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core.cljc
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core.cljc
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(ns feedforward.core
(:require
[clojure.core.matrix :as clj-mtrx]))
(defn pow
"TODO: docstring"
[base exp]
#?(:cljs (js/Math.pow base exp)
:clj (.pow Math base exp)))
(defn sigmoid-activation-fn
"Return a real value in the range 0 to 1.
The reciprocal of one plus e to the negative `value`th power
`value` - a real valued number"
[value]
(/ 1 (+ 1 (pow 2.71828182846 (- value)))))
(defn z
"Return `z` = (wa+b) - vector of length p
`weights` - matrix of shape (p, m) of the form [[w11 w12 w13..][w21 w22 w23..][w31 w32 w33..]]
`activations` - vector of length m
`biases` - vector of length p"
[weights activations biases]
(clj-mtrx/add (clj-mtrx/inner-product weights activations) biases))
(defn feedforward-1
"Return a map with keys `:z` and `:a` where:
The value for :z is wa+b - vector of length m
The value for :a is σ(wa+b) - vector of length m
`weights` - matrix of shape (m, n)
`activations` - vector of length n
`biases` - vector of length m"
[weights activations biases]
(let [z-value (z weights activations biases)]
{:z z-value
:a (map sigmoid-activation-fn z-value)}))
(defn feedforward-n
"Return a seq of maps of the form returned by `feedforward-1`
`layers-seq` - seq of maps of the form returned by `gen-layer`
`activations` - vector with length equal to the second dim of the value for `:w` of the first item in layers-seq
`roll` - expects an empty vector, recursively accumulates the result"
[layers-seq activations roll]
(if (empty? layers-seq)
roll
(let [{:keys [w b]} (first layers-seq)
{:keys [z a] :as ff} (feedforward-1 w activations b)]
(feedforward-n (drop 1 layers-seq) a (conj roll ff)))))