223 lines
5.1 KiB
C
223 lines
5.1 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_vlog_f16.c
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* Description: Fast vectorized log
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "dsp/fast_math_functions_f16.h"
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#include "dsp/support_functions_f16.h"
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#if defined(ARM_FLOAT16_SUPPORTED)
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/* Degree of the polynomial approximation */
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#define NB_DEG_LOGF16 3
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/*
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Related to the Log2 of the number of approximations.
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For instance, with 3 there are 1 + 2^3 polynomials
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*/
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#define NB_DIV_LOGF16 3
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/* Length of the LUT table */
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#define NB_LUT_LOGF16 (NB_DEG_LOGF16+1)*(1 + (1<<NB_DIV_LOGF16))
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/*
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LUT of polynomial approximations.
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Could be generated with:
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ClearAll[lut, coefs, nb, deg];
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nb = 3;
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deg = 3;
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lut = Table[
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MiniMaxApproximation[
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Log[x/2^nb + i], {x, {10^-6, 1.0/2^nb}, deg, 0},
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MaxIterations -> 1000][[2, 1]], {i, 1, 2, (1.0/2^nb)}];
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coefs = Chop@Flatten[CoefficientList[lut, x]];
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*/
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static float16_t lut_logf16[NB_LUT_LOGF16]={
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0,0.125,-0.00781197,0.00063974,0.117783,
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0.111111,-0.00617212,0.000447935,0.223144,
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0.1,-0.00499952,0.000327193,0.318454,0.0909091,
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-0.00413191,0.000246234,0.405465,0.0833333,
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-0.00347199,0.000189928,0.485508,0.0769231,
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-0.00295841,0.00014956,0.559616,0.0714286,
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-0.0025509,0.000119868,0.628609,0.0666667,
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-0.00222213,0.0000975436,0.693147,
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0.0625,-0.00195305,0.0000804357};
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float16_t logf16_scalar(float16_t x)
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{
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int16_t i = arm_typecast_s16_f16(x);
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int32_t vecExpUnBiased = (i >> 10) - 15;
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i = i - (vecExpUnBiased << 10);
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float16_t vecTmpFlt1 = arm_typecast_f16_s16(i);
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float16_t *lut;
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int n;
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float16_t tmp,v;
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tmp = ((_Float16)vecTmpFlt1 - 1.0f16) * (1 << NB_DIV_LOGF16);
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n = (int)floor((double)tmp);
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v = (_Float16)tmp - (_Float16)n;
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lut = lut_logf16 + n * (1+NB_DEG_LOGF16);
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float16_t res = lut[NB_DEG_LOGF16-1];
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for(int j=NB_DEG_LOGF16-2; j >=0 ; j--)
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{
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res = (_Float16)lut[j] + (_Float16)v * (_Float16)res;
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}
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res = (_Float16)res + 0.693147f16 * (_Float16)vecExpUnBiased;
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return(res);
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}
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#if defined(ARM_MATH_MVE_FLOAT16) && !defined(ARM_MATH_AUTOVECTORIZE)
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#include "arm_common_tables.h"
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#include "arm_vec_math_f16.h"
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float16x8_t vlogq_lut_f16(float16x8_t vecIn)
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{
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int16x8_t i = vreinterpretq_s16_f16(vecIn);
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int16x8_t vecExpUnBiased = vsubq_n_s16(vshrq_n_s16(i,10), 15);
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i = vsubq_s16(i,vshlq_n_s16(vecExpUnBiased,10));
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float16x8_t vecTmpFlt1 = vreinterpretq_f16_s16(i);
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float16x8_t lutV;
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int16x8_t n;
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int16x8_t offset;
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float16x8_t tmp,v,res;
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tmp = vmulq_n_f16(vsubq_n_f16(vecTmpFlt1,1.0f16),(_Float16)(1 << NB_DIV_LOGF16));
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n = vcvtq_s16_f16(tmp);
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v = vsubq_f16(tmp,vcvtq_f16_s16(n));
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offset = vmulq_n_s16(n,(1+NB_DEG_LOGF16));
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offset = vaddq_n_s16(offset,NB_DEG_LOGF16-1);
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res = vldrhq_gather_shifted_offset_f16(lut_logf16,(uint16x8_t)offset);
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offset = vsubq_n_s16(offset,1);
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for(int j=NB_DEG_LOGF16-2; j >=0 ; j--)
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{
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lutV = vldrhq_gather_shifted_offset_f16(lut_logf16,(uint16x8_t)offset);
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res = vfmaq_f16(lutV,v,res);
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offset = vsubq_n_s16(offset,1);
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}
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res = vfmaq_n_f16(res,vcvtq_f16_s16(vecExpUnBiased),0.693147f16);
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return(res);
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}
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#endif
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/**
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@ingroup groupFastMath
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*/
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/**
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@addtogroup vlog
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@{
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*/
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/**
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@brief Floating-point vector of log values.
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@param[in] pSrc points to the input vector
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@param[out] pDst points to the output vector
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@param[in] blockSize number of samples in each vector
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@return none
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*/
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void arm_vlog_f16(
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const float16_t * pSrc,
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float16_t * pDst,
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uint32_t blockSize)
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{
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uint32_t blkCnt;
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#if defined(ARM_MATH_MVE_FLOAT16) && !defined(ARM_MATH_AUTOVECTORIZE)
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f16x8_t src;
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f16x8_t dst;
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blkCnt = blockSize >> 3;
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while (blkCnt > 0U)
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{
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src = vld1q(pSrc);
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dst = vlogq_lut_f16(src);
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vst1q(pDst, dst);
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pSrc += 8;
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pDst += 8;
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/* Decrement loop counter */
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blkCnt--;
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}
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blkCnt = blockSize & 7;
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#else
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blkCnt = blockSize;
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#endif
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while (blkCnt > 0U)
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{
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/* C = log(A) */
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/* Calculate log and store result in destination buffer. */
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*pDst++ = logf16_scalar(*pSrc++);
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/* Decrement loop counter */
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blkCnt--;
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}
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}
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/**
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@} end of vlog group
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*/
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#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */
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