feat(mge):add qint4/quint4 to python

GitOrigin-RevId: f94609db00fcaaa9ca249eb61639eb0482705f79

dnn/src/fallback/type_cvt/opr_impl.cpp

@@ -451,7 +451,12 @@ namespace fallback {
 
 void TypeCvtImpl::exec(_megdnn_tensor_in src, _megdnn_tensor_out dst) {
     check_exec(src.layout, dst.layout);
-    if (src.layout.is_contiguous() && dst.layout.is_contiguous()) {
+    auto is_quantize_lowbit = [](const DType& dt) {
+        return dt.category() == DTypeCategory::QUANTIZED && dt.is_low_bit();
+    };
+    if (src.layout.is_contiguous() && dst.layout.is_contiguous() &&
+        !is_quantize_lowbit(src.layout.dtype) &&
+        !is_quantize_lowbit(dst.layout.dtype)) {
         MEGDNN_DISPATCH_CPU_KERN_OPR(run_contiguous(src, dst));
     } else {
         naive::TypeCvtImpl::exec(src, dst);

python_module/megengine/_internal/dtype.py

@@ -32,7 +32,7 @@ def get_scale(dtype):
 def get_zero_point(dtype):
     assert is_quantize(dtype)
     metadata = dtype.metadata["mgb_dtype"]
-    assert metadata["name"] == "Quantized8Asymm"
+    assert metadata["name"] in ("Quantized8Asymm", "Quantized4Asymm")
     return metadata["zero_point"]
 
 
@@ -79,6 +79,38 @@ def qint32(scale):
     )
 
 
+def quint4(scale, zero_point):
+    """
+    Consturct a quantized unsigned int4 data type with ``scale`` (float) and
+    ``zero_point`` (uint8). The real value represented by a quint4 data type is
+    float_val = scale * (uint4_val - zero_point)
+    """
+    int_zp = int(zero_point)
+    assert int_zp == zero_point, "zero_point should be an integer"
+    if int_zp < 0 or int_zp > 15:
+        raise ValueError("zero_point should be within [0, 15] for quint4")
+    return np.dtype(
+        np.uint8,
+        metadata={
+            "mgb_dtype": {
+                "name": "Quantized4Asymm",
+                "scale": float(scale),
+                "zero_point": int(zero_point),
+            }
+        },
+    )
+
+
+def qint4(scale):
+    """
+    Construct a quantized int4 data type with ``scale`` (float). The real value
+    represented by a qint4 data type is float_val = scale * int4_val
+    """
+    return np.dtype(
+        np.int8, metadata={"mgb_dtype": {"name": "QuantizedS4", "scale": float(scale)}}
+    )
+
+
 def convert_to_quint8(arr, q):
     """
     Quantize a float NumPy ndarray into a quint8 one with specified params.
@@ -177,3 +209,71 @@ def convert_from_qint32(arr):
     ), "arr should be a ndarray with qint8 dtype"
     scale = arr.dtype.metadata["mgb_dtype"]["scale"]
     return arr.astype(np.float32) * scale
+
+
+def convert_to_quint4(arr, q):
+    """
+    Quantize a float NumPy ndarray into a quint4 one with specified params.
+
+    :param arr: Input ndarray.
+    :type arr: :class:`np.ndarray`
+    :param q: Target data type, should be a quint4.
+    :type q: :class:`np.dtype`
+    """
+    assert isinstance(arr, np.ndarray)
+    assert (
+        "mgb_dtype" in q.metadata
+        and q.metadata["mgb_dtype"]["name"] == "Quantized4Asymm"
+    ), "q should be a quint4 dtype"
+    scale, zp = q.metadata["mgb_dtype"]["scale"], q.metadata["mgb_dtype"]["zero_point"]
+    return (np.round(arr / scale) + zp).clip(0, 15).astype(q)
+
+
+def convert_from_quint4(arr):
+    """
+    Dequantize a quint4 NumPy ndarray into a float one.
+
+    :param arr: Input ndarray.
+    """
+    assert isinstance(arr, np.ndarray)
+    assert (
+        "mgb_dtype" in arr.dtype.metadata
+        and arr.dtype.metadata["mgb_dtype"]["name"] == "Quantized4Asymm"
+    ), "arr should be a ndarray with quint4 dtype"
+    scale, zp = (
+        arr.dtype.metadata["mgb_dtype"]["scale"],
+        arr.dtype.metadata["mgb_dtype"]["zero_point"],
+    )
+    return (arr.astype(np.float32) - zp) * scale
+
+
+def convert_to_qint4(arr, q):
+    """
+    Quantize a float NumPy ndarray into a qint4 one with specified params.
+
+    :param arr: Input ndarray.
+    :type arr: :class:`np.ndarray`
+    :param q: Target data type, should be a qint4.
+    :type q: :class:`np.dtype`
+    """
+    assert isinstance(arr, np.ndarray)
+    assert (
+        "mgb_dtype" in q.metadata and q.metadata["mgb_dtype"]["name"] == "QuantizedS4"
+    ), "q should be a qint4 dtype"
+    scale = q.metadata["mgb_dtype"]["scale"]
+    return (np.round(arr / scale)).clip(-8, 7).astype(q)
+
+
+def convert_from_qint4(arr):
+    """
+    Dequantize a qint4 NumPy ndarray into a float one.
+
+    :param arr: Input ndarray.
+    """
+    assert isinstance(arr, np.ndarray)
+    assert (
+        "mgb_dtype" in arr.dtype.metadata
+        and arr.dtype.metadata["mgb_dtype"]["name"] == "QuantizedS4"
+    ), "arr should be a ndarray with qint4 dtype"
+    scale = arr.dtype.metadata["mgb_dtype"]["scale"]
+    return arr.astype(np.float32) * scale

python_module/src/cpp/python_helper.cpp

@@ -452,6 +452,23 @@ std::unique_ptr<PyArray_Descr, PyArrayDescrDeleter> dtype_mgb2np_descr(
                         {{"scale", PyFloat_FromDouble(param.scale)}});
                 break;
             }
+            case DTypeEnum::Quantized4Asymm: {
+                auto& param = dtype.param<dtype::Quantized4Asymm>();
+                type_descr = PyArray_DescrNewFromType(NPY_UINT8);
+                type_descr->metadata = build_mgb_dtype_dict(
+                        DTypeTrait<dtype::Quantized4Asymm>::name,
+                        {{"scale", PyFloat_FromDouble(param.scale)},
+                         {"zero_point", PyLong_FromLong(param.zero_point)}});
+                break;
+            }
+            case DTypeEnum::QuantizedS4: {
+                auto& param = dtype.param<dtype::QuantizedS4>();
+                type_descr = PyArray_DescrNewFromType(NPY_INT8);
+                type_descr->metadata = build_mgb_dtype_dict(
+                        DTypeTrait<dtype::QuantizedS4>::name,
+                        {{"scale", PyFloat_FromDouble(param.scale)}});
+                break;
+            }
             case DTypeEnum::QuantizedS32: {
                 auto& param = dtype.param<dtype::QuantizedS32>();
                 type_descr = PyArray_DescrNewFromType(NPY_INT32);
@@ -529,7 +546,29 @@ DType dtype_np2mgb_descr(PyArray_Descr* descr) {
                     static_cast<float>(PyFloat_AS_DOUBLE(scale_py)),
                     static_cast<uint8_t>(zero_point));
         }
-        if (dtype_name == "QuantizedS32" || dtype_name == "QuantizedS8") {
+        if (dtype_name == "Quantized4Asymm") {
+            PyObject* scale_py = PyDict_GetItemString(metadata, "scale");
+            PyObject* zero_point_py =
+                    PyDict_GetItemString(metadata, "zero_point");
+            mgb_assert(scale_py && zero_point_py,
+                       "Invalid Quantized4Asymm metadata: missing scale or "
+                       "zero_point.");
+            mgb_assert(
+                    PyFloat_Check(scale_py),
+                    "Invalid Quantized4Asymm metadata: scale should be float");
+            mgb_assert(PyLong_Check(zero_point_py),
+                       "Invalid Quantized4Asymm metadata: zero_point should be "
+                       "integer");
+            auto zero_point = PyLong_AS_LONG(zero_point_py);
+            mgb_assert(zero_point >= 0 && zero_point < 15,
+                       "Invalid Quantized4Asymm metadata: zero_point should be "
+                       "in [0, 15)");
+            return dtype::Quantized4Asymm(
+                    static_cast<float>(PyFloat_AS_DOUBLE(scale_py)),
+                    static_cast<uint8_t>(zero_point));
+        }
+        if (dtype_name == "QuantizedS32" || dtype_name == "QuantizedS8" ||
+            dtype_name == "QuantizedS4") {
             PyObject* scale_py = PyDict_GetItemString(metadata, "scale");
             mgb_assert(scale_py, "Invalid metadata: missing scale");
             mgb_assert(PyFloat_Check(scale_py),
@@ -537,8 +576,10 @@ DType dtype_np2mgb_descr(PyArray_Descr* descr) {
             float scale = static_cast<float>(PyFloat_AS_DOUBLE(scale_py));
             if (dtype_name == "QuantizedS32") {
                 return dtype::QuantizedS32(scale);
-            } else {
+            } else if (dtype_name == "QuantizedS8"){
                 return dtype::QuantizedS8(scale);
+            } else {
+                return dtype::QuantizedS4(scale);
             }
         }
         throw ConversionError(

src/core/impl/dtype.cpp

@@ -14,6 +14,7 @@
 #include "megbrain/exception.h"
 #include "megbrain/utils/metahelper.h"
 #include "megbrain/utils/arith_helper.h"
+#include "megdnn/dtype.h"
 
 #include <cmath>
 #include <cstring>
@@ -357,6 +358,52 @@ struct LowbitMemcpy<bits, true> {
         }
     }
 };
+
+template<typename DT>
+struct QuantizedLowbitTrait;
+
+template<>
+struct QuantizedLowbitTrait<dtype::Quantized4Asymm> {
+    static constexpr int8_t SHIFT = 0;
+};
+
+template<>
+struct QuantizedLowbitTrait<dtype::QuantizedS4> {
+    static constexpr int8_t SHIFT = 8;
+};
+
+template <typename DT, bool div_byte = (DTypeTrait<DT>::category ==
+                                        DTypeCategory::QUANTIZED) &&
+                                       (8 % DTypeTrait<DT>::low_bit == 0)>
+struct QuantizedLowbitMemcpy;
+
+template <typename DT>
+struct QuantizedLowbitMemcpy<DT, true> {
+    // cast with bits that 8 % bits == 0
+    static constexpr uint16_t bits = DTypeTrait<DT>::low_bit;
+    static constexpr uint8_t MASK = (1 << bits) - 1;
+    using Trait = QuantizedLowbitTrait<DT>;
+
+    static void byte2compact(void* dest_raw, const void* src_raw, size_t n) {
+        auto dest = static_cast<uint8_t*>(dest_raw);
+        auto src = static_cast<const int8_t*>(src_raw);
+        memset(dest, 0, divup<size_t>(n * bits, 8));
+        for (size_t i = 0; i < n; ++i) {
+            int8_t val = src[i] + Trait::SHIFT;
+            mgb_assert(val >= 0 && val < (1 << bits));
+            dest[i * bits / 8] |= val << (i * bits % 8);
+        }
+    }
+    static void compact2byte(void* dest_raw, const void* src_raw, size_t n) {
+        auto dest = static_cast<int8_t*>(dest_raw);
+        auto src = static_cast<const uint8_t*>(src_raw);
+        for (size_t i = 0; i < n; ++i) {
+            int8_t val = ((src[i * bits / 8] >> (i * bits % 8)) & MASK);
+            dest[i] = val - Trait::SHIFT;
+        }
+    }
+};
+
 } // anonymous namespace
 
 void mgb::lowbit_memcpy_byte2compact(
@@ -365,6 +412,11 @@ void mgb::lowbit_memcpy_byte2compact(
     if (dtype == mgb::dtype::name##bits()) \
         return LowbitMemcpy<bits>::byte2compact(dest, src, n);
     MEGDNN_FOREACH_LOWBIT_DTYPE(cb)
+#undef cb
+#define cb(dt) \
+    if (dtype.enumv() == DTypeTrait<dt>::enumv) \
+        return QuantizedLowbitMemcpy<dt>::byte2compact(dest, src, n);
+    MEGDNN_FOREACH_QUANTIZED_LOWBIT_DTYPE(cb)
 #undef cb
     mgb_throw(MegBrainError, "bad dtype for lowbit: %s", dtype.name());
 }
@@ -375,6 +427,11 @@ void mgb::lowbit_memcpy_compact2byte(
     if (dtype == mgb::dtype::name##bits()) \
         return LowbitMemcpy<bits>::compact2byte(dest, src, n);
     MEGDNN_FOREACH_LOWBIT_DTYPE(cb)
+#undef cb
+#define cb(dt) \
+    if (dtype.enumv() == DTypeTrait<dt>::enumv) \
+        return QuantizedLowbitMemcpy<dt>::compact2byte(dest, src, n);
+    MEGDNN_FOREACH_QUANTIZED_LOWBIT_DTYPE(cb)
 #undef cb
     mgb_throw(MegBrainError, "bad dtype for lowbit: %s", dtype.name());
 }