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use crate::ciphertext::RadixCiphertext;
use crate::ServerKey;
impl ServerKey {
/// Computes homomorphically the subtraction between ct_left and ct_right.
///
/// # Example
///
/// ```rust
/// use concrete_integer::gen_keys_radix;
/// use concrete_shortint::parameters::PARAM_MESSAGE_2_CARRY_2;
///
/// // We have 4 * 2 = 8 bits of message
/// let size = 4;
/// let (cks, sks) = gen_keys_radix(&PARAM_MESSAGE_2_CARRY_2, size);
///
/// let msg_1 = 120u8;
/// let msg_2 = 181u8;
///
/// // Encrypt two messages:
/// let mut ctxt_1 = cks.encrypt(msg_1 as u64);
/// let mut ctxt_2 = cks.encrypt(msg_2 as u64);
///
/// // Compute homomorphically a subtraction
/// let ct_res = sks.smart_sub_parallelized(&mut ctxt_1, &mut ctxt_2);
///
/// // Decrypt:
/// let res = cks.decrypt(&ct_res);
/// assert_eq!(msg_1.wrapping_sub(msg_2) as u64, res);
/// ```
pub fn smart_sub_parallelized(
&self,
ctxt_left: &mut RadixCiphertext,
ctxt_right: &mut RadixCiphertext,
) -> RadixCiphertext {
// If the ciphertext cannot be negated without exceeding the capacity of a ciphertext
if !self.is_neg_possible(ctxt_right) {
self.full_propagate_parallelized(ctxt_right);
}
// If the ciphertext cannot be added together without exceeding the capacity of a ciphertext
if !self.is_sub_possible(ctxt_left, ctxt_right) {
rayon::join(
|| self.full_propagate_parallelized(ctxt_left),
|| self.full_propagate_parallelized(ctxt_right),
);
}
let mut result = ctxt_left.clone();
self.unchecked_sub_assign(&mut result, ctxt_right);
result
}
/// Computes homomorphically the subtraction between ct_left and ct_right.
///
/// # Example
///
/// ```rust
/// use concrete_integer::gen_keys_radix;
/// use concrete_shortint::parameters::PARAM_MESSAGE_2_CARRY_2;
///
/// // We have 4 * 2 = 8 bits of message
/// let size = 4;
/// let (cks, sks) = gen_keys_radix(&PARAM_MESSAGE_2_CARRY_2, size);
///
/// let msg_1 = 120u8;
/// let msg_2 = 181u8;
///
/// // Encrypt two messages:
/// let mut ctxt_1 = cks.encrypt(msg_1 as u64);
/// let mut ctxt_2 = cks.encrypt(msg_2 as u64);
///
/// // Compute homomorphically a subtraction
/// sks.smart_sub_assign_parallelized(&mut ctxt_1, &mut ctxt_2);
///
/// // Decrypt:
/// let res = cks.decrypt(&ctxt_1);
/// assert_eq!(msg_1.wrapping_sub(msg_2) as u64, res);
/// ```
pub fn smart_sub_assign_parallelized(
&self,
ctxt_left: &mut RadixCiphertext,
ctxt_right: &mut RadixCiphertext,
) {
// If the ciphertext cannot be negated without exceeding the capacity of a ciphertext
if !self.is_neg_possible(ctxt_right) {
self.full_propagate_parallelized(ctxt_right);
}
// If the ciphertext cannot be added together without exceeding the capacity of a ciphertext
if !self.is_sub_possible(ctxt_left, ctxt_right) {
rayon::join(
|| self.full_propagate_parallelized(ctxt_left),
|| self.full_propagate_parallelized(ctxt_right),
);
}
self.unchecked_sub_assign(ctxt_left, ctxt_right);
}
}