1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef NLP_SAFT_COMPONENTS_COMMON_MOBILE_LITE_BASE_FLOAT16_H_ 18 #define NLP_SAFT_COMPONENTS_COMMON_MOBILE_LITE_BASE_FLOAT16_H_ 19 20 #include "lang_id/common/lite_base/casts.h" 21 #include "lang_id/common/lite_base/integral-types.h" 22 23 namespace libtextclassifier3 { 24 namespace mobile { 25 26 // 16 bit encoding of a float. NOTE: can't be used directly for computation: 27 // one first needs to convert it to a normal float, using Float16To32. 28 // 29 // Compact 16-bit encoding of floating point numbers. This 30 // representation uses 1 bit for the sign, 8 bits for the exponent and 31 // 7 bits for the mantissa. It is assumed that floats are in IEEE 754 32 // format so a float16 is just bits 16-31 of a single precision float. 33 // 34 // NOTE: The IEEE floating point standard defines a float16 format that 35 // is different than this format (it has fewer bits of exponent and more 36 // bits of mantissa). We don't use that format here because conversion 37 // to/from 32-bit floats is more complex for that format, and the 38 // conversion for this format is very simple. 39 // 40 // <---------float16------------> 41 // 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 42 // <------------------------------float--------------------------> 43 // 3 3 2 2 1 1 0 44 // 1 0 3 2 5 4 0 45 46 typedef uint16 float16; 47 48 static inline float16 Float32To16(float f) { 49 // Note that we just truncate the mantissa bits: we make no effort to 50 // do any smarter rounding. 51 return (bit_cast<uint32>(f) >> 16) & 0xffff; 52 } 53 54 static inline float Float16To32(float16 f) { 55 // We fill in the new mantissa bits with 0, and don't do anything smarter. 56 return bit_cast<float>(f << 16); 57 } 58 59 } // namespace mobile 60 } // namespace nlp_saft 61 62 #endif // NLP_SAFT_COMPONENTS_COMMON_MOBILE_LITE_BASE_FLOAT16_H_ 63
