Mullapudi2016-gpu: Copy output buffer data to host

test/generator/alias_aottest.cpp

@@ -52,6 +52,7 @@ int main(int argc, char **argv) {
     output.fill(0);
     output.copy_to_host();
     alias_Mullapudi2016(input, output);
+    output.copy_to_host();
     input.for_each_element([=](int x) {
         assert(output(x) == input(x) + 2016);
     });

test/generator/autograd_aottest.cpp

@@ -110,6 +110,17 @@ int main(int argc, char **argv) {
         exit(1);
     }
 
+    grad_loss_out_wrt_a.copy_to_host();
+    grad_loss_out_wrt_b.copy_to_host();
+    grad_loss_out_wrt_c.copy_to_host();
+    dummy_grad_loss_output_wrt_lut.copy_to_host();
+    dummy_grad_loss_output_wrt_lut_indices.copy_to_host();
+    dummy_grad_loss_output_lut_wrt_input_a.copy_to_host();
+    dummy_grad_loss_output_lut_wrt_input_b.copy_to_host();
+    dummy_grad_loss_output_lut_wrt_input_c.copy_to_host();
+    grad_loss_output_lut_wrt_lut.copy_to_host();
+    grad_loss_output_lut_wrt_lut_indices.copy_to_host();
+
     // Although the values are float, all should be exact results,
     // so we don't need to worry about comparing vs. an epsilon
     grad_loss_out_wrt_a.for_each_element([&](int x) {
@@ -118,18 +129,21 @@ int main(int argc, char **argv) {
         float actual = grad_loss_out_wrt_a(x);
         assert(expected == actual);
     });
+
     grad_loss_out_wrt_b.for_each_element([&](int x) {
         // ∂𝐿/∂b = b * 44 * L
         float expected = L(x) * b(x) * 44.f;
         float actual = grad_loss_out_wrt_b(x);
         assert(expected == actual);
     });
+
     grad_loss_out_wrt_c.for_each_element([&](int x) {
         // ∂𝐿/∂c = 11 * L
         float expected = L(x) * 11.f;
         float actual = grad_loss_out_wrt_c(x);
         assert(expected == actual);
     });
+
     dummy_grad_loss_output_wrt_lut.for_each_value([](float f) { assert(f == 0.f); });
     dummy_grad_loss_output_wrt_lut_indices.for_each_value([](float f) { assert(f == 0.f); });
     dummy_grad_loss_output_lut_wrt_input_a.for_each_value([](float f) { assert(f == 0.f); });