Fix to_dlpack (#50138)

* fix to_dlpack for loop

* fix reference count

paddle/fluid/framework/dlpack_tensor.cc

@@ -134,6 +134,58 @@ struct DLDeviceVisitor
 };
 }  // namespace internal
 
+struct PaddleDLMTensor {
+  phi::DenseTensor handle;
+  DLManagedTensor tensor;
+};
+
+void deleter(DLManagedTensor *arg) {
+  delete[] arg->dl_tensor.shape;
+  delete[] arg->dl_tensor.strides;
+  delete static_cast<PaddleDLMTensor *>(arg->manager_ctx);
+}
+
+DLManagedTensor *toDLPack(const phi::DenseTensor &src) {
+  PaddleDLMTensor *pdDLMTensor(new PaddleDLMTensor);
+  pdDLMTensor->handle = const_cast<phi::DenseTensor &>(src);
+  pdDLMTensor->tensor.manager_ctx = pdDLMTensor;
+  pdDLMTensor->tensor.deleter = &deleter;
+  pdDLMTensor->tensor.dl_tensor.data = const_cast<void *>(src.data());
+
+  // init ndim
+  using DimType = decltype(pdDLMTensor->tensor.dl_tensor.ndim);  // int
+  pdDLMTensor->tensor.dl_tensor.ndim = static_cast<DimType>(src.dims().size());
+  DimType ndim = pdDLMTensor->tensor.dl_tensor.ndim;
+
+  // init shape
+  auto shape = new int64_t[ndim];
+  for (DimType i = 0; i < ndim; ++i) {
+    shape[i] = src.dims()[i];
+  }
+  pdDLMTensor->tensor.dl_tensor.shape = shape;
+
+  // init stride
+  auto strides = new int64_t[ndim];
+  for (DimType i = 0; i < ndim; ++i) {
+    strides[i] = 1;
+  }
+  for (DimType i = ndim - 2; i >= 0; --i) {
+    strides[i] = shape[i + 1] * strides[i + 1];
+  }
+  pdDLMTensor->tensor.dl_tensor.strides = strides;
+
+  // init device, DLDevice type with device_type and device_id
+  auto place = src.place();
+  pdDLMTensor->tensor.dl_tensor.device =
+      paddle::platform::VisitPlace(place, internal::DLDeviceVisitor());
+
+  pdDLMTensor->tensor.dl_tensor.dtype = internal::GetDLDataTypeFromTypeIndex(
+      framework::TransToProtoVarType(src.dtype()));
+
+  pdDLMTensor->tensor.dl_tensor.byte_offset = 0;
+  return &(pdDLMTensor->tensor);
+}
+
 DLPackTensor::DLPackTensor(const phi::DenseTensor &tensor, LaneType lanes) {
   // init data, data buffer
   t_.data = const_cast<void *>(tensor.data());

paddle/fluid/framework/dlpack_tensor.h

@@ -44,5 +44,7 @@ class DLPackTensor {
   ShapeType shape_[DDim::kMaxRank];
 };
 
+DLManagedTensor* toDLPack(const phi::DenseTensor& src);
+
 }  // namespace framework
 }  // namespace paddle

paddle/fluid/pybind/tensor.cc

@@ -473,22 +473,15 @@ void BindTensor(pybind11::module &m) {  // NOLINT
            )DOC")
       .def("_to_dlpack",
            [](phi::DenseTensor &self) {
-             DLPackTensor dlpack_tensor(self, 1);
-             DLManagedTensor *dmt = dlpack_tensor.ToDLManagedTensor();
-             auto capsule = py::capsule(
+             DLManagedTensor *dmt = framework::toDLPack(self);
+             auto capsule = pybind11::capsule(
                  static_cast<void *>(dmt), "dltensor", [](PyObject *ptr) {
-                   if (ptr) {
-                     auto dltensor = new DLManagedTensor;
-                     try {
-                       dltensor = reinterpret_cast<DLManagedTensor *>(
-                           PyCapsule_GetPointer(ptr, "used_dltensor"));
+                   if (!PyCapsule_IsValid(ptr, "dltensor")) {
                      return;
-                     } catch (...) {
-                       dltensor = reinterpret_cast<DLManagedTensor *>(
-                           PyCapsule_GetPointer(ptr, "dltensor"));
-                     }
-                     dltensor->deleter(dltensor);
                    }
+                   DLManagedTensor *dmt = static_cast<DLManagedTensor *>(
+                       PyCapsule_GetPointer(ptr, "dltensor"));
+                   dmt->deleter(dmt);
                  });
              return capsule;
            })

python/paddle/tests/test_dlpack.py

@@ -116,6 +116,12 @@ class TestDLPack(unittest.TestCase):
                 dlpack = paddle.utils.dlpack.to_dlpack(a)
                 b = paddle.utils.dlpack.from_dlpack(dlpack)
 
+    def test_to_dlpack_for_loop(self):
+        # See Paddle issue 50120
+        for i in range(10):
+            x = paddle.rand([3, 5])
+            dlpack = paddle.utils.dlpack.to_dlpack(x)
+
 
 class TestRaiseError(unittest.TestCase):
     def test_from_dlpack_raise_type_error(self):