diff --git a/main.lua b/main.lua
index 2db16be..db32810 100644
--- a/main.lua
+++ b/main.lua
@@ -145,13 +145,6 @@ local ror = bit.ror
 
 -- utilities.
 
-local function ifind(haystack, needle)
-    for i, v in ipairs(haystack) do
-        if v == needle then return i end
-    end
-    return nil
-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
@@ -569,13 +562,13 @@ local function fitness_shaping(rewards)
     local denom = 0
     for i, v in ipairs(rewards) do
         local l = log2(lamb / 2 + 1)
-        local r = log2(ifind(decreasing, v))
+        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(ifind(decreasing, v))
+        local r = log2(nn.indexof(decreasing, v))
         local numer = max(0, l - r)
         insert(shaped_returns, numer / denom + 1 / lamb)
     end
diff --git a/nn.lua b/nn.lua
index 996ef98..76d18b1 100644
--- a/nn.lua
+++ b/nn.lua
@@ -1,28 +1,36 @@
-local print = print
-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 exp = math.exp
 local insert = table.insert
-local remove = table.remove
+local ipairs = ipairs
+local log = math.log
+local max = math.max
+local min = math.min
 local open = io.open
-
-local bor = bit.bor
+local pairs = pairs
+local pi = math.pi
+local print = print
+local remove = table.remove
+local sin = math.sin
+local sqrt = math.sqrt
+local tostring = tostring
+local uniform = math.random
 
 local Base = require("Base")
 
-local function contains(t, a)
+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 indexof(t, a)
     assert(type(t) == "table")
-    for k, v in pairs(t) do if v == a then return true end end
-    return false
+    for k, v in pairs(t) do if v == a then return k end end
+    return nil
+end
+
+local function contains(t, a)
+    return indexof(t, a) ~= nil
 end
 
 local function prod(x, ...)
@@ -63,12 +71,6 @@ local function init_he_normal(t, fan_in, fan_out)
     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)
     out = out or {}
     local size = t
@@ -79,44 +81,50 @@ local function allocate(t, out, init)
     end
 end
 
-local function levelorder(field, node_in, nodes)
-    -- horribly inefficient.
+local function traverse(node_in, node_out, nodes, dummy_mode)
+    -- i have no idea if this is any algorithm in particular.
     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)
+    local seen_up = {}
+    local q = {node_out}
+    while #q > 0 do
+        local node = remove(q, 1)
+        seen_up[node] = true
+        for _, parent in ipairs(node.parents) do insert(q, parent) end
     end
-    for _, node in ipairs(down) do
-        seen[node] = bor(seen[node] or 0, 2)
-        if seen[node] == 3 then
-            insert(nodes, node)
+
+    if dummy_mode then seen_up[node_in] = true end
+
+    nodes = {}
+    q = {node_in}
+    while #q > 0 do
+        local node = remove(q, 1)
+        if seen_up[node] then
+            local all_parents_added = true
+            for _, parent in ipairs(node.parents) do
+                if not contains(nodes, parent) then
+                    all_parents_added = false
+                    break
+                end
+            end
+            if not contains(nodes, node) and all_parents_added then
+                insert(nodes, node)
+            end
+            for _, child in ipairs(node.children) do insert(q, child) end
         end
     end
+
+    if dummy_mode then remove(nodes, indexof(nodes, node_in)) end
+
     return nodes
 end
 
 local function traverse_all(nodes_in, nodes_out, nodes)
-    local all_in = {children={}}
-    local all_out = {parents={}}
+    local all_in  = {children={}, parents={}}
+    local all_out = {children={}, 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 {})
+    return traverse(all_in, all_out, nodes or {}, true)
 end
 
 local Weights = Base:extend()
@@ -443,14 +451,17 @@ function Model:load(fn)
 end
 
 return {
-    uniform = uniform,
-    normal = normal,
-
     copy = copy,
+    indexof = indexof,
+    contains = contains,
+    prod = prod,
+    normal = normal,
     zeros = zeros,
     init_zeros = init_zeros,
     init_he_uniform = init_he_uniform,
     init_he_normal = init_he_normal,
+    allocate = allocate,
+    traverse = traverse,
 
     Weights = Weights,
     Layer   = Layer,