fix: correctly set degree

tfhe/src/integer/server_key/comparator.rs

@@ -2,7 +2,7 @@ use super::ServerKey;
 use crate::integer::ciphertext::boolean_value::BooleanBlock;
 use crate::integer::ciphertext::IntegerRadixCiphertext;
 use crate::shortint::server_key::LookupTableOwned;
-use crate::shortint::Ciphertext;
+use crate::shortint::{ciphertext::Degree, Ciphertext};
 
 /// Used for compare_blocks_with_zero
 #[derive(Clone, Copy)]
@@ -407,8 +407,9 @@ impl<'a> Comparator<'a> {
 
             let maybe_lhs = self.server_key.key.apply_lookup_table(&lhs_block, lhs_lut);
             let maybe_rhs = self.server_key.key.apply_lookup_table(&rhs_block, rhs_lut);
-
-            let r = self.server_key.key.unchecked_add(&maybe_lhs, &maybe_rhs);
+            let mut r = self.server_key.key.unchecked_add(&maybe_lhs, &maybe_rhs);
+            // Either maybe_lhs or maybe_rhs is zero, which means that the degree is tighter.
+            r.degree = Degree::new(self.server_key.message_modulus().0 - 1);
             result.push(r);
         }
 

tfhe/src/integer/server_key/radix/tests.rs

@@ -1,6 +1,7 @@
 use crate::integer::keycache::KEY_CACHE;
 use crate::integer::server_key::radix_parallel::tests_cases_unsigned::*;
 use crate::integer::server_key::radix_parallel::tests_unsigned::test_add::smart_add_test;
+use crate::integer::server_key::radix_parallel::tests_unsigned::test_comparison::test_unchecked_minmax;
 use crate::integer::server_key::radix_parallel::tests_unsigned::test_neg::smart_neg_test;
 use crate::integer::server_key::radix_parallel::tests_unsigned::test_slice::{
     default_scalar_bitslice_assign_test, default_scalar_bitslice_test,
@@ -117,6 +118,16 @@ create_parametrized_test_classical_params!(integer_default_scalar_slice);
 create_parametrized_test_classical_params!(integer_default_scalar_slice_assign);
 create_parametrized_test_classical_params!(integer_smart_scalar_slice);
 create_parametrized_test_classical_params!(integer_smart_scalar_slice_assign);
+create_parametrized_test!(integer_unchecked_min {
+    coverage => {
+        COVERAGE_PARAM_MESSAGE_2_CARRY_2_KS_PBS
+    },
+    no_coverage => {
+        PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64,
+        PARAM_MESSAGE_3_CARRY_3_KS_PBS_GAUSSIAN_2M64,
+        PARAM_MESSAGE_4_CARRY_4_KS_PBS_GAUSSIAN_2M64
+    }
+});
 
 fn integer_encrypt_decrypt(param: ClassicPBSParameters) {
     let (cks, _) = KEY_CACHE.get_from_params(param, IntegerKeyKind::Radix);
@@ -800,3 +811,8 @@ fn integer_smart_scalar_slice_assign(param: ClassicPBSParameters) {
     let executor = CpuFunctionExecutor::new(&ServerKey::smart_scalar_bitslice_assign);
     smart_scalar_bitslice_assign_test(param, executor);
 }
+
+fn integer_unchecked_min(param: ClassicPBSParameters) {
+    let executor = CpuFunctionExecutor::new(&ServerKey::unchecked_min);
+    test_unchecked_minmax(param, 2, executor, std::cmp::min::<u64>);
+}

tfhe/src/shortint/ciphertext/common.rs

@@ -143,7 +143,7 @@ impl MaxDegree {
     }
 }
 
-/// This tracks the number of operations that has been done.
+/// The maximum value a given ciphertext can have. This helps with optimizations.
 #[derive(
     Debug, PartialEq, Eq, PartialOrd, Ord, Copy, Clone, Serialize, Deserialize, Versionize,
 )]