer:_propagate(edges, deterministic)
+    assert(#edges == 1, #edges) -- override this if you need multiple parents.
+    if deterministic then
+        return self:forward_deterministic(edges[1])
+    else
+        return self:forward(edges[1])
+    end
+end
+
+function Layer:propagate(values, deterministic)
+    local edges = {}
+    for i, parent in ipairs(self.parents) do
+        if values[parent] ~= nil then
+            local X = values[parent]
+            insert(edges, X)
+        end
+    end
+    assert(#edges > 0, #edges)
+    local Y = self:_propagate(edges, deterministic)
+    return Y
+end
+
+function Input:init(size)
+    Layer.init(self, "Input")
+    assert(type(size) == 'number')
+    self.size_in = size
+    self.size_out = size
+end
+
+function Input:forward(X)
+    assert(#X == self.size_in)
+    return X
+end
+
+function Relu:init()
+    Layer.init(self, "Relu")
+end
+
+function Relu:forward(X)
+    assert(#X == self.size_in)
+    self.cache = self.cache or zeros(self.size_out)
+    local Y = self.cache
+
+    for i = 1, #X do Y[i] = X[i] >= 0 and X[i] or 0 end
+
+    assert(#Y == self.size_out)
+    return Y
+end
+
+function Dense:init(dim)
+    Layer.init(self, "Dense")
+    assert(type(dim) == "number")
+    self.dim = dim
+    self.size_out = dim
+    self.coeffs = self:_new_weights(init_he_normal) -- should be normal, but...
+    self.biases = self:_new_weights(init_zeros)
+end
+
+function Dense:make_shape(parent)
+    self.size_in = parent.size_out
+    self.coeffs.size = {self.dim, self.size_in}
+    self.biases.size = self.dim
+end
+
+function Dense:forward(X)
+    assert(#X == self.size_in)
+    self.cache = self.cache or zeros(self.size_out)
+    local Y = self.cache
+
+    for i = 1, #self.coeffs do
+        local res = 0
+        local c = self.coeffs[i]
+        for j = 1, #X do
+            res = res + X[j] * c[j]
+        end
+        Y[i] = res + self.biases[i]
+    end
+
+    assert(#Y == self.size_out)
+    return Y
+end
+
+function Softmax:init()
+    Layer.init(self, "Softmax")
+end
+
+function Softmax:forward(X)
+    assert(#X == self.size_in)
+    self.cache = self.cache or zeros(self.size_out)
+    local Y = self.cache
+
+    local alpha = 0
+    local num = {} -- TODO: cache
+    local den = 0
+
+    for i = 1, #X do alpha = max(alpha, X[i]) end
+    for i = 1, #X do num[i] = exp(X[i] - alpha) end
+    for i = 1, #X do den = den + num[i] end
+    for i = 1, #X do Y[i] = num[i] / den end
+
+    assert(#Y == self.size_out)
+    return Y
+end
+
+local function levelorder(field, node_in, nodes)
+    -- horribly inefficient.
+    nodes = nodes or {}
+    local q = {node_in}
+    while #q > 0 do
+        local node = q[1]
+        remove(q, 1)
+        insert(nodes, node)
+        for _, child in ipairs(node[field]) do
+            q[#q+1] = child
+        end
+    end
+    return nodes
+end
+
+local function traverse(node_in, node_out, nodes)
+    nodes = nodes or {}
+    local down = levelorder('children', node_in, {})
+    local up   = levelorder('parents', node_out, {})
+    local seen = {}
+    for _, node in ipairs(up) do
+        seen[node] = bor(seen[node] or 0, 1)
+    end
+    for _, node in ipairs(down) do
+        seen[node] = bor(seen[node] or 0, 2)
+        if seen[node] == 3 then
+            insert(nodes, node)
+        end
+    end
+    return nodes
+end
+
+local function traverse_all(nodes_in, nodes_out, nodes)
+    local all_in = {children={}}
+    local all_out = {parents={}}
+    for _, node in ipairs(nodes_in)  do insert(all_in.children, node) end
+    for _, node in ipairs(nodes_out) do insert(all_out.parents, node) end
+    return traverse(all_in, all_out, nodes or {})
+end
+
+function Model:init(nodes_in, nodes_out)
+    assert(#nodes_in > 0, #nodes_in)
+    assert(#nodes_out > 0, #nodes_out)
+    --if #nodes_in == 0 and type(nodes_in) == "table" then nodes_in = {nodes_in} end
+    --if #nodes_out == 0 and type(nodes_out) == "table" then nodes_out = {nodes_out} end
+
+    self.nodes_in = nodes_in
+    self.nodes_out = nodes_out
+
+    -- find all the used (inbetween) nodes in the graph.
+    self.nodes = traverse_all(self.nodes_in, self.nodes_out)
+end
+
+function Model:reset()
+    self.n_param = 0
+    for _, node in ipairs(self.nodes) do
+        node:init_weights()
+        self.n_param = self.n_param + node:getsize()
+    end
+end
+
+function Model:forward(X)
+    local values = {}
+    local outputs = {}
+    for i, node in ipairs(self.nodes) do
+        --print(i, node.name)
+        if contains(self.nodes_in, node) then
+            values[node] = node:_propagate({X})
+        else
+            values[node] = node:propagate(values)
+        end
+        if contains(self.nodes_out, node) then
+            outputs[node] = values[node]
+        end
+    end
+    return outputs
+end
+
+return {
+    uniform = uniform,
+    normal = normal,
+
+    zeros = zeros,
+    init_zeros = init_zeros,
+    init_he_uniform = init_he_uniform,
+    init_he_normal = init_he_normal,
+
+    Weights = Weights,
+    Layer   = Layer,
+    Model   = Model,
+    Input   = Input,
+    Relu    = Relu,
+    Dense   = Dense,
+    Softmax = Softmax,
+}