diff --git a/.github/workflows/run-unit-tests.yml b/.github/workflows/run-unit-tests.yml
index 6fe312d..2811fca 100644
--- a/.github/workflows/run-unit-tests.yml
+++ b/.github/workflows/run-unit-tests.yml
@@ -2,9 +2,14 @@ name: run-unit-tests
 
 on:
   pull_request:
+    types: [review_requested, ready_for_review, synchronize, opened, reopened]
     branches:
       - main
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   run-unit-tests:
     if: github.event.pull_request.draft == false
diff --git a/src/matrix/mat.rs b/src/matrix/mat.rs
index 02a042b..b3d93b6 100644
--- a/src/matrix/mat.rs
+++ b/src/matrix/mat.rs
@@ -364,6 +364,21 @@ impl Not for Matrix<bool> {
     }
 }
 
+// implement for &Matrix<bool>
+impl<'a> Not for &'a Matrix<bool> {
+    type Output = Matrix<bool>;
+
+    fn not(self) -> Matrix<bool> {
+        // Invert each boolean element in the matrix
+        let data = self.data.iter().map(|&v| !v).collect();
+        Matrix {
+            rows: self.rows,
+            cols: self.cols,
+            data,
+        }
+    }
+}
+
 pub type FloatMatrix = Matrix<f64>;
 pub type BoolMatrix = Matrix<bool>;
 pub type IntMatrix = Matrix<i32>;