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/*
* Copyright (c) 2019 Arm Limited.
*
* SPDX-License-Identifier: MIT
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cmath>
#include <limits>
#include "qsymm8.hpp"
namespace qsymm8 {
#if(__ANDROID__ || BARE_METAL)
template <typename T> T round(T val) { return ::round(val); }
template <typename T> T exp2(T val) { return ::exp2(val); }
template <typename T> T log2(T val) { return ::log2(val); }
#else /* (__ANDROID__ || BARE_METAL) */
template <typename T> T round(T val) { return std::round(val); }
template <typename T> T exp2(T val) { return std::exp2(val); }
template <typename T> T log2(T val) { return std::log2(val); }
#endif /* (__ANDROID__ || BARE_METAL) */
// Symmetric quantization
int8_t QSymm8Params::quantize(float value) const
{
const float transformed = value / scale;
return static_cast<int8_t>(round(std::max(-128.0f, std::min(127.0f, transformed))));
}
float QSymm8Params::dequantize(const int8_t value) const
{
return scale * (static_cast<float>(value));
}
QSymm8RescaleParams QSymm8RescaleParams::make_rescale_params(
const QSymm8Params& weight_quant,
const QSymm8Params& input_quant,
const QSymm8Params& output_quant
)
{
// Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
const float rescale = weight_quant.scale * input_quant.scale / output_quant.scale;
const float shiftf = round(log2(0.5f / rescale));
const float multf = exp2(31.0f + shiftf)*rescale;
int64_t shift = static_cast<int64_t>(shiftf);
int64_t mult = static_cast<int64_t>(multf);
if (mult == (1ll << 31))
{
mult /= 2;
shift--;
}
assert(shift >= 0);
assert(mult <= std::numeric_limits<int32_t>::max());
return QSymm8RescaleParams(
static_cast<int32_t>(shift),
static_cast<int32_t>(mult),
rescale
);
}
QSymm8RescaleParams::QSymm8RescaleParams(int32_t shift, int32_t multi, float rescale)
: shift(shift), multiplier(multi), rescale(rescale)
{
}
// Symmetric per-channel quantization
int8_t QSymm8PerChannelParams::quantize(float value, float scale) const
{
const float transformed = value / scale;
return static_cast<int8_t>(round(std::max(-128.0f, std::min(127.0f, transformed))));
}
float QSymm8PerChannelParams::dequantize(const int8_t value, float scale) const
{
return scale * (static_cast<float>(value));
}
QSymm8PerChannelRescaleParams QSymm8PerChannelRescaleParams::make_rescale_params(
const QSymm8PerChannelParams& weight_quant,
const QSymm8PerChannelParams& input_quant,
const QSymm8PerChannelParams& output_quant
)
{
std::vector<int32_t> shifts;
std::vector<int32_t> mults;
std::vector<float> rescales;
for(size_t s = 0; s< input_quant.scales.size(); s++)
{
// Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
const float rescale = weight_quant.scales[s] * input_quant.scales[s] / output_quant.scales[s];
const float shiftf = round(log2(0.5f / rescale));
const float multf = exp2(31.0f + shiftf)*rescale;
int64_t shift = static_cast<int64_t>(shiftf);
int64_t mult = static_cast<int64_t>(multf);
if (mult == (1ll << 31))
{
mult /= 2;
shift--;
}
assert(shift >= 0);
assert(mult <= std::numeric_limits<int32_t>::max());
shifts.push_back(static_cast<int32_t>(shift));
mults.push_back(static_cast<int32_t>(mult));
rescales.push_back(rescale);
}
return QSymm8PerChannelRescaleParams(shifts, mults, rescales);
}
QSymm8PerChannelRescaleParams QSymm8PerChannelRescaleParams::make_rescale_params(
const QSymm8PerChannelParams& weight_quant,
const qasymm8::QAsymm8Params& input_quant,
const qasymm8::QAsymm8Params& output_quant
)
{
std::vector<int32_t> shifts;
std::vector<int32_t> mults;
std::vector<float> rescales;
for(size_t s = 0; s< weight_quant.scales.size(); s++)
{
// Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
const float rescale = weight_quant.scales[s] * input_quant.scale / output_quant.scale;
const float shiftf = round(log2(0.5f / rescale));
const float multf = exp2(31.0f + shiftf)*rescale;
int64_t shift = static_cast<int64_t>(shiftf);
int64_t mult = static_cast<int64_t>(multf);
if (mult == (1ll << 31))
{
mult /= 2;
shift--;
}
assert(shift >= 0);
assert(mult <= std::numeric_limits<int32_t>::max());
shifts.push_back(static_cast<int32_t>(shift));
mults.push_back(static_cast<int32_t>(mult));
rescales.push_back(rescale);
}
return QSymm8PerChannelRescaleParams(shifts, mults, rescales);
}
QSymm8PerChannelRescaleParams::QSymm8PerChannelRescaleParams(std::vector<int32_t>& shifts, std::vector<int32_t>& multipliers, std::vector<float>& rescales)
: shifts(shifts), multipliers(multipliers), rescales(rescales)
{
}
} // namespace qasymm8
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