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use ndarray::{ArrayD, ArrayViewD};
use nodes::Operation;
#[derive(Debug, Serialize, Deserialize)]
pub enum Activation {
Relu { leak: f32 },
Sigmoid,
Tanh,
}
impl Operation for Activation {
fn eval(&self, inputs: &[ArrayViewD<f32>]) -> ArrayD<f32> {
assert_eq!(inputs.len(), 1, "Activation accepts one input");
match self {
Activation::Relu { leak } => inputs[0].mapv(|x| if x > 0.0 { x } else { x * leak }),
Activation::Sigmoid => inputs[0].mapv(sig),
Activation::Tanh => inputs[0].mapv(f32::tanh),
}
}
fn grad(&self, inputs: &[ArrayViewD<f32>], loss: ArrayViewD<f32>) -> Vec<ArrayD<f32>> {
assert_eq!(inputs.len(), 1, "Activation accepts one input");
let mut res = loss.to_owned();
match self {
Activation::Relu { leak } => {
res.zip_mut_with(&inputs[0], |l, i| {
if *i < 0.0 {
*l *= leak
}
});
}
Activation::Sigmoid => {
res.zip_mut_with(&inputs[0], |l, i| {
let s = sig(*i);
*l *= s * (1.0 - s);
});
}
Activation::Tanh => {
res.zip_mut_with(&inputs[0], |l, i| {
*l *= 1.0 - i.tanh().powi(2);
});
}
}
vec![res]
}
}
fn sig(x: f32) -> f32 {
1.0 / (1.0 + (-x).exp())
}