Function custom_reduce

ciphercore-base/src/ops/utils.rs:349–356

Reduces an array over the first dimension, using log number of `combine` calls. `combine` receives two arrays (first, second) of same shape, and needs to return one array of same shape. `combine` is assumed to be associative and commutative.

(node: Node, combine: impl Fn(Node, Node) -> Result<Node>)

/// `combine` receives two arrays (first, second) of same shape, and needs to return one array of
/// same shape. `combine` is assumed to be associative and commutative.
pub fn custom_reduce(node: Node, combine: impl Fn(Node, Node) -> Result<Node>) -> Result<Node> {
    custom_reduce_vec(vec![node], |first, second| {
        Ok(vec![combine(first[0].clone(), second[0].clone())?])
    })?
    .into_iter()
    .next()
    .ok_or_else(|| runtime_error!("Internal error: custom_reduce_vec returned empty vec"))
}

/// Reduces a vector of arrays sharing the same first dimension, over the first dimension, using
/// log number of `combine` calls.