add test for matrix_cl.setZero()

Author: SteveBronder

stan/math/opencl/matrix_cl.hpp

@@ -515,17 +515,18 @@ class matrix_cl : public matrix_cl_base {
     std::vector<cl::Event> read_write_events(read_write_size, cl::Event{});
     auto&& read_events_vec = this->read_events();
     auto&& write_events_vec = this->write_events();
-    for (std::size_t i = 0; i < write_events_size; ++i) {
+    for (std::size_t i = 0; i < read_events_size; ++i) {
       read_write_events[i] = read_events_vec[i];
     }
-    for (std::size_t i = write_events_size, j = 0; i < read_write_size;
+    for (std::size_t i = read_events_size, j = 0; j < write_events_size;
          ++i, ++j) {
       read_write_events[i] = write_events_vec[j];
     }
     try {
       opencl_context.queue().enqueueFillBuffer(buffer_cl_, static_cast<T>(0), 0,
                                                sizeof(T) * this->size(),
                                                &read_write_events, &zero_event);
+      zero_event.wait();
     } catch (const cl::Error& e) {
       check_opencl_error("setZero", e);
     }

test/unit/math/opencl/matrix_cl_test.cpp

@@ -77,4 +77,18 @@ TEST(MathMatrixCL, assignment) {
   EXPECT_EQ(nullptr, mat1_cl.buffer()());
 }
 
+TEST(MathMatrixCL, setZeroFun) {
+  using stan::math::matrix_cl;
+  Eigen::Matrix<double, 2, 2> mat_1;
+  mat_1 << 1, 2, 3, 4;
+  matrix_cl<double> mat1_cl(mat_1);
+  mat1_cl.setZero();
+  Eigen::Matrix<double, 2, 2> mat_1_fromcl
+      = stan::math::from_matrix_cl(mat1_cl);
+  EXPECT_EQ(mat_1_fromcl(0), 0);
+  EXPECT_EQ(mat_1_fromcl(1), 0);
+  EXPECT_EQ(mat_1_fromcl(2), 0);
+  EXPECT_EQ(mat_1_fromcl(3), 0);
+}
+
 #endif

test/unit/math/rev/core/var_test.cpp

@@ -960,6 +960,19 @@ TEST_F(AgradRev, assign_nan_matvar) {
   EXPECT_MATRIX_EQ(z_ans_adj, z.adj());
 }
 
+/**
+ * For var<Matrix> and Matrix<var>, we need to make sure
+ *  the tape, when going through reverse mode, leads to the same outcomes.
+ * In the case where we declare a var<Matrix> without initializing it, aka
+ * `var_value<Eigen::MatrixXd>`, we need to think about what the equivalent
+ *  behavior is for `Eigen::Matrix<var, -1, -1>`.
+ * When default constructing `Eigen::Matrix<var, -1, -1>` we would have an array of `var` types
+ * with `nullptr` as the vari. The first assignment to that array would then
+ * just copy the vari pointer from the other array. This is the behavior we
+ * want to mimic for `var_value<Eigen::MatrixXd>`. So in this test show that
+ * for uninitialized `var_value<Eigen::MatrixXd>`, we can assign it and the
+ * adjoints are the same as x.
+ */
 TEST_F(AgradRev, assign_nullptr_var) {
   using stan::math::var_value;
   using var_vector = var_value<Eigen::Matrix<double, -1, 1>>;