diff --git a/misc/test_gpu_sm_op.py b/misc/test_gpu_sm_op.py
index e7f640db8d1dfd..2de61af1d9a482 100644
--- a/misc/test_gpu_sm_op.py
+++ b/misc/test_gpu_sm_op.py
@@ -25,7 +25,7 @@
             data_rvs=rvs).astype(np_dtype)
 S2 = random(rows, cols, density=0.5, random_state=rng,
             data_rvs=rvs).astype(np_dtype)
-# S2 = S2.T
+
 nnz_A = len(S1.data)
 nnz_B = len(S2.data)
 
diff --git a/taichi/program/sparse_matrix.h b/taichi/program/sparse_matrix.h
index 859f4eeea6a4d1..eaab4db2cd7988 100644
--- a/taichi/program/sparse_matrix.h
+++ b/taichi/program/sparse_matrix.h
@@ -225,6 +225,7 @@ class CuSparseMatrix : public SparseMatrix {
 
   virtual ~CuSparseMatrix();
 
+  // TODO: Overload +=, -= and *=
   friend std::unique_ptr<SparseMatrix> operator+(const CuSparseMatrix &lhs,
                                                  const CuSparseMatrix &rhs) {
     auto m = lhs.addition(rhs, 1.0, 1.0);
@@ -236,7 +237,6 @@ class CuSparseMatrix : public SparseMatrix {
     return lhs.addition(rhs, 1.0, -1.0);
   };
 
-  // TODO: Overload *=
   friend std::unique_ptr<SparseMatrix> operator*(const CuSparseMatrix &sm,
                                                  float scale) {
     return sm.addition(sm, scale, 0.0);