一个 C/C++ 头文件,用于在 64 位硬件上进行快速的 32 位整除余数 (以及整除性测试)。
A header-only library for fast 32-bit division and remainder operations on 64-bit hardware.
This library provides optimized implementations that can outperform compiler-generated code for constant divisors, making it ideal for performance-critical applications like hashing algorithms.
Clone the repository and include include/fastmod.h in your project.
git clone https://github.com/lemire/fastmod.gitSince it's header-only, no additional installation steps are required.
Include the header in your C or C++ file:
#include "fastmod.h"For C++, use the fastmod namespace:
#include "fastmod.h"
// Use fastmod::function_nameuint64_t computeM_u32(uint32_t d): Compute the multiplier for divisor d (do once per divisor).uint32_t fastmod_u32(uint64_t a, uint64_t M, uint32_t d): Compute a % d.uint32_t fastdiv_u32(uint64_t a, uint64_t M): Compute a / d (requires d > 1).bool is_divisible(uint64_t a, uint64_t M): Check if a is divisible by d.uint64_t computeM_s32(int32_t d): Compute the multiplier for divisor d (use absolute value for d).int32_t fastmod_s32(int64_t a, uint64_t M, int32_t positive_d): Compute a % d.int32_t fastdiv_s32(int64_t a, uint64_t M, int32_t d): Compute a / d (avoid d in {-1, 1, INT32_MIN}).#include "fastmod.h"
// Unsigned example
uint32_t d = 7;
uint64_t M = computeM_u32(d);
uint32_t result = fastmod_u32(100, M, d); // 100 % 7
// Signed example
int32_t sd = -5;
int32_t pos_d = sd < 0 ? -sd : sd;
uint64_t SM = computeM_s32(sd);
int32_t sresult = fastmod_s32(-100, SM, pos_d); // -100 % -5make
./unitcmake -B build
cmake --build build
ctest --test-dir build --output-on-failureFor exhaustive tests:
cmake -B build -DFASTMOD_EXHAUSTIVE_TESTS=ON
cmake --build build
ctest --test-dir build --output-on-failureEnsure you're building for 64-bit (x64 or ARM64).
cmake -B build
cmake --build build --config Release
ctest --test-dir build --output-on-failure -C ReleaseIn hashing benchmarks on Intel Skylake with Clang, this library outperforms compiler optimizations.
For 64-bit operations (experimental):
make benchmarkRequires C++11, not supported on Visual Studio.
Contributions are welcome! Please:
This project is licensed under the Apache License 2.0 - see the LICENSE file for details.
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