What gets built

A cpmdc build produces one shared library, libcpmdc.so, and a few helpers around it. The build has two modes, selected by the Meson option with_cpmd:

Mode	Option	Evaluator behind the C ABI	cpmdc_available()
Default	-Dwith_cpmd=false	deterministic reference evaluator, no OpenCPMD	1
OpenCPMD	-Dwith_cpmd=true -Dcpmd_root=DIR	OpenCPMD linked from DIR/lib/libcpmd.a	1

Both modes export the same symbols. A third target, libcpmdc_stub.a, is a link-only placeholder: every call fails and cpmdc_available() returns 0. The tests use it to check the ABI without a working evaluator.

Artifact	Installed as	Purpose
libcpmdc.so	lib/libcpmdc.so.0	the C ABI from include/cpmdc.h
public headers	include/cpmdc/cpmdc.h, cpmdc_features.h, cpmdc_restart.h	declarations for hosts
libcpmdc_restart.a	lib/libcpmdc_restart.a	reader and writer for CPMD RESTART files
cpmdc-restart	bin/cpmdc-restart	command-line front end to libcpmdc_restart
pkg-config files	cpmdc.pc, cpmdc-restart.pc	compiler and linker flags
CMake package	cpmdcConfig.cmake	imported target cpmdc::cpmdc

Requirements

The checked-in Pixi manifest pins every build dependency. Without Pixi, install the same set from your package manager:

Dependency	Version in pixi.toml	Needed for
Meson, Ninja	Meson 1.5.2 or newer, Ninja 1.11 or newer	every build
Cap’n Proto (capnp compiler)	1.0.2 or newer, below 2	generating the schema readers, encoding messages
C and Fortran compilers	any recent GCC and gfortran	every build
pkg-config	2.5.1 or newer	dependency lookup
Python 3	3.10 or newer	build helpers and tests
cmocka	1.1.7 or newer	-Dwith_tests=true
MPI with Fortran bindings, BLAS and LAPACK	OpenMPI 4.1 to 5, OpenBLAS 0.3	-Dwith_cpmd=true
FFTW3	optional	linked when OpenCPMD was configured with FFTW3

Meson fetches three subprojects on the first meson setup: the C Cap’n Proto runtime (c-capnproto), the shared schema (potentials-schema, pinned in subprojects/potentials-schema.wrap), and capnp-fortran. On a machine without network access, download them first where the network is available:

meson subprojects download

Build the default library

Clone the repository and run the default suite:

git clone https://github.com/OmniPotentRPC/cpmdc.git
cd cpmdc
pixi run test-stub

test-stub configures build/ with tests on, compiles, and runs the Meson suite. A healthy run ends with every test reported OK and Fail: 0. The same steps without Pixi:

meson setup build -Dwith_tests=true
meson compile -C build
meson test -C build --print-errorlogs

Meson options

Option	Type	Default	Effect
with_tests	boolean	true	build the cmocka suites, contract checks, and example_host_step
with_cpmd	boolean	false	link OpenCPMD instead of the reference evaluator
cpmd_root	string	empty	OpenCPMD build tree holding lib/libcpmd.a, obj/, and src/

with_cpmd=true only takes effect together with a non-empty cpmd_root. Configuration stops when DIR/lib/libcpmd.a or DIR/obj/timetag.o is missing. OpenCPMD keeps timetag outside the archive, and header calls it.

Build against OpenCPMD

The OpenCPMD archive needs the patches in tools/ and position-independent code; the archive how-to covers that build. With the archive in place:

export CPMD_ROOT=/path/to/opencpmd-build
meson setup build-cpmd \
  -Dwith_cpmd=true \
  -Dcpmd_root="$CPMD_ROOT" \
  -Dwith_tests=true
meson compile -C build-cpmd
meson test -C build-cpmd --print-errorlogs

The link uses the MPI Fortran dependency, OpenBLAS (or LAPACK and BLAS when OpenBLAS is absent), FFTW3 when found, libgfortran, and libquadmath. When OpenCPMD was built with MPI compiler wrappers, configure with the same wrappers so both sides agree on one MPI:

CC=mpicc FC=mpif90 meson setup build-cpmd \
  -Dwith_cpmd=true -Dcpmd_root="$CPMD_ROOT"

Install

meson setup build-install --prefix "$HOME/.local" -Dwith_tests=false
meson install -C build-install
pkg-config --modversion cpmdc

The last command prints the project version from meson.build. Hosts that load the library at run time, such as rgpot, look for it through CPMDC_LIBRARY; see the environment reference.

Pixi tasks

Task	Environment	Runs
test-stub	default	configure build/, compile, full Meson suite
test-cmocka	default	the cmocka suite only
test-e2e	default	the e2e suite only (single point and optimizer session)
test-stub-sanitize	default	full suite in build-sanitize/ under AddressSanitizer and UndefinedBehaviorSanitizer
fortran-lint	default	fprettify --diff over src/*.f90
prek, prek-install, prek-validate	default	pre-commit hooks from prek.toml
lychee	default	link check over README, docs/orgmode, and news fragments
release-assert, towncrier-draft, release-cog-dry	default	release metadata checks
mkrst	docs	export docs/orgmode to docs/source RST
doxybuild	docs	Doxygen XML and Doxyrest pages for the public headers
sphinxbld, docbld	docs	mkrst, doxybuild, then the Sphinx HTML site in docs/build

Run a docs task with pixi run -e docs docbld. The published site is cpmdc.rgoswami.me.