fixed a bug with block size

src/targets/gpu/device/pack.cpp

@@ -25,7 +25,7 @@ void pack_a(hipStream_t stream, const argument& result, const argument& arg)
         auto* in_ptr          = device_cast(input.data());
         visit_tensor_size(out_lens.size(), [&](auto out_dim) {
             hip_tensor_descriptor<out_dim> desc(comp_shape);
-            gs_launch(stream, nelements)([=](auto ii) {
+            gs_launch(stream, nelements, 256)([=](auto ii) {
                 const size_t nb    = 4;
                 auto idx           = desc.multi(ii);
                 std::size_t i_m    = idx[dim_1];
@@ -56,7 +56,7 @@ void pack_b(hipStream_t stream, const argument& result, const argument& arg)
         auto* in_ptr          = device_cast(input.data());
         visit_tensor_size(out_lens.size(), [&](auto out_dim) {
             hip_tensor_descriptor<out_dim> desc(comp_shape);
-            gs_launch(stream, nelements)([=](auto ii) {
+            gs_launch(stream, nelements, 256)([=](auto ii) {
                 const size_t nb    = 4;
                 auto idx           = desc.multi(ii);
                 std::size_t i_n    = idx[dim_1];