Add dedicated sign handling for float16 dtype

Author: antonwolfy

dpnp/backend/kernels/elementwise_functions/spacing.hpp

@@ -51,8 +51,14 @@ struct SpacingFunctor
             return std::numeric_limits<resT>::quiet_NaN();
         }
 
-        const argT y = sycl::copysign(std::numeric_limits<argT>::infinity(), x);
-        return sycl::nextafter(x, y) - x;
+        constexpr argT inf = std::numeric_limits<argT>::infinity();
+        if constexpr (std::is_same_v<argT, sycl::half>) {
+            // numpy laways computes spacing towards +inf for float16 dtype
+            return sycl::nextafter(x, inf) - x;
+        }
+        else {
+            return sycl::nextafter(x, sycl::copysign(inf, x)) - x;
+        }
     }
 };
 } // namespace dpnp::kernels::spacing

tests/test_mathematical.py

@@ -1898,11 +1898,13 @@ def test_wrong_tol_type(self, xp, tol_val):
 
 
 class TestSpacing:
+    @pytest.mark.parametrize("sign", [1, -1])
     @pytest.mark.parametrize("dt", get_float_dtypes())
-    def test_basic(self, dt):
+    def test_basic(self, sign, dt):
         a = numpy.array(
-            [1, numpy.nan, numpy.inf, 0.0, 1e10, 1e-5, 1000, 10500], dtype=dt
+            [1, numpy.nan, numpy.inf, 1e10, 1e-5, 1000, 10500], dtype=dt
         )
+        a *= sign
         ia = dpnp.array(a)
 
         result = dpnp.spacing(ia)
@@ -1914,6 +1916,22 @@ def test_basic(self, dt):
         expected = numpy.spacing(-a)
         assert_equal(result, expected)
 
+    @pytest.mark.parametrize("dt", get_float_dtypes())
+    def test_zeros(self, dt):
+        a = numpy.array([0.0, -0.0], dtype=dt)
+        ia = dpnp.array(a)
+
+        result = dpnp.spacing(ia)
+        expected = numpy.spacing(a)
+        if numpy.lib.NumpyVersion(numpy.__version__) < "2.0.0":
+            assert_equal(result, expected)
+        else:
+            # numpy.spacing(-0.0) == numpy.spacing(0.0), i.e. NumPy returns
+            # positive value, while for any other negative input the result
+            # will be negative value (looks as a bug in NumPy)
+            expected[1] *= -1
+            assert_equal(result, expected)
+
     @pytest.mark.parametrize("dt", get_float_dtypes(no_float16=False))
     @pytest.mark.parametrize("val", [1, 1e-5, 1000])
     @pytest.mark.parametrize("xp", [numpy, dpnp])