libgecode-dev binary package in Ubuntu Focal amd64

 Gecode is a toolkit for developing constraint-based systems and
 applications. Gecode provides a constraint solver with
 state-of-the-art performance while being modular and extensible.
 .
 Gecode is radically open for programming: it can be easily
 interfaced to other systems. It supports the programming of new
 propagators (as implementation of constraints), branching strategies,
 and search engines. New variable domains can be programmed at the same
 level of efficiency as finite domain and integer set variables that
 come predefined with Gecode.

Source package