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/*
* Copyright (C) 2010-2018 Arm Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* ----------------------------------------------------------------------
* Project: CMSIS NN Library
* Title: arm_nn_activations_q15.c
* Description: Q15 neural network activation function using direct table look-up
*
* $Date: 17. January 2018
* $Revision: V.1.0.0
*
* Target Processor: Cortex-M cores
*
* -------------------------------------------------------------------- */
#include "arm_math.h"
#include "arm_common_tables.h"
#include "arm_nnfunctions.h"
/**
* @ingroup groupNN
*/
/**
* @addtogroup Acti
* @{
*/
/**
* @brief Q15 neural network activation function using direct table look-up
* @param[in,out] data pointer to input
* @param[in] size number of elements
* @param[in] int_width bit-width of the integer part, assume to be smaller than 3
* @param[in] type type of activation functions
* @return none.
*
* @details
*
* This is the direct table look-up approach.
*
* Assume here the integer part of the fixed-point is <= 3.
* More than 3 just not making much sense, makes no difference with
* saturation followed by any of these activation functions.
*/
void arm_nn_activations_direct_q15(q15_t * data, uint16_t size, uint16_t int_width, arm_nn_activation_type type)
{
uint16_t i = size;
q15_t *pIn = data;
q15_t *pOut = data;
uint16_t shift_size = 8 + 3 - int_width;
uint32_t bit_mask = 0x7FF >> int_width;
uint32_t full_frac = bit_mask + 1;
const q15_t *lookup_table;
switch (type)
{
case ARM_SIGMOID:
lookup_table = sigmoidTable_q15;
break;
case ARM_TANH:
default:
lookup_table = tanhTable_q15;
break;
}
while (i)
{
q15_t out;
q15_t in = *pIn++;
q15_t frac = (uint32_t) in & bit_mask;
q15_t value = lookup_table[__USAT(in >> shift_size, 8)];
q15_t value2 = lookup_table[__USAT(1 + (in >> shift_size), 8)];
/* doing the interpolation here for better accuracy */
out = ((q31_t) (full_frac - frac) * value + (q31_t) value2 * frac) >> shift_size;
*pOut++ = out;
i--;
}
}
/**
* @} end of Acti group
*/
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