This repository provides a few examples of the division by multiplication method using NASM. It also includes a program to calculate the parameters required by the division by multiplication method. For the division by multiplication method itself, please see my note posted at Factor Network.

The following three directories contain source files.

• find_magic_number: The source files for the program to calculate the parameters. You can build and install this program, if you like. The build of this program requires GNU Multiple Precision Arithmetic Library (GMP). If it is not installed on your computer, the build process automatically downloads its source code and builds the GMP library.

• nasm_examples: Examples of the division by multiplication method implemented in NASM. You can build a library including the example functions. But it is not built by default, because the library is only used for the unit tests of the example codes.

• tests: The unit test files for the codes in nasm_examples. If you build them, the test executables are build/tests/test_{signed,unsigned}_div_by_[neg_]<divisor>_{zero,up,down}_{32,64}. You can run all of the tests at once by the ctest command. The build of the tests requires the Unity unit testing framework. If it is not installed on your computer, the build process automatically downloads it and builds the required library.

To build the find_margic_number program and install it to the standard binary directory, run the following commands in the project root directory.

mkdir build
cmake -S . -B build 
cmake --build build
cmake --install 

If you also want to build the nasm example library and unit tests, run the following commands intead:

mkdir build
cmake -Dtest_nasm_examples=True -S . -B build 
cmake --build build
cmake --install 

The test executable is build/tests/division_tests.