feat(imperative/jit): let trace support empty IO

GitOrigin-RevId: 97a55242bf

imperative/src/impl/opr_utility.cpp

@@ -45,7 +45,10 @@ InputCallback::InputCallback(cg::ComputingGraph& graph, callback_t callback,
     if(m_use_static_shape){
         mgb_assert(m_output_shape.ndim);
     }
-    add_output(None)->add_flag(VarNode::Flag::NO_SYS_MEM_ALLOC).dtype(dt);
+    add_output(None)
+            ->add_flag(VarNode::Flag::ALLOW_EMPTY_SHAPE)
+            .add_flag(VarNode::Flag::NO_SYS_MEM_ALLOC)
+            .dtype(dt);
     add_output(None)
             ->add_flag(VarNode::Flag::ALLOW_EMPTY_SHAPE)
             .add_flag(VarNode::Flag::NO_SYS_MEM_ALLOC)
@@ -109,6 +112,11 @@ void InputCallback::scn_do_execute() {
     if (m_use_static_shape) {
         mgb_assert(dev_tensor.shape().eq_shape(m_output_shape));
     }
+    if (dev_tensor.empty()) {
+        auto layout = dev_tensor.layout();
+        layout.init_contiguous_stride();
+        dev_tensor.reset(dev_tensor.storage(), layout);
+    }
     output(0)->reset_dev_tensor_from_tensor(dev_tensor);
 }
 
@@ -172,6 +180,7 @@ cg::OperatorNodeBase::NodeProp* OutputCallback::do_make_node_prop() const {
     };
     m_use_host_value = m_param.prefer_host_value && host_value_avail();
     dep_types[0] = m_use_host_value ? NodeProp::DepType::HOST_VALUE : NodeProp::DepType::DEV_VALUE;
+    dep_types[0] |= NodeProp::DepType::VALUE_ALLOW_EMPTY;
     prop->reset_dep_type(input(), dep_types);
     return prop;
 }

imperative/src/impl/proxy_graph.cpp

@@ -564,11 +564,7 @@ void ProxyGraph::init_output_tensor(const SmallVector<Tensor*>& outputs) {
             mgb_assert(var->comp_node() == tensor->comp_node() &&
                         var->shape().eq_shape(layout) &&
                         var->dtype() == layout.dtype);
-            if (!tensor->layout().is_empty()) {
-                var->assign_dev_tensor_from_tensor(tensor->dev_tensor());
-            } else {
-                var->m_dev_tensor.storage({var->comp_node()});
-            }
+            var->assign_dev_tensor_from_tensor(tensor->dev_tensor());
             ++ j;
         }
         chk.mem_alloc_status.set_from_owner_var();

src/core/impl/graph/var_node.cpp

@@ -361,9 +361,19 @@ VarNode& VarNode::reset_dev_tensor_from_tensor(const DeviceTensorND& value) {
 }
 
 void VarNode::assign_dev_tensor_from_tensor(const DeviceTensorND& value) {
-    mgb_assert(value.layout().is_contiguous() &&
+    mgb_assert((value.layout().is_contiguous() || value.empty()) &&
                m_dev_tensor.dtype() == value.dtype() &&
                m_dev_tensor.format() == value.format());
+    if (value.empty()) {
+        mgb_assert(value.shape_valid() && value.layout().is_empty());
+        bool allow_empty = contain_flag(VarNode::Flag::ALLOW_EMPTY_SHAPE);
+        auto &&recv = owner_graph()->var_receiver_in_current_comp_seq(this);
+        mgb_throw_if(!allow_empty || !recv.is_empty_allowed(),
+                GraphError,
+                "assign empty tensor to var %s, but allowed=%d, receiver=%s",
+                cg::dump_var_info({this}).c_str(),
+                allow_empty, recv.to_string().c_str());
+    }
     if (cg::is_static_var_shape(this)) {
         mgb_assert(shape().eq_shape(value.shape()),
                    "shape mismatch for static inferrable var when setting dev "

src/core/include/megbrain/graph/var_node.h

@@ -480,8 +480,8 @@ class VarNode final: public GraphNodeBase {
          *
          * \param src_var the var node to provide dev tensor, which must have
          *      been initialized, and does not have to be in the same computing
-         *      graph. Its value must be contiguous. It can also be placed on a
-         *      different comp node.
+         *      graph. Its value must be contiguous or empty. It can also be
+         *      placed on a different comp node.
          *
          * \return whether memory forwarding succeeds; if false is returned, a
          *      new tensor would be allocated and its value is copied from src
@@ -495,8 +495,8 @@ class VarNode final: public GraphNodeBase {
          * This function should only be called by this var's owner operator and
          * this var must have NO_SYS_MEM_ALLOC flag
          *
-         * \param value the tensor to be used; it must be contiguous and be
-         *      placed on the same comp node of this var.
+         * \param value the tensor to be used; it must be contiguous or empty
+         *       and be placed on the same comp node of this var.
          */
         VarNode& reset_dev_tensor_from_tensor(const DeviceTensorND &value);
 

src/core/test/graph/misc.cpp

@@ -10,6 +10,7 @@
  */
 
 #include "megbrain/opr/io.h"
+#include "megbrain/opr/basic_arith.h"
 #include "megbrain/opr/basic_arith_wrapper.h"
 #include "megbrain/opr/dnn/convolution.h"
 #include "megbrain/opr/utility.h"
@@ -2336,4 +2337,95 @@ TEST(TestGraph, DynamicOutput) {
     MGB_ASSERT_TENSOR_NEAR(expect_spl_0_0, result_spl_0_0, 1e-4);
 }
 
+namespace {
+// used for test reset_dev_tensor_from_tensor
+MGB_DEFINE_OPR_CLASS(MaybeEmptyTensorOpr, cg::SingleCNOperatorNodeBase)// {
+    DeviceTensorND m_dv;
+
+    void init_output_comp_node() override {
+        output(0)->comp_node(m_dv.comp_node());
+        comp_node(m_dv.comp_node());
+    }
+
+    void scn_do_execute() override {
+        output(0)->reset_dev_tensor_from_tensor(m_dv);
+    }
+
+    void init_output_static_infer_desc() override {
+        using namespace cg::static_infer;
+        auto &&mgr = owner_graph()->static_infer_manager();
+        mgr.register_shape_infer(output(0),
+                ShapeInferDesc::make_const(m_dv.shape()));
+    }
+
+    public:
+        MaybeEmptyTensorOpr(ComputingGraph &graph,
+                const DeviceTensorND &dv, const OperatorNodeConfig &config):
+            Super(&graph, config, "", {}), m_dv{dv} {
+            add_output(None)
+                ->add_flag(cg::VarNode::Flag::NO_SYS_MEM_ALLOC)
+                .add_flag(VarNode::Flag::ALLOW_EMPTY_SHAPE)
+                .dtype(dv.dtype());
+        }
+
+        static SymbolVar make(ComputingGraph &graph, const DeviceTensorND &dv,
+                const OperatorNodeConfig &config = {}) {
+            return graph.insert_opr(std::make_unique<MaybeEmptyTensorOpr>(
+                        graph, dv, config))->output(0);
+        }
+};
+
+} // anonymous namespace
+
+MGB_DYN_TYPE_OBJ_FINAL_IMPL(MaybeEmptyTensorOpr);
+
+TEST(TestMemReuse, ResetEmptyDevTensor) {
+    // reciver opr allow empty tensor as input
+    auto allow_empty = [](const TensorShape& inp_shp) {
+        HostTensorGenerator<> gen;
+        auto g = ComputingGraph::make();
+        auto host_x1 = gen(inp_shp),
+             host_x2 = gen(inp_shp);
+        DeviceTensorND dev_x1, dev_x2;
+        dev_x1.copy_from(*host_x1), dev_x2.copy_from(*host_x2);
+        auto x1 = MaybeEmptyTensorOpr::make(*g, dev_x1, {"x1"}),
+             x2 = MaybeEmptyTensorOpr::make(*g, dev_x2, {"x2"}),
+             y = x1 + x2;
+        HostTensorND host_y;
+        auto func = g->compile({make_callback_copy(y, host_y)});
+        auto &&recv = x1.node()->owner_graph()->var_receiver_in_current_comp_seq(x1.node());
+        ASSERT_TRUE(recv.is_empty_allowed());
+        ASSERT_NO_THROW(func->execute().wait());
+        if (inp_shp.is_empty()) {
+            ASSERT_TRUE(host_y.empty());
+            ASSERT_TRUE(host_y.shape().is_empty());
+        }
+    };
+
+    // reciver opr do not allow empty tensor as input
+    auto forbid_empty = [](const TensorShape& inp_shp) {
+        HostTensorGenerator<> gen;
+        auto g = ComputingGraph::make();
+        auto host_x = gen(inp_shp);
+        DeviceTensorND dev_x;
+        dev_x.copy_from(*host_x);
+        auto x = MaybeEmptyTensorOpr::make(*g, dev_x, {"x"}),
+             y = opr::Reduce::make(x, {opr::Reduce::Mode::MAX, 0});
+        HostTensorND host_y;
+        auto func = g->compile({make_callback_copy(y, host_y)});
+        auto &&recv = x.node()->owner_graph()->var_receiver_in_current_comp_seq(x.node());
+        ASSERT_TRUE(!recv.is_empty_allowed());
+        if (inp_shp.is_empty()) {
+            ASSERT_ANY_THROW(func->execute().wait());
+        } else {
+            ASSERT_NO_THROW(func->execute().wait());
+        }
+    };
+
+    allow_empty({2, 3, 4, 5});
+    allow_empty({2, 0, 3, 4});
+    forbid_empty({4, 5, 6, 7});
+    forbid_empty({8, 0, 0, 9});
+}
+
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