fix(imperative/src): fix dot backward error

GitOrigin-RevId: 02ba44a0e6d8cd2ca863ae0058542b260e0b755d

imperative/python/test/unit/core/test_autodiff.py

@@ -442,3 +442,18 @@ def test_removeAxis():
 
     grad(y, F.ones_like(y))
     np.testing.assert_equal(np.ones((3, 3, 1, 1), dtype=np.float32), x.grad.numpy())
+
+
+def test_dot():
+    x = np.random.rand(2, 2).astype("float32")
+    x = mge.Tensor(x)
+    u = F.ones((2,))
+    v = F.ones((2,))
+    grad = Grad().wrt(x, callback=save_to(x))
+
+    def f(x):
+        return F.dot(u, F.matmul(x, v))
+
+    y = f(x)
+    grad(y, F.ones_like(y))
+    np.testing.assert_equal(np.ones((2, 2), dtype=np.float32), x.grad.numpy())

imperative/src/impl/ops/tensor_manip.cpp

@@ -33,7 +33,7 @@ DispatchMode decide_dispatch_mode(
         const SmallVector<LogicalTensorDesc>& inputs) {
     bool host_computable = true;
     for (auto&& inp : inputs) {
-        // FIXME(czh): remove value chech after proxy graph's
+        // FIXME(czh): remove value check after proxy graph's
         // apply_on_device_tensornd is supported and output Tensor
         // is made before add_task.
         // then if layout is valid, ptr->layout must be ready
@@ -50,9 +50,18 @@ void apply_on_device_tensornd(
         const SmallVector<DeviceTensorND>& inputs,
         SmallVector<DeviceTensorND>* outputs) {
     auto&& op_def = def.cast_final_safe<GetVarShape>();
-    mgb_assert(inputs.size() == 1, "GetVarShape take 1 input, got %lu", inputs.size());
-    auto&& inp = inputs[0];
-    auto&& shp = inp.layout();
+
+    TensorShape shp;
+    if (inputs.size() == 1) {
+        shp = inputs[0].layout();
+    } else {
+        TensorShapeArray src(inputs.size());
+        for (size_t i = 0; i < inputs.size(); ++i) {
+            src[i] = inputs[i].layout();
+        }
+        megdnn::Elemwise::deduce_shape(src, shp);
+    }
+
     mgb_assert(shp.ndim != 0, "input shape invalid");
     mgb_assert((*outputs)[0].comp_node() == CompNode::default_cpu(),
         "GetVarShape's apply_on_device_tensornd should receive default_cpu outputs.");
@@ -99,27 +108,36 @@ std::tuple<SmallVector<LogicalTensorDesc>, bool> infer_output_attrs_fallible(
         const OpDef& def,
         const SmallVector<LogicalTensorDesc>& inputs) {
     auto&& op_def = def.cast_final_safe<GetVarShape>();
-    mgb_assert(inputs.size() == 1, "GetVarShape take 1 input, got %lu", inputs.size());
     auto&& desc = inputs[0];
-    if (!desc.layout.ndim) {
+    TensorShape shp;
+    if (inputs.size() == 1) {
+        shp = desc.layout;
+    } else {
+        TensorShapeArray src(inputs.size());
+        for (size_t i = 0; i < inputs.size(); ++i) {
+            src[i] = inputs[i].layout;
+        }
+        megdnn::Elemwise::deduce_shape(src, shp);
+    }
+    if (!shp.ndim) {
         return {{{TensorLayout(dtype::Int32()), desc.comp_node}}, false};
     }
     DeviceTensorND value;
     if (op_def.axis == opr::GetVarShape::Param::INVALID_AXIS) {
-        value = DeviceTensorND(CompNode::default_cpu(), {desc.layout.ndim}, dtype::Int32());
+        value = DeviceTensorND(CompNode::default_cpu(), {shp.ndim}, dtype::Int32());
         auto* ptr = value.ptr<dt_int32>();
-        for (size_t i = 0; i < desc.layout.ndim; ++i) {
-            ptr[i] = desc.layout[i];
+        for (size_t i = 0; i < shp.ndim; ++i) {
+            ptr[i] = shp[i];
         }
     }else{
         int32_t axis = op_def.axis;
         if (axis < 0) {
-            axis += desc.layout.ndim;
+            axis += shp.ndim;
         }
-        mgb_assert(axis >= 0 && axis < (int32_t)desc.layout.ndim);
+        mgb_assert(axis >= 0 && axis < (int32_t)shp.ndim);
         value = DeviceTensorND(CompNode::default_cpu(), {1}, dtype::Int32());
         auto* ptr = value.ptr<dt_int32>();
-        ptr[0] = desc.layout[axis];
+        ptr[0] = shp[axis];
     }
     return {{{value.layout(), desc.comp_node, std::move(value)}}, true};
 }