114 lines
3.0 KiB
C++
114 lines
3.0 KiB
C++
#pragma once
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/*
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* Copyright (c) 2018 Stanislav Denisov
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include <cstdint>
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#include <cstring>
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namespace bitstream
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{
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/**
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* @brief Class for quantizing single-precision floats into half-precision
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*/
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class half_precision
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{
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public:
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inline static uint16_t quantize(float value) noexcept
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{
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int32_t tmp;
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std::memcpy(&tmp, &value, sizeof(float));
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int32_t s = (tmp >> 16) & 0x00008000;
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int32_t e = ((tmp >> 23) & 0X000000FF) - (127 - 15);
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int32_t m = tmp & 0X007FFFFF;
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if (e <= 0) {
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if (e < -10)
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return static_cast<uint16_t>(s);
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m |= 0x00800000;
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int32_t t = 14 - e;
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int32_t a = (1 << (t - 1)) - 1;
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int32_t b = (m >> t) & 1;
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m = (m + a + b) >> t;
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return static_cast<uint16_t>(s | m);
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}
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if (e == 0XFF - (127 - 15)) {
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if (m == 0)
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return static_cast<uint16_t>(s | 0X7C00);
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m >>= 13;
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return static_cast<uint16_t>(s | 0X7C00 | m | ((m == 0) ? 1 : 0));
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}
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m = m + 0X00000FFF + ((m >> 13) & 1);
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if ((m & 0x00800000) != 0) {
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m = 0;
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e++;
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}
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if (e > 30)
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return static_cast<uint16_t>(s | 0X7C00);
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return static_cast<uint16_t>(s | (e << 10) | (m >> 13));
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}
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inline static float dequantize(uint16_t value) noexcept
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{
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uint32_t tmp;
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uint32_t mantissa = static_cast<uint32_t>(value & 1023);
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uint32_t exponent = 0XFFFFFFF2;
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if ((value & -33792) == 0) {
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if (mantissa != 0) {
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while ((mantissa & 1024) == 0) {
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exponent--;
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mantissa <<= 1;
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}
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mantissa &= 0XFFFFFBFF;
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tmp = ((static_cast<uint32_t>(value) & 0x8000) << 16) | ((exponent + 127) << 23) | (mantissa << 13);
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}
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else
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{
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tmp = static_cast<uint32_t>((value & 0x8000) << 16);
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}
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}
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else
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{
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tmp = ((static_cast<uint32_t>(value) & 0x8000) << 16) | (((((static_cast<uint32_t>(value) >> 10) & 0X1F) - 15) + 127) << 23) | (mantissa << 13);
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}
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float result;
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std::memcpy(&result, &tmp, sizeof(float));
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return result;
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}
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};
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} |