ENH: core: Fix up coercion rules for half/float16

4 files changed, 46 insertions, 19 deletions

diff --git a/numpy/core/src/multiarray/convert_datatype.c b/numpy/core/src/multiarray/convert_datatype.c
index d2aaf054f..0040e8ad5 100644
--- a/numpy/core/src/multiarray/convert_datatype.c
+++ b/numpy/core/src/multiarray/convert_datatype.c
@@ -567,7 +567,6 @@ PyArray_CanCastSafely(int fromtype, int totype)
             }
         }
     }
-
     return 0;
 }
 
diff --git a/numpy/core/src/multiarray/scalartypes.c.src b/numpy/core/src/multiarray/scalartypes.c.src
index 0ac374fd5..c66337602 100644
--- a/numpy/core/src/multiarray/scalartypes.c.src
+++ b/numpy/core/src/multiarray/scalartypes.c.src
@@ -3297,10 +3297,10 @@ initialize_casting_tables(void)
     /* Compile-time loop of scalar kinds */
 /**begin repeat
  * #NAME = BOOL, BYTE, UBYTE, SHORT, USHORT, INT, UINT, LONG, ULONG,
- *         LONGLONG, ULONGLONG, FLOAT, DOUBLE, LONGDOUBLE,
+ *         LONGLONG, ULONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE,
  *         CFLOAT, CDOUBLE, CLONGDOUBLE#
- * #SCKIND = BOOL, (INTNEG, INTPOS)*5, FLOAT, FLOAT, FLOAT,
- *           COMPLEX, COMPLEX, COMPLEX#
+ * #SCKIND = BOOL, (INTNEG, INTPOS)*5, FLOAT*4,
+ *           COMPLEX*3#
  */
     _npy_scalar_kinds_table[PyArray_@NAME@] = PyArray_@SCKIND@_SCALAR;
 /**end repeat**/
@@ -3330,22 +3330,22 @@ initialize_casting_tables(void)
     /* Compile-time loop of casting rules */
 /**begin repeat
  * #FROM_NAME = BYTE, UBYTE, SHORT, USHORT, INT, UINT, LONG, ULONG,
- *              LONGLONG, ULONGLONG, FLOAT, DOUBLE, LONGDOUBLE,
+ *              LONGLONG, ULONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE,
  *              CFLOAT, CDOUBLE, CLONGDOUBLE#
  * #FROM_BASENAME = BYTE, BYTE, SHORT, SHORT, INT, INT, LONG, LONG,
- *                  LONGLONG, LONGLONG, FLOAT, DOUBLE, LONGDOUBLE,
+ *                  LONGLONG, LONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE,
  *                  FLOAT, DOUBLE, LONGDOUBLE#
  * #from_isint = 1, 0, 1, 0, 1, 0, 1, 0,
- *               1, 0, 0, 0, 0,
+ *               1, 0, 0, 0, 0, 0,
  *               0, 0, 0#
  * #from_isuint = 0, 1, 0, 1, 0, 1, 0, 1,
- *                0, 1, 0, 0, 0,
+ *                0, 1, 0, 0, 0, 0,
  *                0, 0, 0#
  * #from_isfloat = 0, 0, 0, 0, 0, 0, 0, 0,
- *                 0, 0, 1, 1, 1,
+ *                 0, 0, 1, 1, 1, 1,
  *                 0, 0, 0#
  * #from_iscomplex = 0, 0, 0, 0, 0, 0, 0, 0,
- *                   0, 0, 0, 0, 0,
+ *                   0, 0, 0, 0, 0, 0,
  *                   1, 1, 1#
  */
 #define _FROM_BSIZE NPY_SIZEOF_@FROM_BASENAME@
@@ -3356,22 +3356,22 @@ initialize_casting_tables(void)
 
 /**begin repeat1
  * #TO_NAME = BYTE, UBYTE, SHORT, USHORT, INT, UINT, LONG, ULONG,
- *            LONGLONG, ULONGLONG, FLOAT, DOUBLE, LONGDOUBLE,
+ *            LONGLONG, ULONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE,
  *            CFLOAT, CDOUBLE, CLONGDOUBLE#
  * #TO_BASENAME = BYTE, BYTE, SHORT, SHORT, INT, INT, LONG, LONG,
- *                LONGLONG, LONGLONG, FLOAT, DOUBLE, LONGDOUBLE,
+ *                LONGLONG, LONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE,
  *                FLOAT, DOUBLE, LONGDOUBLE#
  * #to_isint = 1, 0, 1, 0, 1, 0, 1, 0,
- *             1, 0, 0, 0, 0,
+ *             1, 0, 0, 0, 0, 0,
  *             0, 0, 0#
  * #to_isuint = 0, 1, 0, 1, 0, 1, 0, 1,
- *              0, 1, 0, 0, 0,
+ *              0, 1, 0, 0, 0, 0,
  *              0, 0, 0#
  * #to_isfloat = 0, 0, 0, 0, 0, 0, 0, 0,
- *               0, 0, 1, 1, 1,
+ *               0, 0, 1, 1, 1, 1,
  *               0, 0, 0#
  * #to_iscomplex = 0, 0, 0, 0, 0, 0, 0, 0,
- *                 0, 0, 0, 0, 0,
+ *                 0, 0, 0, 0, 0, 0,
  *                 1, 1, 1#
  */
 #define _TO_BSIZE NPY_SIZEOF_@TO_BASENAME@
diff --git a/numpy/core/src/umath/ufunc_object.c b/numpy/core/src/umath/ufunc_object.c
index be38a9f10..39b04db73 100644
--- a/numpy/core/src/umath/ufunc_object.c
+++ b/numpy/core/src/umath/ufunc_object.c
@@ -224,10 +224,11 @@ _lowest_type(char intype)
     case PyArray_ULONG:
     case PyArray_ULONGLONG:
         return PyArray_UBYTE;
-    /* case PyArray_FLOAT:*/
+    /* case PyArray_HALF: */
+    case PyArray_FLOAT:
     case PyArray_DOUBLE:
     case PyArray_LONGDOUBLE:
-        return PyArray_FLOAT;
+        return PyArray_HALF;
     /* case PyArray_CFLOAT:*/
     case PyArray_CDOUBLE:
     case PyArray_CLONGDOUBLE:
@@ -3328,7 +3329,7 @@ PyUFunc_GenericReduction(PyUFuncObject *self, PyObject *args,
          * is used for add and multiply reduction to avoid overflow
          */
         int typenum = PyArray_TYPE(mp);
-        if ((typenum < NPY_FLOAT)
+        if ((typenum < NPY_HALF)
             && ((strcmp(self->name,"add") == 0)
                 || (strcmp(self->name,"multiply") == 0))) {
             if (PyTypeNum_ISBOOL(typenum)) {
diff --git a/numpy/core/tests/test_half.py b/numpy/core/tests/test_half.py
index 4d61bc28f..5a547d35e 100644
--- a/numpy/core/tests/test_half.py
+++ b/numpy/core/tests/test_half.py
@@ -276,3 +276,30 @@ def test_half_ufuncs():
     assert_equal(np.frexp(b), ([-0.5,0.625,0.5,0.5,0.75],[2,3,1,3,2]))
     assert_equal(np.ldexp(b,[0,1,2,4,2]), [-2,10,4,64,12])
 
+def test_half_coercion():
+    """Test that half gets coerced properly with the other types"""
+    a16 = np.array((1,),dtype=float16)
+    a32 = np.array((1,),dtype=float32)
+    b16 = float16(1)
+    b32 = float32(1)
+
+    assert_equal(np.power(a16,2).dtype, float16)
+    assert_equal(np.power(a16,2.0).dtype, float16)
+    assert_equal(np.power(a16,b16).dtype, float16)
+    assert_equal(np.power(a16,b32).dtype, float16)
+    assert_equal(np.power(a16,a16).dtype, float16)
+    assert_equal(np.power(a16,a32).dtype, float32)
+
+    assert_equal(np.power(b16,2).dtype, float64)
+    assert_equal(np.power(b16,2.0).dtype, float64)
+    assert_equal(np.power(b16,b16).dtype, float16)
+    assert_equal(np.power(b16,b32).dtype, float32)
+    assert_equal(np.power(b16,a16).dtype, float16)
+    assert_equal(np.power(b16,a32).dtype, float32)
+
+    assert_equal(np.power(a32,a16).dtype, float32)
+    assert_equal(np.power(a32,b16).dtype, float32)
+    assert_equal(np.power(b32,a16).dtype, float16)
+    assert_equal(np.power(b32,b16).dtype, float32)
+
+