xref: /aosp_15_r20/external/arm-optimized-routines/pl/math/tools/atanf.sollya (revision 412f47f9e737e10ed5cc46ec6a8d7fa2264f8a14)
1*412f47f9SXin Li// polynomial for approximating atanf(x)
2*412f47f9SXin Li//
3*412f47f9SXin Li// Copyright (c) 2022-2023, Arm Limited.
4*412f47f9SXin Li// SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
5*412f47f9SXin Li
6*412f47f9SXin Li// Generate list of monomials:
7*412f47f9SXin Li// Taylor series of atan is of the form x + ax^3 + bx^5 + cx^7 + ...
8*412f47f9SXin Li// So generate a, b, c, ... such that we can approximate atan(x) by:
9*412f47f9SXin Li// x + x^3 * (a + bx^2 + cx^4 + ...)
10*412f47f9SXin Li
11*412f47f9SXin Lideg = 7;
12*412f47f9SXin Li
13*412f47f9SXin Lia = 1.1754943508222875e-38;
14*412f47f9SXin Lib = 1;
15*412f47f9SXin Li
16*412f47f9SXin Lipoly = fpminimax((atan(sqrt(x))-sqrt(x))/x^(3/2), deg, [|single ...|], [a;b]);
17*412f47f9SXin Li
18*412f47f9SXin Lidisplay = hexadecimal;
19*412f47f9SXin Liprint("coeffs:");
20*412f47f9SXin Lifor i from 0 to deg do coeff(poly,i);
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