Implement signbit ufunc

Author: juntyr

quaddtype/numpy_quaddtype/src/ops.hpp

@@ -20,11 +20,24 @@ quad_positive(Sleef_quad *op)
 static inline Sleef_quad
 quad_sign(Sleef_quad *op)
 {
-    int32_t sign = Sleef_icmpq1(*op, Sleef_cast_from_doubleq1(0.0));
+    Sleef_quad zero = Sleef_cast_from_doubleq1(0.0);
+    int32_t sign = Sleef_icmpq1(*op, zero);
     // sign(x=NaN) = x; otherwise sign(x) in { -1.0; 0.0; +1.0 }
     return Sleef_iunordq1(*op, *op) ? *op : Sleef_cast_from_int64q1(sign);
 }
 
+static inline int32_t
+quad_signbit(Sleef_quad *op)
+{
+    // FIXME @juntyr or @SwayamInSync: replace with binary implementation
+    //  once we test big and little endian in CI
+    Sleef_quad zero = Sleef_cast_from_doubleq1(0.0);
+    Sleef_quad one = Sleef_cast_from_doubleq1(1.0);
+    Sleef_quad one_signed = Sleef_copysignq1(one, *op);
+    // signbit(x) = 1 iff copysign(1, x) == -1
+    return Sleef_icmpltq1(one_signed, zero);
+}
+
 static inline Sleef_quad
 quad_absolute(Sleef_quad *op)
 {
@@ -170,6 +183,12 @@ ld_sign(long double *op)
     return *op;
 }
 
+static inline int32_t
+ld_signbit(long double *op)
+{
+    return signbit(*op);
+}
+
 static inline long double
 ld_rint(long double *op)
 {

quaddtype/numpy_quaddtype/src/umath.cpp

@@ -214,6 +214,9 @@ init_quad_unary_ops(PyObject *numpy)
     if (create_quad_unary_ufunc<quad_sign, ld_sign>(numpy, "sign") < 0) {
         return -1;
     }
+    if (create_quad_unary_ufunc<quad_signbit, ld_signbit>(numpy, "signbit") < 0) {
+        return -1;
+    }
     if (create_quad_unary_ufunc<quad_rint, ld_rint>(numpy, "rint") < 0) {
         return -1;
     }

quaddtype/tests/test_quaddtype.py

@@ -107,7 +107,7 @@ def test_array_aminmax(op, a, b):
         assert np.all((quad_res == float_res) | ((quad_res != quad_res) & (float_res != float_res)))
 
 
-@pytest.mark.parametrize("op,nop", [("neg", "negative"), ("pos", "positive"), ("abs", "absolute"), (None, "sign")])
+@pytest.mark.parametrize("op,nop", [("neg", "negative"), ("pos", "positive"), ("abs", "absolute"), (None, "sign"), (None, "signbit")])
 @pytest.mark.parametrize("val", ["3.0", "-3.0", "12.5", "100.0", "0.0", "-0.0", "inf", "-inf", "nan", "-nan"])
 def test_unary_ops(op, nop, val):
     op_func = None if op is None else getattr(operator, op)
@@ -124,11 +124,12 @@ def test_unary_ops(op, nop, val):
         float_result = op_func(float_val)
 
         # FIXME: @juntyr: replace with array_equal once isnan is supported
-        # FIXME: @juntyr: also check the signbit once that is supported
         with np.errstate(invalid="ignore"):
             assert (
                 (np.float64(quad_result) == float_result) or
                 ((float_result != float_result) and (quad_result != quad_result))
+            ) and (
+                np.signbit(float_result) == np.signbit(quad_result)
             ), f"{op}({val}) should be {float_result}, but got {quad_result}"