Modular Boost

Technically, Modular Boost consists of the Boost super-project and separate projects for each individual library in Boost. In terms of Git, the Boost super-project treats the individual libraries as submodules. Currently (early 2024) when the Boost libraries are downloaded and installed, the build organization does not match the modular arrangement of the Git super-project. This is largely a legacy issue, and there are advantages to the build layout matching the super-project layout. This concept, and the effort behind it, is now known as "Modular Boost".

In the past, the term has been used more broadly to refer simply to libraries in different repositories. This definition has now been tightened to mean a flat layout where each library is in its own sub-module, and there are no sub-libraries as there have been in the past (for example, the numeric libraries).

Refer to Super-Project Layout for a full description of the super-project.

It’s when the libraries can be used, and hence built, without creating the monolithic headers, without needing the root build files, and without needing the libraries to be arranged in the usual root/libs/<name> format.

No, unless you want to. You will still be able to test with the current non-modular way. But you could also test the modular way.

The structure is still required for things like testing and documentation building.

The numeric libraries have been divided into four packages: libboost-numeric-conversion/, libboost-numeric-interval/, libboost-numeric-odeint/, libboost-numeric-ublas/.