Fix uint256_mul_div_mod bug. (#1320)

lambdaclass · Jul 10, 2023 · ce73104 · ce73104 · github-actions · Jul 10, 2023
1 parent 1b860b7
commit ce73104
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 #### Upcoming Changes
 
+* fix: fix `UINT256_MUL_DIV_MOD` hint [#1320](https://github.com/lambdaclass/cairo-vm/pull/1320)
+
 * feat: add dependency installation script `install.sh` [#1298](https://github.com/lambdaclass/cairo-vm/pull/1298)
 
 * fix: specify resolver version 2 in the virtual workspace's manifest [#1311](https://github.com/lambdaclass/cairo-vm/pull/1311)

diff --git a/vm/src/hint_processor/builtin_hint_processor/uint256_utils.rs b/vm/src/hint_processor/builtin_hint_processor/uint256_utils.rs
@@ -431,10 +431,10 @@ pub fn uint256_mul_div_mod(
     let div_high = div_high.as_ref();
 
     // Main Logic
-    let a = a_high.shl(128_usize) + a_low;
-    let b = b_high.shl(128_usize) + b_low;
-    let div = div_high.shl(128_usize) + div_low;
-    let (quotient, remainder) = (a.to_biguint() * b.to_biguint()).div_mod_floor(&div.to_biguint());
+    let a = a_high.to_biguint().shl(128_usize) + a_low.to_biguint();
+    let b = b_high.to_biguint().shl(128_usize) + b_low.to_biguint();
+    let div = div_high.to_biguint().shl(128_usize) + div_low.to_biguint();
+    let (quotient, remainder) = (a * b).div_mod_floor(&div);
 
     // ids.quotient_low.low
     vm.insert_value(
Benchmark suite	Current: `ce73104`	Previous: `1b860b7`	Ratio
`add_u64_with_felt/1`	`4` ns/iter (`± 0`)	`3` ns/iter (`± 0`)	`1.33`
`add_u64_with_felt/3`	`2` ns/iter (`± 0`)	`1` ns/iter (`± 0`)	`2`
`add_u64_with_felt/4`	`2` ns/iter (`± 0`)	`1` ns/iter (`± 0`)	`2`
`add_u64_with_felt/5`	`2` ns/iter (`± 0`)	`1` ns/iter (`± 0`)	`2`
`add_u64_with_felt/6`	`5` ns/iter (`± 0`)	`3` ns/iter (`± 0`)	`1.67`
`add_u64_with_felt/7`	`5` ns/iter (`± 0`)	`3` ns/iter (`± 0`)	`1.67`
`add_u64_with_felt/8`	`3` ns/iter (`± 0`)	`2` ns/iter (`± 0`)	`1.50`