Implement erf function as ufunc extension

Author: antonwolfy

dpnp/special/_erf.py

@@ -0,0 +1,115 @@
+# -*- coding: utf-8 -*-
+# *****************************************************************************
+# Copyright (c) 2025, Intel Corporation
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+# - Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.
+# - Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+# THE POSSIBILITY OF SUCH DAMAGE.
+# *****************************************************************************
+
+"""
+Interface of the Error functions
+
+Notes
+-----
+This module is a face or public interface file for the library
+it contains:
+ - Interface functions
+ - documentation for the functions
+
+"""
+
+import dpnp.backend.extensions.ufunc._ufunc_impl as ufi
+from dpnp.dpnp_algo.dpnp_elementwise_common import DPNPUnaryFunc
+
+__all__ = ["erf"]
+
+
+class DPNPErf(DPNPUnaryFunc):
+    """Class that implements a family of erf functions."""
+
+    def __init__(
+        self,
+        name,
+        result_type_resolver_fn,
+        unary_dp_impl_fn,
+        docs,
+    ):
+        super().__init__(
+            name,
+            result_type_resolver_fn,
+            unary_dp_impl_fn,
+            docs,
+        )
+
+    def __call__(self, x, out=None):
+        return super().__call__(x, out=out)
+
+
+_ERF_DOCSTRING = r"""
+Returns the error function of complex argument.
+
+It is defined as :math:`\frac{2}{\sqrt{\pi}} \int_{0}^{z} e^{-t^2} \, dt`.
+
+For full documentation refer to :obj:`scipy.special.erf`.
+
+Parameters
+----------
+x : {dpnp.ndarray, usm_ndarray}
+    Input array.
+out : {dpnp.ndarray, usm_ndarray}, optional
+    Optional output array for the function values.
+
+See Also
+--------
+:obj:`dpnp.special.erfc` : Complementary error function.
+:obj:`dpnp.special.erfinv` : Inverse of the error function.
+:obj:`dpnp.special.erfcinv` : Inverse of the complementary error function.
+:obj:`dpnp.special.erfcx` : Scaled complementary error function.
+:obj:`dpnp.special.erfi` : Imaginary error function.
+
+Notes
+-----
+The cumulative of the unit normal distribution is given by
+
+.. math::
+    \Phi(z) = \frac{1}{2} \left[
+        1 + \operatorname{erf} \left(
+            \frac{z}{\sqrt{2}}
+        \right)
+    \right]
+
+Examples
+--------
+>>> import dpnp as np
+>>> x = np.linspace(-3, 3, num=5)
+>>> np.special.erf(x)
+array([[-0.99997791, -0.96610515,  0.        ,  0.96610515,  0.99997791])
+
+"""
+
+erf = DPNPErf(
+    "erf",
+    ufi._erf_result_type,
+    ufi._erf,
+    _ERF_DOCSTRING,
+    # mkl_fn_to_call="_mkl_erf_to_call",
+    # mkl_impl_fn="_erf",
+)