Reimplement erf function

* The current implementation has signfinicant inaccuracy
  and the issue cascades to GELU.
* Use the implementation from Arm® Optimized Routines.
  The maximum error is 1.93 ULP.

Resolves: COMPMID-6554
Signed-off-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Change-Id: If80131e164b7a078e34dd8e05b1506698f31d17a
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/10395
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: TeresaARM <teresa.charlinreyes@arm.com>
Reviewed-by: SiCong Li <sicong.li@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/src/core/utils/Math.h b/src/core/utils/Math.h
new file mode 100644
index 0000000000..f006948f69
--- /dev/null
+++ b/src/core/utils/Math.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2023 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef ACL_SRC_CORE_UTILS_MATH_H
+#define ACL_SRC_CORE_UTILS_MATH_H
+
+#include <array>
+
+namespace arm_compute
+{
+
+/** Lookup table for erf(x) calculation. */
+template <typename T>
+struct ErfLutEntry
+{
+    /** erf(x) */
+    T value;
+
+    /** 2 / sqrt(pi) * e^(-x^2) */
+    T scale;
+};
+
+/** The lookup table for FP32 erf(x) calculation. */
+extern const std::array<ErfLutEntry<float>, 513> erf_f32_lut;
+
+} // namespace arm_compute
+
+#endif // ACL_SRC_CORE_UTILS_MATH_H