fp256 is an efficient library implemented in C and assembly for 256 bit integer arithmetic.
It supports Windows, Linux and Macosx on x86_64 and arm64 processor, and can be compiled with MSVC, mingw-w64, gcc and clang.
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Use 4×64bit to represent 256 bit integer.
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Leveled api :
low level api operates directly on integer array, most low level api are specific for 256 bit integer, there are also a few api for arbitrary length array.
high level api operates on 256 bit integer. -
Most low level arithmetic are implemented in assembly, including
add,mul,u256 mul,div,shift,exgcd,mont mul, etc, they are very efficient and (maybe)well commented, see ll/x64, ll/aarch64 and ll/riscv64.
$ mkdir build
$ cd build
$ cmake ..
$ make -j
$ make test
Or cross compilation (cmake toolchain files are here):
$ mkdir build
$ cd build
$ cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchain/aarch64-linux-gcc.cmake ..
$ make -j
-DCMAKE_BUILD_TYPE : possible values are empty, Debug, Release, RelWithDebInfo and MinSizeRel, default is Release.
-DCMAKE_INSTALL_PREFIX : where to install fp256 library, default is /usr/local.
-DBUILD_STATIC : build static library, default is ON.
-DBUILD_SHARED : build shared library, default is ON.
-DUSE_DEV_RANDOM : use /dev/random to get random number, default is OFF(use /dev/urandom).
-DUSE_ASM : use assembly code, default is ON. it can not be turned off since some algorithms have no C implementation to fall back yet.
-DUSE_ASAN : use AddressSanitizer, default is OFF.
- Add prime test, modular exponential, square root related, etc.
- Constant-time implementation of division and exgcd.
- more tests.
Some of benchmark results are listed below. Build and run build/bench/bench to get full result.
| arithmetic(256 bit) | cycles / op | op / s |
|---|---|---|
| naive div | 428 | 4890000 |
| gcd | 3784 | 554000 |
| mod add | 330 | 6340000 |
| mod sqr | 491 | 4260000 |
| mod mul | 509 | 4110000 |
| mod inv | 4628 | 453000 |
| mod exp | 17000 | 123000 |
| mont mul | 130 | 16000000 |
| mont sqr | 117 | 17800000 |
Apache 2.0