in gad/src/arith.rs [189:206]
fn sub(&mut self, v0: &Value<D>, v1: &Value<D>) -> Result<Value<D>> {
let result = self.eval().sub(v0.data(), v1.data())?;
let value = self.make_node(result, vec![v0.input(), v1.input()], {
let id0 = v0.id();
let id1 = v1.id();
move |graph, store, gradient| {
if let Some(id) = id0 {
store.add_gradient(graph, id, &gradient)?;
}
if let Some(id) = id1 {
let n = graph.neg(&gradient);
store.add_gradient(graph, id, &n)?;
}
Ok(())
}
});
Ok(value)
}