diff options
Diffstat (limited to 'pl/math/sv_erff_2u.c')
-rw-r--r-- | pl/math/sv_erff_2u.c | 90 |
1 files changed, 0 insertions, 90 deletions
diff --git a/pl/math/sv_erff_2u.c b/pl/math/sv_erff_2u.c deleted file mode 100644 index adeee798ee2e..000000000000 --- a/pl/math/sv_erff_2u.c +++ /dev/null @@ -1,90 +0,0 @@ -/* - * Single-precision vector erf(x) function. - * - * Copyright (c) 2023, Arm Limited. - * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception - */ - -#include "sv_math.h" -#include "pl_sig.h" -#include "pl_test.h" - -static const struct data -{ - float min, max, scale, shift, third; -} data = { - .min = 0x1.cp-7f, /* 1/64 - 1/512. */ - .max = 3.9375, /* 4 - 8/128. */ - .scale = 0x1.20dd76p+0f, /* 2/sqrt(pi). */ - .shift = 0x1p16f, - .third = 0x1.555556p-2f, /* 1/3. */ -}; - -#define SignMask (0x80000000) - -/* Single-precision implementation of vector erf(x). - Approximation based on series expansion near x rounded to - nearest multiple of 1/128. - Let d = x - r, and scale = 2 / sqrt(pi) * exp(-r^2). For x near r, - - erf(x) ~ erf(r) + scale * d * [1 - r * d - 1/3 * d^2] - - Values of erf(r) and scale are read from lookup tables. - For |x| < 0x1.cp-7, the algorithm sets r = 0, erf(r) = 0, and scale = 2 / - sqrt(pi), so it simply boils down to a Taylor series expansion near 0. For - |x| > 3.9375, erf(|x|) rounds to 1.0f. - - Maximum error on each interval: - - [0, 0x1.cp-7]: 1.93 ULP - _ZGVsMxv_erff(0x1.c373e6p-9) got 0x1.fd686cp-9 want 0x1.fd6868p-9 - - [0x1.cp-7, 4.0]: 1.26 ULP - _ZGVsMxv_erff(0x1.1d002ep+0) got 0x1.c4eb9ap-1 want 0x1.c4eb98p-1. */ -svfloat32_t SV_NAME_F1 (erf) (svfloat32_t x, const svbool_t pg) -{ - const struct data *dat = ptr_barrier (&data); - - /* |x| > 1/64 - 1/512. */ - svbool_t a_gt_min = svacgt (pg, x, dat->min); - - /* |x| >= 4.0 - 8/128. */ - svbool_t a_ge_max = svacge (pg, x, dat->max); - svfloat32_t a = svabs_x (pg, x); - - svfloat32_t shift = sv_f32 (dat->shift); - svfloat32_t z = svadd_x (pg, a, shift); - svuint32_t i - = svsub_x (pg, svreinterpret_u32 (z), svreinterpret_u32 (shift)); - - /* Saturate lookup index. */ - i = svsel (a_ge_max, sv_u32 (512), i); - - /* r and erf(r) set to 0 for |x| below min. */ - svfloat32_t r = svsub_z (a_gt_min, z, shift); - svfloat32_t erfr = svld1_gather_index (a_gt_min, __sv_erff_data.erf, i); - - /* scale set to 2/sqrt(pi) for |x| below min. */ - svfloat32_t scale = svld1_gather_index (a_gt_min, __sv_erff_data.scale, i); - scale = svsel (a_gt_min, scale, sv_f32 (dat->scale)); - - /* erf(x) ~ erf(r) + scale * d * (1 - r * d + 1/3 * d^2). */ - svfloat32_t d = svsub_x (pg, a, r); - svfloat32_t d2 = svmul_x (pg, d, d); - svfloat32_t y = svmla_x (pg, r, d, dat->third); - y = svmla_x (pg, erfr, scale, svmls_x (pg, d, d2, y)); - - /* Solves the |x| = inf case. */ - y = svsel (a_ge_max, sv_f32 (1.0f), y); - - /* Copy sign. */ - svuint32_t ix = svreinterpret_u32 (x); - svuint32_t iy = svreinterpret_u32 (y); - svuint32_t sign = svand_x (pg, ix, SignMask); - return svreinterpret_f32 (svorr_x (pg, sign, iy)); -} - -PL_SIG (SV, F, 1, erf, -4.0, 4.0) -PL_TEST_ULP (SV_NAME_F1 (erf), 1.43) -PL_TEST_SYM_INTERVAL (SV_NAME_F1 (erf), 0, 0x1.cp-7, 40000) -PL_TEST_SYM_INTERVAL (SV_NAME_F1 (erf), 0x1.cp-7, 3.9375, 40000) -PL_TEST_SYM_INTERVAL (SV_NAME_F1 (erf), 3.9375, inf, 40000) -PL_TEST_SYM_INTERVAL (SV_NAME_F1 (erf), 0, inf, 4000) |