| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * 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 |
| * |
| * http://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. |
| */ |
| |
| #ifndef LIBTEXTCLASSIFIER_COMMON_FLOAT16_H_ |
| #define LIBTEXTCLASSIFIER_COMMON_FLOAT16_H_ |
| |
| #include "util/base/casts.h" |
| #include "util/base/integral_types.h" |
| |
| namespace libtextclassifier { |
| namespace nlp_core { |
| |
| // 16 bit encoding of a float. NOTE: can't be used directly for computation: |
| // one first needs to convert it to a normal float, using Float16To32. |
| // |
| // Documentation copied from original file: |
| // |
| // Compact 16-bit encoding of floating point numbers. This |
| // representation uses 1 bit for the sign, 8 bits for the exponent and |
| // 7 bits for the mantissa. It is assumed that floats are in IEEE 754 |
| // format so a float16 is just bits 16-31 of a single precision float. |
| // |
| // NOTE: The IEEE floating point standard defines a float16 format that |
| // is different than this format (it has fewer bits of exponent and more |
| // bits of mantissa). We don't use that format here because conversion |
| // to/from 32-bit floats is more complex for that format, and the |
| // conversion for this format is very simple. |
| // |
| // <---------float16------------> |
| // s e e e e e e e e f f f f f f f f f f f f f f f f f f f f f f f |
| // <------------------------------float--------------------------> |
| // 3 3 2 2 1 1 0 |
| // 1 0 3 2 5 4 0 |
| |
| typedef uint16 float16; |
| |
| static inline float16 Float32To16(float f) { |
| // Note that we just truncate the mantissa bits: we make no effort to |
| // do any smarter rounding. |
| return (bit_cast<uint32>(f) >> 16) & 0xffff; |
| } |
| |
| static inline float Float16To32(float16 f) { |
| // We fill in the new mantissa bits with 0, and don't do anything smarter. |
| return bit_cast<float>(f << 16); |
| } |
| |
| } // namespace nlp_core |
| } // namespace libtextclassifier |
| |
| #endif // LIBTEXTCLASSIFIER_COMMON_FLOAT16_H_ |