perf(mge/utils): move convert_input into C++

GitOrigin-RevId: 0d1cd362511d2d423faaeffd9d80710747cf05f2

imperative/python/megengine/core/tensor/array_method.py

@@ -19,6 +19,7 @@ from .._imperative_rt.core2 import (
     SymbolVar,
     Tensor,
     apply,
+    astype_cpp,
     broadcast_cpp,
     dtype_promotion,
 )
@@ -27,14 +28,7 @@ from .._imperative_rt.core2 import reshape_cpp, squeeze_cpp, transpose_cpp
 from ..ops import builtin
 from . import amp
 from .indexing import getitem, setitem
-from .utils import (
-    _normalize_axis,
-    astensor1d,
-    astype,
-    cast_tensors,
-    make_shape_tuple,
-    subgraph,
-)
+from .utils import _normalize_axis, astensor1d, cast_tensors, make_shape_tuple, subgraph
 
 _ElwMod = builtin.Elemwise.Mode
 
@@ -605,7 +599,7 @@ class ArrayMethodMixin(abc.ABC):
         r"""Returns a :class:`Tensor` with the same data and number of elements
         with the specified :attr:`~.Tensor.dtype`.
         """
-        return astype(self, dtype)
+        return astype_cpp(self, dtype)
 
     def reshape(self, *args):
         r"""See :func:`~.reshape`."""

imperative/python/megengine/core/tensor/utils.py

@@ -20,6 +20,9 @@ from .._imperative_rt.core2 import (
     _get_convert_inputs,
     _set_convert_inputs,
     apply,
+    astype_cpp,
+    convert_inputs_cpp,
+    convert_single_value_cpp,
     dtype_promotion,
     get_device,
     make_shape_tuple,
@@ -55,53 +58,14 @@ def concatenate(inputs, axis=0, *, device=None):
     return result
 
 
-def astype(x, dtype):
-    dtype = np.dtype(dtype)
-    if not is_dtype_equal(x.dtype, dtype):
-        (x,) = apply(builtin.TypeCvt(dtype=dtype), x)
-    return x
-
-
 def convert_single_value(v, *, dtype=None, device=None):
-    if isinstance(v, (Tensor, SymbolVar)):
-        if not is_quantize(v.dtype):
-            v = astype(v, dtype)
-    else:
-        v = Const(v, dtype, device, None)
-    return v
+    return convert_single_value_cpp(v, dtype, device)
 
 
 def convert_inputs(*args, device=None):
     if not _get_convert_inputs():
         return args
-
-    dtype = dtype_promotion(args)
-    if device is None:
-        device = get_device(args)
-    device = as_device(device)
-
-    graph = None
-    sym_type = None
-    for a in args:
-        if isinstance(a, SymbolVar):
-            if graph is None:
-                graph = a.var.graph
-                sym_type = type(a)
-            else:
-                assert graph == a.var.graph
-    args = list(args)
-    if graph is not None:
-        for i in range(len(args)):
-            if not isinstance(args[i], SymbolVar):
-                rst = make_const(graph, np.array(args[i]), device.to_c(), dtype)
-                args[i] = sym_type(rst)
-
-    def convert(value):
-        if value is None:
-            return value
-        return convert_single_value(value, dtype=dtype, device=device.to_c())
-
-    return tuple(map(convert, args))
+    return convert_inputs_cpp(*args, device)
 
 
 def cast_tensors(*args, promote=False):
@@ -146,7 +110,7 @@ def astensor1d(x, *reference, dtype=None, device=None):
         pass
     except ValueError:
         if dtype is not None and dtype != x.dtype:
-            x = astype(x, dtype)
+            x = astype_cpp(x, dtype)
         if device is not None:
             cn = as_device(device).to_c()
             (x,) = apply(builtin.Copy(comp_node=cn), x)
@@ -164,7 +128,7 @@ def astensor1d(x, *reference, dtype=None, device=None):
     if any(isinstance(i, (Tensor, SymbolVar)) for i in x):
         x = concatenate(x, device=device) if len(x) > 1 else x[0]
         if dtype is not None:
-            x = astype(x, dtype)
+            x = astype_cpp(x, dtype)
         return x
     x = Const(x, dtype, device, reference)
     return x

imperative/python/megengine/functional/nn.py

@@ -30,7 +30,6 @@ from ..core.tensor import amp, megbrain_graph
 from ..core.tensor.array_method import _elwise_apply
 from ..core.tensor.utils import (
     astensor1d,
-    astype,
     cast_tensors,
     convert_single_value,
     make_shape_tuple,

imperative/python/src/numpy_dtypes.cpp

@@ -170,6 +170,12 @@ struct _wrap {
 
 }  // anonymous namespace
 
+namespace imperative::python {
+bool dtype_equal(PyArray_Descr* dt1, PyArray_Descr* dt2) {
+    return _is_dtype_equal(dt1, dt2);
+}
+}  // namespace imperative::python
+
 #ifdef METH_FASTCALL
 #define MGE_PY_INTERFACE(NAME, FUN) \
     { #NAME, (PyCFunction)_wrap < &(FUN)> ::impl, METH_FASTCALL, nullptr }

imperative/python/src/numpy_dtypes.h

@@ -26,6 +26,11 @@
             cb(BFloat16, npy_num_bfloat16())
 
 namespace mgb {
+
+namespace imperative::python {
+bool dtype_equal(PyArray_Descr* dt1, PyArray_Descr* dt2);
+}  // namespace imperative::python
+
 //! numpy type num for intb1/2/4 type
 #define DEFINE_NPY_INTBX(n) int npy_num_intb##n();
 FOREACH_MGB_LOW_BIT(DEFINE_NPY_INTBX)

imperative/python/src/tensor.cpp

@@ -400,223 +400,6 @@ struct TensorWeakRef {
     int _use_cnt() { return wptr.use_count(); }
 };
 
-/* ============== convert inputs ============== */
-
-// map numpy.dtype.kind to priority
-inline uint8_t category_priority(char c) {
-    switch (c) {
-        case 'f':
-            return 3;  // floating-point
-        case 'i':
-            return 2;  // signed integer
-        case 'u':
-            return 2;  // unsigned integer
-        case 'b':
-            return 1;  // boolean
-        default:
-            return 0;
-    }
-}
-
-// Returns the maximum value of the priority of each type in the list `types`.
-uint8_t max_priority(SmallVector<PyArray_Descr*> types) {
-    if (types.size() == 0) {
-        return 0;
-    } else {
-        uint8_t max_p = 0;
-        for (auto&& desc : types) {
-            max_p = std::max(max_p, category_priority(desc->kind));
-        }
-        return max_p;
-    }
-}
-
-// Returns the data type with sufficient size to hold all types of
-// category `cat` in the list `types`.
-PyArray_Descr* promote_types(SmallVector<PyArray_Descr*> types, uint8_t cat) {
-    // Return value: New reference
-    SmallVector<PyArray_Descr*> used_types;
-    for (auto&& desc : types) {
-        auto&& v = category_priority(desc->kind);
-        if (v == cat) {
-            used_types.emplace_back(desc);
-        }
-    }
-    mgb_assert(used_types.size() > 0, "size of used_types is 0");
-    PyArray_Descr* res = used_types[0];
-    Py_INCREF(res);
-
-    for (size_t i = 1; i < used_types.size(); ++i) {
-        PyArray_Descr* tmp = PyArray_PromoteTypes(used_types[i], res);
-        Py_DECREF(res);
-        res = tmp;
-    }
-    return res;
-}
-
-PyArray_Descr* scalar2dtype(PyObject* arg) {
-    // Return value: New reference
-    if (PyBool_Check(arg)) {
-        auto&& descr = PyArray_DescrFromType(NPY_BOOL);
-        return descr;
-    }
-    if (PyLong_CheckExact(arg)) {
-        auto&& descr = PyArray_DescrFromType(NPY_INT32);
-        return descr;
-    }
-    if (PyFloat_CheckExact(arg)) {
-        auto&& descr = PyArray_DescrFromType(NPY_FLOAT32);
-        return descr;
-    }
-    return nullptr;
-}
-
-PyArray_Descr* _dtype_promotion(PyObject* const* args, size_t nargs) {
-    // Return value: New reference
-    SmallVector<PyArray_Descr*> tensors;
-    SmallVector<PyArray_Descr*> scalars;
-
-    bool is_tuple = false;
-    PyObject* tuple = nullptr;
-    if (nargs == 1 && (PyTuple_Check(args[0]) || PyList_Check(args[0]))) {
-        if (PyList_Check(args[0])) {
-            tuple = PyList_AsTuple(args[0]);
-        } else {
-            tuple = args[0];
-            Py_INCREF(tuple);
-        }
-        nargs = PyTuple_Size(tuple);
-        is_tuple = true;
-    }
-
-    for (size_t i = 0; i < nargs; ++i) {
-        PyObject* handle = is_tuple ? PyTuple_GetItem(tuple, i) : args[i];
-        if (handle == Py_None)
-            continue;
-        TensorWrapper* tw = TensorWrapper::try_cast(handle);
-        if (tw) {
-            mgb::DType type = tw->m_tensor->dtype();
-            auto&& descr = npy::dtype_mgb2np_descr(type);
-            Py_INCREF(descr.get());
-            tensors.emplace_back(descr.get());
-        } else {
-            if (PyArray_Check(handle) || PyArray_CheckScalar(handle)) {
-                auto&& descr = PyArray_DescrFromObject(handle, nullptr);
-                tensors.emplace_back(descr);
-                continue;
-            }
-
-            if (py::isinstance<PySymbolVar>(py::handle(handle))) {
-                auto var = py::handle(handle).cast<PySymbolVar*>();
-                mgb::DType type = var->m_node->dtype();
-                auto&& descr = npy::dtype_mgb2np_descr(type);
-                Py_INCREF(descr.get());
-                tensors.emplace_back(descr.get());
-                continue;
-            }
-
-            PyArray_Descr* descr = scalar2dtype(handle);
-            if (descr) {
-                scalars.emplace_back(descr);
-                continue;
-            }
-        }
-    }
-
-    auto max_pri_scalars = max_priority(scalars);
-    auto max_pri_tensors = max_priority(tensors);
-
-    if (max_pri_scalars <= 0 && max_pri_tensors <= 0) {
-        throw py::value_error("invalid input, no dtype avaliable");
-    }
-    PyArray_Descr* res;
-    if (max_pri_scalars > max_pri_tensors) {
-        res = promote_types(scalars, max_pri_scalars);
-    } else {
-        res = promote_types(tensors, max_pri_tensors);
-    }
-    for (auto* p : tensors) {
-        Py_DECREF(p);
-    }
-    for (auto* p : scalars) {
-        Py_DECREF(p);
-    }
-    Py_XDECREF(tuple);
-    return res;
-}
-
-CompNode _get_device(PyObject* const* args, size_t nargs) {
-    bool is_tuple = false;
-    PyObject* tuple = nullptr;
-    if (nargs == 1 && (PyTuple_Check(args[0]) || PyList_Check(args[0]))) {
-        if (PyList_Check(args[0])) {
-            tuple = PyList_AsTuple(args[0]);
-        } else {
-            tuple = args[0];
-            Py_INCREF(tuple);
-        }
-        nargs = PyTuple_Size(tuple);
-        is_tuple = true;
-    }
-    bool valid = false;
-    CompNode cn;
-    for (size_t i = 0; i < nargs; ++i) {
-        PyObject* handle = is_tuple ? PyTuple_GetItem(tuple, i) : args[i];
-        TensorWrapper* tw = TensorWrapper::try_cast(handle);
-
-        bool is_symvar = py::isinstance<PySymbolVar>(py::handle(handle));
-        if (tw || is_symvar) {
-            if (!valid) {
-                cn = tw ? tw->m_tensor->comp_node()
-                        : py::handle(handle).cast<PySymbolVar*>()->m_node->comp_node();
-                valid = true;
-            } else {
-                CompNode cn1 = tw ? tw->m_tensor->comp_node()
-                                  : py::handle(handle)
-                                               .cast<PySymbolVar*>()
-                                               ->m_node->comp_node();
-                if (cn1 != cn) {
-                    throw py::value_error(ssprintf(
-                            "ambiguous device: %s (from %s) vs %s (from %s)",
-                            cn.to_string().c_str(), cn.to_string_logical().c_str(),
-                            cn1.to_string().c_str(), cn1.to_string_logical().c_str()));
-                }
-            }
-        }
-    }
-    if (!valid) {
-        return CompNode::load(get_default_device());
-    }
-    Py_XDECREF(tuple);
-    return cn;
-}
-
-// Returns the dtype that would result from performing an arithmetic
-// operation on the provided input tensors and scalars.
-PyObject* dtype_promotion(PyObject* self, PyObject* const* args, size_t nargs) {
-    if (!nargs) {
-        PyErr_SetString(PyExc_TypeError, "empty input is not allowed");
-        return nullptr;
-    }
-    try {
-        PyArray_Descr* res = _dtype_promotion(args, nargs);
-        return py::cast(npy::dtype_np2mgb_descr(res)).release().ptr();
-    }
-    PYEXT17_TRANSLATE_EXC_RET(nullptr)
-}
-
-PyObject* get_device(PyObject* self, PyObject* const* args, size_t nargs) {
-    if (!nargs) {
-        PyErr_SetString(PyExc_TypeError, "empty input is not allowed");
-        return nullptr;
-    }
-    try {
-        CompNode cn = _get_device(args, nargs);
-        return py::cast(cn).release().ptr();
-    }
-    PYEXT17_TRANSLATE_EXC_RET(nullptr)
-}
-
 #ifdef METH_FASTCALL
 #define MGE_PY_INTERFACE(NAME, FUNC) \
     { #NAME, (PyCFunction)FUNC, METH_FASTCALL, nullptr }
@@ -640,6 +423,9 @@ WRAP_FUNC_PY35(transpose_cpp);
 WRAP_FUNC_PY35(broadcast_cpp);
 WRAP_FUNC_PY35(reshape_cpp);
 WRAP_FUNC_PY35(Const);
+WRAP_FUNC_PY35(astype_cpp);
+WRAP_FUNC_PY35(convert_single_value_cpp);
+WRAP_FUNC_PY35(convert_inputs_cpp);
 #undef WRAP_FUNC_PY35
 #define MGE_PY_INTERFACE(NAME, FUNC) \
     { #NAME, (PyCFunction)py35_##FUNC, METH_VARARGS, nullptr }
@@ -779,6 +565,9 @@ void init_tensor(py::module m) {
             MGE_PY_INTERFACE(broadcast_cpp, broadcast_cpp),
             MGE_PY_INTERFACE(reshape_cpp, reshape_cpp),
             MGE_PY_INTERFACE(Const, Const),
+            MGE_PY_INTERFACE(astype_cpp, astype_cpp),
+            MGE_PY_INTERFACE(convert_single_value_cpp, convert_single_value_cpp),
+            MGE_PY_INTERFACE(convert_inputs_cpp, convert_inputs_cpp),
             {nullptr, nullptr, 0, nullptr}};
     for (auto&& def : method_defs) {
         if (def.ml_meth != nullptr) {

imperative/python/src/tensor_utils.cpp

@@ -52,6 +52,223 @@ namespace views = ranges::views;
 
 namespace mgb::imperative::python {
 
+/* ============== convert inputs ============== */
+
+// map numpy.dtype.kind to priority
+inline uint8_t category_priority(char c) {
+    switch (c) {
+        case 'f':
+            return 3;  // floating-point
+        case 'i':
+            return 2;  // signed integer
+        case 'u':
+            return 2;  // unsigned integer
+        case 'b':
+            return 1;  // boolean
+        default:
+            return 0;
+    }
+}
+
+// Returns the maximum value of the priority of each type in the list `types`.
+uint8_t max_priority(SmallVector<PyArray_Descr*> types) {
+    if (types.size() == 0) {
+        return 0;
+    } else {
+        uint8_t max_p = 0;
+        for (auto&& desc : types) {
+            max_p = std::max(max_p, category_priority(desc->kind));
+        }
+        return max_p;
+    }
+}
+
+// Returns the data type with sufficient size to hold all types of
+// category `cat` in the list `types`.
+PyArray_Descr* promote_types(SmallVector<PyArray_Descr*> types, uint8_t cat) {
+    // Return value: New reference
+    SmallVector<PyArray_Descr*> used_types;
+    for (auto&& desc : types) {
+        auto&& v = category_priority(desc->kind);
+        if (v == cat) {
+            used_types.emplace_back(desc);
+        }
+    }
+    mgb_assert(used_types.size() > 0, "size of used_types is 0");
+    PyArray_Descr* res = used_types[0];
+    Py_INCREF(res);
+
+    for (size_t i = 1; i < used_types.size(); ++i) {
+        PyArray_Descr* tmp = PyArray_PromoteTypes(used_types[i], res);
+        Py_DECREF(res);
+        res = tmp;
+    }
+    return res;
+}
+
+PyArray_Descr* scalar2dtype(PyObject* arg) {
+    // Return value: New reference
+    if (PyBool_Check(arg)) {
+        auto&& descr = PyArray_DescrFromType(NPY_BOOL);
+        return descr;
+    }
+    if (PyLong_CheckExact(arg)) {
+        auto&& descr = PyArray_DescrFromType(NPY_INT32);
+        return descr;
+    }
+    if (PyFloat_CheckExact(arg)) {
+        auto&& descr = PyArray_DescrFromType(NPY_FLOAT32);
+        return descr;
+    }
+    return nullptr;
+}
+
+PyArray_Descr* _dtype_promotion(PyObject* const* args, size_t nargs) {
+    // Return value: New reference
+    SmallVector<PyArray_Descr*> tensors;
+    SmallVector<PyArray_Descr*> scalars;
+
+    bool is_tuple = false;
+    PyObject* tuple = nullptr;
+    if (nargs == 1 && (PyTuple_Check(args[0]) || PyList_Check(args[0]))) {
+        if (PyList_Check(args[0])) {
+            tuple = PyList_AsTuple(args[0]);
+        } else {
+            tuple = args[0];
+            Py_INCREF(tuple);
+        }
+        nargs = PyTuple_Size(tuple);
+        is_tuple = true;
+    }
+
+    for (size_t i = 0; i < nargs; ++i) {
+        PyObject* handle = is_tuple ? PyTuple_GetItem(tuple, i) : args[i];
+        if (handle == Py_None)
+            continue;
+        TensorWrapper* tw = TensorWrapper::try_cast(handle);
+        if (tw) {
+            mgb::DType type = tw->m_tensor->dtype();
+            auto&& descr = npy::dtype_mgb2np_descr(type);
+            Py_INCREF(descr.get());
+            tensors.emplace_back(descr.get());
+        } else {
+            if (PyArray_Check(handle) || PyArray_CheckScalar(handle)) {
+                auto&& descr = PyArray_DescrFromObject(handle, nullptr);
+                tensors.emplace_back(descr);
+                continue;
+            }
+
+            if (py::isinstance<PySymbolVar>(py::handle(handle))) {
+                auto var = py::handle(handle).cast<PySymbolVar*>();
+                mgb::DType type = var->m_node->dtype();
+                auto&& descr = npy::dtype_mgb2np_descr(type);
+                Py_INCREF(descr.get());
+                tensors.emplace_back(descr.get());
+                continue;
+            }
+
+            PyArray_Descr* descr = scalar2dtype(handle);
+            if (descr) {
+                scalars.emplace_back(descr);
+                continue;
+            }
+        }
+    }
+
+    auto max_pri_scalars = max_priority(scalars);
+    auto max_pri_tensors = max_priority(tensors);
+
+    if (max_pri_scalars <= 0 && max_pri_tensors <= 0) {
+        throw py::value_error("invalid input, no dtype avaliable");
+    }
+    PyArray_Descr* res;
+    if (max_pri_scalars > max_pri_tensors) {
+        res = promote_types(scalars, max_pri_scalars);
+    } else {
+        res = promote_types(tensors, max_pri_tensors);
+    }
+    for (auto* p : tensors) {
+        Py_DECREF(p);
+    }
+    for (auto* p : scalars) {
+        Py_DECREF(p);
+    }
+    Py_XDECREF(tuple);
+    return res;
+}
+
+CompNode _get_device(PyObject* const* args, size_t nargs) {
+    bool is_tuple = false;
+    PyObject* tuple = nullptr;
+    if (nargs == 1 && (PyTuple_Check(args[0]) || PyList_Check(args[0]))) {
+        if (PyList_Check(args[0])) {
+            tuple = PyList_AsTuple(args[0]);
+        } else {
+            tuple = args[0];
+            Py_INCREF(tuple);
+        }
+        nargs = PyTuple_Size(tuple);
+        is_tuple = true;
+    }
+    bool valid = false;
+    CompNode cn;
+    for (size_t i = 0; i < nargs; ++i) {
+        PyObject* handle = is_tuple ? PyTuple_GetItem(tuple, i) : args[i];
+        TensorWrapper* tw = TensorWrapper::try_cast(handle);
+
+        bool is_symvar = py::isinstance<PySymbolVar>(py::handle(handle));
+        if (tw || is_symvar) {
+            if (!valid) {
+                cn = tw ? tw->m_tensor->comp_node()
+                        : py::handle(handle).cast<PySymbolVar*>()->m_node->comp_node();
+                valid = true;
+            } else {
+                CompNode cn1 = tw ? tw->m_tensor->comp_node()
+                                  : py::handle(handle)
+                                               .cast<PySymbolVar*>()
+                                               ->m_node->comp_node();
+                if (cn1 != cn) {
+                    throw py::value_error(ssprintf(
+                            "ambiguous device: %s (from %s) vs %s (from %s)",
+                            cn.to_string().c_str(), cn.to_string_logical().c_str(),
+                            cn1.to_string().c_str(), cn1.to_string_logical().c_str()));
+                }
+            }
+        }
+    }
+    if (!valid) {
+        return CompNode::load(get_default_device());
+    }
+    Py_XDECREF(tuple);
+    return cn;
+}
+
+// Returns the dtype that would result from performing an arithmetic
+// operation on the provided input tensors and scalars.
+PyObject* dtype_promotion(PyObject* self, PyObject* const* args, size_t nargs) {
+    if (!nargs) {
+        PyErr_SetString(PyExc_TypeError, "empty input is not allowed");
+        return nullptr;
+    }
+    try {
+        PyArray_Descr* res = _dtype_promotion(args, nargs);
+        return py::cast(npy::dtype_np2mgb_descr(res)).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+PyObject* get_device(PyObject* self, PyObject* const* args, size_t nargs) {
+    if (!nargs) {
+        PyErr_SetString(PyExc_TypeError, "empty input is not allowed");
+        return nullptr;
+    }
+    try {
+        CompNode cn = _get_device(args, nargs);
+        return py::cast(cn).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
 bool is_scalar(PyObject* tensor) {
     if (py::isinstance<PySymbolVar>(py::handle(tensor))) {
         auto var = py::handle(tensor).cast<PySymbolVar*>();
@@ -147,7 +364,6 @@ py::object _Const(
                         "dmap_callback");
         if (dmap.ptr() != Py_None) {
             device_obj = dmap(device);
-            py::print(device_obj);
         } else {
             device_obj = py::cast(CompNode::load(device.cast<std::string>()));
         }
@@ -1072,6 +1288,92 @@ py::object _reshape_cpp(py::handle inp_hdl, py::handle args) {
     return ret[0];
 }
 
+mgb::DType _get_dtype(py::handle tensor) {
+    if (auto tw = TensorWrapper::try_cast(tensor.ptr())) {
+        return tw->m_tensor->dtype();
+    } else {
+        auto var = tensor.cast<PySymbolVar*>();
+        return var->m_node->dtype();
+    }
+}
+
+py::object _astype_cpp(py::handle tensor, py::handle dtype_hdl) {
+    PyArray_Descr* descr;
+    if (!PyArray_DescrConverter(dtype_hdl.ptr(), &descr)) {
+        throw py::value_error(ssprintf(
+                "can not convert to numpy.dtype from %s",
+                dtype_hdl.ptr()->ob_type->tp_name));
+    }
+    PyArray_Descr* cur = npy::dtype_mgb2np_descr(_get_dtype(tensor)).get();
+    if (!dtype_equal(cur, descr)) {
+        std::shared_ptr<OpDef> op = TypeCvt::make(npy::dtype_np2mgb_descr(descr));
+        py::object Op = py::cast(op);
+        std::vector<PyObject*> p;
+        p.resize(2);
+        p[0] = Op.ptr();
+        p[1] = tensor.ptr();
+        py::tuple ret =
+                py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
+        return ret[0];
+    } else {
+        return py::reinterpret_borrow<py::object>(tensor);
+    }
+}
+
+py::object _convert_single_value_cpp(
+        py::handle value, py::handle dtype, py::handle device) {
+    if (is_tensor_or_symbolvar(value)) {
+        if (_get_dtype(value).category() != DTypeCategory::QUANTIZED) {
+            return _astype_cpp(value, dtype);
+        }
+    } else {
+        return _Const(value, dtype, device, py::none());
+    }
+    return py::reinterpret_borrow<py::object>(value);
+}
+
+py::object _convert_inputs_cpp(
+        PyObject* const* args, size_t nargs, py::object dtype, py::object device) {
+    ComputingGraph* graph = nullptr;
+    py::handle typeobj;
+    py::list lis;
+    for (size_t i = 0; i < nargs; ++i) {
+        py::handle h = py::handle(args[i]);
+        lis.append(h);
+        if (py::isinstance<PySymbolVar>(h)) {
+            auto var = h.cast<PySymbolVar*>();
+            auto g = var->m_node->owner_graph();
+            if (!graph) {
+                graph = g;
+                typeobj = h.get_type();
+            } else {
+                mgb_assert(graph == g);
+            }
+        }
+    }
+    if (graph) {
+        CompNode cn = device.cast<CompNode>();
+        for (size_t i = 0; i < nargs; ++i) {
+            OperatorNodeConfig config(cn);
+            auto hv = npy::np2tensor(
+                    lis[i].ptr(), npy::Meth::borrow(cn), dtype.cast<mgb::DType>());
+            if (py::isinstance<PySymbolVar>(lis[i])) {
+                lis[i] = typeobj(opr::ImmutableTensor::make(*graph, hv, config).node());
+            }
+        }
+    }
+    auto convert = [&](py::object value) {
+        if (value.ptr() == Py_None) {
+            return value;
+        }
+        return _convert_single_value_cpp(value, dtype, device);
+    };
+    for (size_t i = 0; i < lis.size(); ++i) {
+        lis[i] = convert(lis[i]);
+    }
+    return py::reinterpret_steal<py::tuple>(PyList_AsTuple(lis.ptr()));
+}
+
 PyObject* make_shape_tuple(PyObject* self, PyObject* const* args, size_t nargs) {
     try {
         return _make_shape_tuple(py::handle(args[0])).release().ptr();
@@ -1152,4 +1454,38 @@ PyObject* Const(PyObject* self, PyObject* const* args, size_t nargs) {
     PYEXT17_TRANSLATE_EXC_RET(nullptr)
 }
 
+PyObject* astype_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        return _astype_cpp(py::handle(args[0]), py::handle(args[1])).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+PyObject* convert_single_value_cpp(
+        PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        return _convert_single_value_cpp(
+                       py::handle(args[0]), py::handle(args[1]), py::handle(args[2]))
+                .release()
+                .ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+PyObject* convert_inputs_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        py::object dtype = py::reinterpret_steal<py::object>(
+                dtype_promotion(self, args, nargs - 1));
+        py::object device;
+        if (args[nargs - 1] == Py_None) {
+            device = py::reinterpret_steal<py::object>(
+                    get_device(self, args, nargs - 1));
+        } else {
+            device = py::reinterpret_borrow<py::object>(args[nargs - 1]);
+        }
+        return _convert_inputs_cpp(args, nargs - 1, dtype, device).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
 }  // namespace mgb::imperative::python

imperative/python/src/tensor_utils.h

@@ -2,6 +2,10 @@
 
 namespace mgb::imperative::python {
 
+PyObject* dtype_promotion(PyObject* self, PyObject* const* args, size_t nargs);
+
+PyObject* get_device(PyObject* self, PyObject* const* args, size_t nargs);
+
 PyObject* make_shape_tuple(PyObject* self, PyObject* const* args, size_t nargs);
 
 PyObject* getitem_cpp(PyObject* self, PyObject* const* args, size_t nargs);
@@ -22,4 +26,10 @@ PyObject* reshape_cpp(PyObject* self, PyObject* const* args, size_t nargs);
 
 PyObject* Const(PyObject* self, PyObject* const* args, size_t nargs);
 
+PyObject* astype_cpp(PyObject* self, PyObject* const* args, size_t nargs);
+
+PyObject* convert_single_value_cpp(PyObject* self, PyObject* const* args, size_t nargs);
+
+PyObject* convert_inputs_cpp(PyObject* self, PyObject* const* args, size_t nargs);
+
 }  // namespace mgb::imperative::python
\ No newline at end of file