Compositional Numeric Library

The Compositional Numeric Library (CNL) is a C++ library of fixed-precision numeric classes which enhance integers to deliver safer, simpler, cheaper arithmetic types. Documentation can be found here. You can try out CNL on Compiler Explorer here.

CNL is particularly well-suited to:

• compute or energy-constrained environments where FPUs are absent or costly;
• compute or energy-intensive environments where arithmetic is the bottleneck such as simulations, machine learning applications and DSPs; and
• domains such as finance where precision is essential.

Requirements

The latest version of CNL requires a C++20-compatible tool chain. (Version 1.x supports C++11.) CNL is continually tested on the following systems:

Linux

Tested:

• GCC 10, 11, 12
• Clang 10, 11, 12, 13, 14
• libstdc++ 10, 11, 12
• libc++ 13, 14
• CMake 3.23.1
• Conan 1.48.1

OS X

Tested:

• GCC 11 / Clang 13
• CMake 3.23.1
• Conan 1.48.1

Windows

Tested:

• Visual Studio 2019 Version 16 (19.29.30145.0)
• Visual Studio 2022 Version 17 (19.32.31329.0)
• CMake 3.23.1
• Conan 1.48.1

Instructions

Build

CMake scripts are provided.

• To build and install CNL on your system:

mkdir build && cd build
cmake ..
cmake --build . --target install

Note: you may need user privileges to install the library. Alternatively, you can install to user directory using CMAKE_INSTALL_PREFIX:

mkdir build && cd build
cmake -DCMAKE_INSTALL_PREFIX:FILE=/home/username/someplace ..
cmake --build . --target install

Alternatively, CNL is a header-only library so you can simply point to the include directory

c++ -isystem /path/to/cnl/include -std=c++20 my_program.cpp

or even include the root header directly in your code:

#include "/path/to/cnl/include/cnl/all.h"

Test

The test suite uses CMake and depends on Google Test and Google Benchmark. Optional integration tests use Boost.Multiprecision.

1. Conan can be used to pull in essential dependencies. This example assumes GCC but other tool chain files are provided:

   cd build
   conan profile new --detect --force default
   conan profile update settings.compiler.libcxx=libstdc++11 default  # GCC/Clang only
   conan profile update env.CONAN_CMAKE_TOOLCHAIN_FILE=../test/toolchain/gcc.cmake default # GCC only
   conan install --build=missing --options test=unit ..

   ... and then configure, build and run unit tests:

   conan build --configure --build --test ..

2. To run benchmarks, use --options test=benchmark...

   conan install --build=missing --options test=benchmark ..

   then configure and build

   conan build --configure --build ..

   and finally run explicitly to see the results.

   ./test/benchmark/test-benchmark

Integration

The API is exposed through headers in the include directory. Add this to your system header list and include, e.g.:

// to use a specific type:
#include <cnl/scaled_integer.h>

// or to include all CNL types:
#include <cnl/all.h>

Example Projects

Examples of projects using CNL:

• CDSP - Compositional DSP Library for C++;
• BrewBlox firmware - firmware for a brewery controller
• cnl_example - minimal CMake-based project which uses CNL as a dependency.

Further Reading

• CNL documentation
• CppCon 2017 presentation
• Embedded Artistry article
• ISO C++ papers:
  • P0037 - Fixed-Point Real Numbers
  • P0554 - Composition of Arithmetic Types
  • P0827 - General-Purpose Constant Value Type
  • P0828 - Elastic Integers
  • P1050 - Fractional Numeric Type

Alternatives

• Much of the simplicity and efficiency in CNL's API design can be traced back to Matheus Izvekov's fp fixed point library.
• Together with Lawrence Crowl's fixed-point paper, P0106, it lays the groundwork for integer-backed real number approximation that minimizes loss of performance and precision.
• fpm is a fixed-point math library with a high quantity of mathematical functions.
• Fixed Point Class is a single-header C++98 solution from Peter Schregle's.

Contact Information

All feedback greatly appreciated.

• CNL Issues
• cnl@john.mcfarlane.name