Function onehot

ciphercore-base/src/ops/utils.rs:329–344

One-hot encoding Inputs: val: val is the value to be encoded. It has shape [arbitrary_shape, N] Where N is the number of bits after A2B. max_val: max_val is the maximum value that can be encoded. max_val indicates the number of bits in the output. The output will have shape [arbitrary_shape, max_val]. Obviously, max_val must be less than 2^N. ids: ids is the precomputed array of values in the rang

(val: Node, max_val: usize, ids: Node)

//  let ids = ones.cum_sum(0)?.subtract(ones)?.a2b()?;
//  ```
pub fn onehot(val: Node, max_val: usize, ids: Node) -> Result<Node> {
    let ids = ids.get_slice(vec![SliceElement::SubArray(
        Some(0),
        Some(max_val as i64),
        None,
    )])?;
    let g = val.get_graph();
    // We need to calculate val == ids , but we need to compare bitwise
    // XOR(val_bits, Not(ids_bits)) is equivalent to val_bits == ids_bits
    // XOR is equivalent to addition modulo 2, and Not is equivalent to adding 1 modulo 2
    let bitwise_comparision = unsqueeze(val, -2)?.add(ids.add(constant_scalar(&g, 1, BIT)?)?)?;
    // val == ids only if bitwise_comparision is all ones
    // So we can reduce over the last dimension to get the result
    let res = reduce_mul(bitwise_comparision)?;
    Ok(res)
}

/// 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