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/*
* Copyright (C) 2022 Arm Limited or its affiliates.
*
* 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_softmax_common_s8.c
* Description: Softmax with s8 input and output of s8 or s16.
*
* $Date: 17 March 2022
* $Revision: V.1.0.1
*
* Target Processor: Cortex-M processors
* -------------------------------------------------------------------- */
#include "arm_nnsupportfunctions.h"
#define ACCUM_BITS 12
/**
* @ingroup groupSupport
*/
/**
* @addtogroup Softmax
* @{
*/
/*
* Softmax function with s8 input and output of s8 or s16.
*
* Refer header file for details.
*
*/
void arm_nn_softmax_common_s8(const int8_t *input,
const int32_t num_rows,
const int32_t row_size,
const int32_t mult,
const int32_t shift,
const int32_t diff_min,
const bool int16_output,
void *output)
{
const int32_t mask = (1 << shift);
int32_t col = 0;
int32_t row_idx;
for (row_idx = 0; row_idx < num_rows; ++row_idx)
{
// Find the maximum value in order to ensure numerical stability
int8_t max = *input;
for (col = 1; col < row_size; ++col)
{
max = MAX(max, input[col]);
}
int32_t diff = 0;
int32_t sum = 0;
for (col = 0; col < row_size; ++col)
{
diff = input[col] - max;
if (diff >= diff_min)
{
sum += DIV_POW2(EXP_ON_NEG(MUL_SAT(diff * mask, mult)), ACCUM_BITS);
}
}
const int32_t headroom = __CLZ(sum);
const int32_t shifted_scale = ONE_OVER1((sum > 0 ? sum << headroom : 0) - (1 << 31));
int32_t bits_over_unit;
if (int16_output)
{
int16_t *output_s16 = (int16_t *)output + row_idx * row_size;
bits_over_unit = ACCUM_BITS - headroom + 15;
for (col = 0; col < row_size; ++col)
{
diff = input[col] - max;
if (diff >= diff_min)
{
const int32_t res =
DIV_POW2(MUL_SAT(shifted_scale, EXP_ON_NEG(MUL_SAT(diff * mask, mult))), bits_over_unit) +
NN_Q15_MIN;
output_s16[col] = (int16_t)CLAMP(res, (int32_t)NN_Q15_MAX, (int32_t)NN_Q15_MIN);
}
else
{
output_s16[col] = NN_Q15_MIN;
}
}
}
else
{
int8_t *output_s8 = (int8_t *)output + row_idx * row_size;
bits_over_unit = ACCUM_BITS - headroom + 23;
for (col = 0; col < row_size; ++col)
{
diff = input[col] - max;
if (diff >= diff_min)
{
const int32_t res =
DIV_POW2(MUL_SAT(shifted_scale, EXP_ON_NEG(MUL_SAT(diff * mask, mult))), bits_over_unit) +
NN_Q7_MIN;
output_s8[col] = (int8_t)CLAMP(res, (int32_t)NN_Q7_MAX, (int32_t)NN_Q7_MIN);
}
else
{
output_s8[col] = NN_Q7_MIN;
}
}
}
input += row_size;
}
}
/**
* @} end of NNBasicMath group
*/
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