Why is Lua treating tables as numbers? - lua

Question

I was playing around with Lua and neural networks, and I stumbled across a weird bug in my code, where Lua appears to be treating a table as a number. I have the following code...
function CreateEmptyNeuron()
local neuron = {
val = 0,
forward = { },
backward = { },
}
return neuron;
end
--layerSize is an integer representing the size of the layer we're creating.
function CreateLayer(layerSize)
local layer = {}
for i = 1, layerSize, 1 do
local n = CreateEmptyNeuron();
table.insert(layer, n)
end
return layer;
end
--layerSize is actually an array of integers representing the array sizes of
--each individual layer (first layer is the input layer, last layer is output layer)
function CreateLayers(numLayers, layerSize)
local layers = {}
for i = 1, numLayers, 1 do
local layer = CreateLayer(layerSize[i]);
table.insert(layers, layer)
end
return layers;
end
--This function initializes the "val" variable in each table, and
--forward connects each neuron to every node in the next layer...
function ForwardConnectLayers(network)
for i = 1, #network, 1 do
local layer = network[i]
local next_layer = nil
if (i+1) < #network then
next_layer = network[i+1]
else
print("We have reached the output layer...")
next_layer = nil
end
for j = 1, #layer, 1 do
local neuron = layer[j]
neuron.val = (math.random() + math.random(0, 100))/100;
if next_layer ~= nil then
for x = 1, #next_layer, 1 do
neuron.forward[x] = math.random(1, 100)/100
print("Found forward layer...")
end
else
print("We cannot forward connect the output layer...\n")
end
end
end
end
function BackwardConnectLayers(network)
for i = 1, #network, 1 do
local layer = network[i]
local prev_layer = nil
if (i-1) > 1 then
prev_layer = network[i-1]
else
print("We have reached the input layer...")
prev_layer = nil
end
for j = #layer, 1, -1 do
local neuron = layer[j]
--neuron.val = (math.random() + math.random(0, 100))/100;
if prev_layer ~= nil then
for x = 1, #prev_layer, 1 do
table.insert(neuron.backward, prev_layer[x])
print("Found input layer...")
end
else
print("We cannot backward connect the input layer...\n")
end
end
end
end
function CreateBrain()
local LAYER_SIZES = {
10, 20, 20, 5
}
local brain = CreateLayers(4, LAYER_SIZES)
ForwardConnectLayers(brain)
BackwardConnectLayers(brain)
return brain;
end
AI = CreateBrain();
AI.Run = function(inputs, expectedOutputs)
local input_layer = AI[1]
local output_layer = AI[#AI]
for i = 0, #inputs, 1 do
input_layer[i] = inputs[i]
end
--For each layer in the network...
for l = 1, #AI, 1 do
--Get the next layer and this layer...
local this_layer = AI[l]
local next_layer = AI[l+1]
--And for each neuron in the next layer...
--Multiply the value of the neuron in this layer by
--the value of the modifier, and set the value of the next
--Neuron to be nextneuron.val + sum(<x>.val*<x>[k])
if next_layer ~= nil then
for m = 1, #next_layer, 1 do
local prev_layer_sum = 0
for n = 1, #this_layer, 1 do
local neuron = this_layer[n]
print(neuron)
end
end
end
end
end
ai_inputs = { 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 }
expected_outputs = { 8, 8, 8, 8, 8 }
AI.Run(ai_inputs, expected_outputs)
When I run the code as shown, it, as expected, prints a list of addresses to memory for Lua tables:
But then, if I alter AI.Run to the following:
AI.Run = function(inputs, expectedOutputs)
local input_layer = AI[1]
local output_layer = AI[#AI]
for i = 0, #inputs, 1 do
input_layer[i] = inputs[i]
end
--For each layer in the network...
for l = 1, #AI, 1 do
--Get the next layer and this layer...
local this_layer = AI[l]
local next_layer = AI[l+1]
--And for each neuron in the next layer...
--Multiply the value of the neuron in this layer by
--the value of the modifier, and set the value of the next
--Neuron to be nextneuron.val + sum(<x>.val*<x>[k])
if next_layer ~= nil then
for m = 1, #next_layer, 1 do
local prev_layer_sum = 0
for n = 1, #this_layer, 1 do
local neuron = this_layer[n]
for k, v in pairs(neuron) do
print(k .. ", " .. v)
end
end
end
end
end
end
I get the following error message:
Indicating that Lua thinks the table is a number... which is, suffice to say, confusing. There's probably some language technicality defining this behavior, but I can't find good documentation surrounding this (in part because I don't even know what term to search; I'm not usually a Lua programmer).
EDIT:
So, it appears, somewhere in the code, numbers are getting inserted into the layers...
(Link to online Lua compiler where you can run the code: http://tpcg.io/_WPRPQV)

Answer 1

Your AI.Run function does
local input_layer = AI[1]
for i = 0, #inputs, 1 do
input_layer[i] = inputs[i]
end
where inputs is a table of numbers, i.e. the first layer of your network is replaced by just numbers.
You probably want to replace the val of the neuron in that layer instead:
local input_layer = AI[1]
for i = 0, #inputs, 1 do
input_layer[i].val = inputs[i]
end