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FFCx: The FEniCSx Form Compiler

FFCx CI Spack install Coverage Status

FFCx is a new version of the FEniCS Form Compiler. It is being actively developed and is compatible with DOLFINx.

FFCx is a compiler for finite element variational forms. From a high-level description of the form in the Unified Form Language (UFL), it generates efficient low-level C code that can be used to assemble the corresponding discrete operator (tensor). In particular, a bilinear form may be assembled into a matrix and a linear form may be assembled into a vector. FFCx may be used either from the command line (by invoking the ffcx command) or as a Python module (import ffcx).

FFCx is part of the FEniCS Project. For more information, visit


To install FFCx from PyPI:

$ pip install fenics-ffcx

To install FFCx from the source directory:

$ pip install .


Documentation can be viewed at

Interface file installation only

FFCx provides the ufcx.h interface header for finite element kernels, used by DOLFINx. ufcx.h is installed by FFCx within the Python site packages, but it is sometimes helpful to install only the header file. This can be done using cmake:

$ cmake -B build-dir -S cmake/
$ cmake --build build-dir
$ cmake --install build-dir


This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see