Revise type coercion

cunumeric/_ufunc/ufunc.py

@@ -13,12 +13,12 @@
 # limitations under the License.
 #
 
+import numpy as np
 from cunumeric.array import (
     broadcast_shapes,
     convert_to_cunumeric_ndarray,
     ndarray,
 )
-from numpy import can_cast as np_can_cast, dtype as np_dtype
 
 _UNARY_DOCSTRING_TEMPLATE = """{}
 
@@ -132,7 +132,7 @@ def _maybe_cast_input(self, arr, to_dtype, casting):
         if arr.dtype == to_dtype:
             return arr
 
-        if not np_can_cast(arr.dtype, to_dtype, casting=casting):
+        if not np.can_cast(arr.dtype, to_dtype, casting=casting):
             raise TypeError(
                 f"Cannot cast ufunc '{self._name}' input from "
                 f"{arr.dtype} to {to_dtype} with casting rule '{casting}'"
@@ -168,17 +168,17 @@ def ntypes(self):
 
     def _resolve_dtype(self, arr, casting, precision_fixed):
         if arr.dtype.char in self._types:
-            return arr, np_dtype(self._types[arr.dtype.char])
+            return arr, np.dtype(self._types[arr.dtype.char])
 
         if arr.dtype in self._resolution_cache:
             to_dtype = self._resolution_cache[arr.dtype]
             arr = arr.astype(to_dtype)
-            return arr, np_dtype(self._types[to_dtype.char])
+            return arr, np.dtype(self._types[to_dtype.char])
 
         chosen = None
         if not precision_fixed:
             for in_ty in self._types.keys():
-                if np_can_cast(arr.dtype, in_ty):
+                if np.can_cast(arr.dtype, in_ty):
                     chosen = in_ty
                     break
 
@@ -188,10 +188,10 @@ def _resolve_dtype(self, arr, casting, precision_fixed):
                 "for the given casting"
             )
 
-        to_dtype = np_dtype(chosen)
+        to_dtype = np.dtype(chosen)
         self._resolution_cache[arr.dtype] = to_dtype
 
-        return arr.astype(to_dtype), np_dtype(self._types[to_dtype.char])
+        return arr.astype(to_dtype), np.dtype(self._types[to_dtype.char])
 
     def __call__(
         self,
@@ -244,7 +244,7 @@ def __call__(
             out = result
         else:
             if out.dtype != res_dtype:
-                if not np_can_cast(res_dtype, out.dtype, casting=casting):
+                if not np.can_cast(res_dtype, out.dtype, casting=casting):
                     raise TypeError(
                         f"Cannot cast ufunc '{self._name}' output from "
                         f"{res_dtype} to {out.dtype} with casting rule "
@@ -296,26 +296,56 @@ def types(self):
     def ntypes(self):
         return len(self._types)
 
-    def _resolve_dtype(self, arrs, casting, precision_fixed):
-        common_dtype = ndarray.find_common_type(*arrs)
+    @staticmethod
+    def _find_common_type(arrs, orig_args):
+        # FIXME: The following is a miserable attempt to implement type
+        # coercion rules that try to match NumPy's rules for a subset of cases;
+        # for the others, cuNumeric computes a type different from what
+        # NumPy produces for the same operands. Type coercion rules shouldn't
+        # be this difficult to imitate...
+
+        all_scalars = all(arr.ndim == 0 for arr in arrs)
+        all_arrays = all(arr.ndim > 0 for arr in arrs)
+        kinds = set(arr.dtype.kind for arr in arrs)
+        lossy_conversion = ("i" in kinds or "u" in kinds) and (
+            "f" in kinds or "c" in kinds
+        )
+        use_min_scalar = not (all_scalars or all_arrays or lossy_conversion)
+
+        scalar_types = []
+        array_types = []
+        for arr, orig_arg in zip(arrs, orig_args):
+            if arr.ndim == 0:
+                scalar_types.append(
+                    np.dtype(np.min_scalar_type(orig_arg))
+                    if use_min_scalar
+                    else arr.dtype
+                )
+            else:
+                array_types.append(arr.dtype)
+
+        return np.find_common_type(array_types, scalar_types)
+
+    def _resolve_dtype(self, arrs, orig_args, casting, precision_fixed):
+        common_dtype = self._find_common_type(arrs, orig_args)
 
         key = (common_dtype.char, common_dtype.char)
         if key in self._types:
             arrs = [arr.astype(common_dtype) for arr in arrs]
-            return arrs, np_dtype(self._types[key])
+            return arrs, np.dtype(self._types[key])
 
         if key in self._resolution_cache:
             to_dtypes = self._resolution_cache[key]
             arrs = [
                 arr.astype(to_dtype) for arr, to_dtype in zip(arrs, to_dtypes)
             ]
-            return arrs, np_dtype(self._types[to_dtypes])
+            return arrs, np.dtype(self._types[to_dtypes])
 
         chosen = None
         if not precision_fixed:
             for in_dtypes in self._types.keys():
                 if all(
-                    np_can_cast(arr.dtype, to_dtype)
+                    np.can_cast(arr.dtype, to_dtype)
                     for arr, to_dtype in zip(arrs, in_dtypes)
                 ):
                     chosen = in_dtypes
@@ -330,7 +360,7 @@ def _resolve_dtype(self, arrs, casting, precision_fixed):
         self._resolution_cache[key] = chosen
         arrs = [arr.astype(to_dtype) for arr, to_dtype in zip(arrs, chosen)]
 
-        return arrs, np_dtype(self._types[chosen])
+        return arrs, np.dtype(self._types[chosen])
 
     def __call__(
         self,
@@ -343,7 +373,8 @@ def __call__(
         dtype=None,
         **kwargs,
     ):
-        arrs = [convert_to_cunumeric_ndarray(arr) for arr in (x1, x2)]
+        orig_args = (x1, x2)
+        arrs = [convert_to_cunumeric_ndarray(arr) for arr in orig_args]
 
         if out is not None:
             if isinstance(out, tuple):
@@ -384,7 +415,9 @@ def __call__(
         # Resolve the dtype to use for the computation and cast the input
         # if necessary. If the dtype is already fixed by the caller,
         # the dtype must be one of the dtypes supported by this operation.
-        arrs, res_dtype = self._resolve_dtype(arrs, casting, precision_fixed)
+        arrs, res_dtype = self._resolve_dtype(
+            arrs, orig_args, casting, precision_fixed
+        )
 
         if out is None:
             result = ndarray(
@@ -393,7 +426,7 @@ def __call__(
             out = result
         else:
             if out.dtype != res_dtype:
-                if not np_can_cast(res_dtype, out.dtype, casting=casting):
+                if not np.can_cast(res_dtype, out.dtype, casting=casting):
                     raise TypeError(
                         f"Cannot cast ufunc '{self._name}' output from "
                         f"{res_dtype} to {out.dtype} with casting rule "

tests/binary_op_typing.py

@@ -0,0 +1,134 @@
+# Copyright 2021-2022 NVIDIA Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from itertools import product
+
+import numpy as np
+
+import cunumeric as num
+
+
+def value_type(obj):
+    if np.isscalar(obj):
+        return "scalar"
+    elif obj.ndim == 0:
+        return f"{obj.dtype} 0d array"
+    else:
+        return f"{obj.dtype} array"
+
+
+def test(lhs_np, rhs_np, lhs_num, rhs_num):
+    print(f"{value_type(lhs_np)} x {value_type(rhs_np)}")
+
+    out_np = np.add(lhs_np, rhs_np)
+    out_num = num.add(lhs_num, rhs_num)
+
+    if out_np.dtype != out_num.dtype:
+        print("LHS")
+        print(lhs_np)
+        print("RHS")
+        print(rhs_np)
+        print(f"NumPy type: {out_np.dtype}, cuNumeric type: {out_num.dtype}")
+        assert False
+
+
+def run_all_tests():
+    types = [
+        "b",
+        "B",
+        "h",
+        "H",
+        "i",
+        "I",
+        "l",
+        "L",
+        "q",
+        "Q",
+        "e",
+        "f",
+        "d",
+        "F",
+        "D",
+    ]
+    array_values = [[1]]
+    scalar_values = [1, -1, 1.0, 1e-50, 1j]
+
+    for idx, lhs_type in enumerate(types):
+        for rhs_type in types[idx:]:
+            for lhs_value, rhs_value in product(array_values, array_values):
+                lhs_np = np.array(lhs_value, dtype=lhs_type)
+                rhs_np = np.array(rhs_value, dtype=rhs_type)
+
+                lhs_num = num.array(lhs_np)
+                rhs_num = num.array(rhs_np)
+
+                test(lhs_np, rhs_np, lhs_num, rhs_num)
+
+            for lhs_value, rhs_value in product(scalar_values, scalar_values):
+                try:
+                    lhs_np = np.array(lhs_value, dtype=lhs_type)
+                    rhs_np = np.array(rhs_value, dtype=rhs_type)
+
+                    lhs_num = num.array(lhs_np)
+                    rhs_num = num.array(rhs_np)
+
+                    test(lhs_np, rhs_np, lhs_num, rhs_num)
+                except TypeError:
+                    pass
+
+    for ty in types:
+        for array, scalar in product(array_values, scalar_values):
+            array_np = np.array(array, dtype=ty)
+            array_num = num.array(array_np)
+
+            test(array_np, scalar, array_num, scalar)
+
+    # TODO: NumPy's type coercion rules are confusing at best and impossible
+    # for any human being to understand in my opinion. My attempt to make
+    # sense of it for the past two days failed miserably. I managed to make
+    # the code somewhat compatible with NumPy for cases where Python scalars
+    # are passed.
+    #
+    # If anyone can do a better job than me and finally make cuNumeric
+    # implement the same typing rules, please put these tests back.
+    #
+    # for idx, lhs_type in enumerate(types):
+    #    for rhs_type in types[idx:]:
+    #        for array, scalar in product(array_values, scalar_values):
+    #            try:
+    #                lhs_np = np.array(array, dtype=lhs_type)
+    #                rhs_np = np.array(scalar, dtype=rhs_type)
+
+    #                lhs_num = num.array(lhs_np)
+    #                rhs_num = num.array(rhs_np)
+
+    #                test(lhs_np, rhs_np, lhs_num, rhs_num)
+    #            except TypeError:
+    #                pass
+
+    #            try:
+    #                lhs_np = np.array(scalar, dtype=lhs_type)
+    #                rhs_np = np.array(array, dtype=rhs_type)
+
+    #                lhs_num = num.array(lhs_np)
+    #                rhs_num = num.array(rhs_np)
+
+    #                test(lhs_np, rhs_np, lhs_num, rhs_num)
+    #            except TypeError:
+    #                pass
+
+
+if __name__ == "__main__":
+    run_all_tests()