This repository contains version 2 of QMC=Chem. Version 1 is available on GitLab. QMC=Chem is a quantum Monte Carlo program meant to be used after preparing a trial wave function with the Quantum Package code.

The documentation is available on ReadTheDocs.

Requirements

• Bash
• Python3
• Fortran compiler, Intel Fortran recommended
• Lapack library, Intel MKL recommended
• ZeroMQ high performance communication library
• F77_ZMQ ZeroMQ Fortran interface: https://github.com/zeromq/f77_zmq/releases/download/v4.3.3/f77-zmq-4.3.3.tar.gz
• QMCkl library: https://github.com/TREX-CoE/qmckl/releases/download/v0.3.1/qmckl-0.3.1.tar.gz
• TREXIO library: https://github.com/TREX-CoE/trexio/releases/download/v2.2.0/trexio-2.2.0.tar.gz
• OCaml compiler with Opam

To install the required OCaml packages, run

opam install ocamlbuild cryptokit zmq sexplib ppx_sexp_conv ppx_deriving getopt trexio

If you have trouble installing OCaml, on x86 systems you can download the this file and run

tar -zxf ocaml-bundle_x86.tar.gz
./ocaml-bundle/bootstrap.sh
./ocaml-bundle/configure.sh
./ocaml-bundle/compile.sh 

Installation

To compile the program, run

$ ./autogen.sh
$ ./configure && make

Before using QMC=Chem, environment variables need to be loaded. The environment variables are located in the qmcchemrc file:

$ source qmcchemrc

The QMCCHEM_NIC environment variable should be set to the proper network interface, usually ib0 on HPC machines.

Tuning for the HPC system

The Intel compiler is preferred for better performance. With gfortan >= 12, the option -fallow-argument-mismatch should be added.

Here are a few examples:

# Ifort
./configure FC=ifort FCFLAGS="-O2 -g -ip -ftz -finline -xCORE-AVX2 -mkl=sequential"

# GCC >= 12
./configure FCFLAGS="-fallow-argument-mismatch -g -O2  -ffast-math  -march=native   -fno-trapping-math -fno-math-errno -ftree-vectorize -fno-stack-protector -fopenmp"

File preparation

To create files suitable for QMC=Chem, the save_for_qmcchem plugin needs to be installed in Quandtum Package. This can be done as

qp plugins download https://gitlab.com/scemama/qp_plugins_scemama
qp plugins install qmcchem
cd $QP_ROOT/src/qmcchem
ninja

Then, after running a Quantum Package calculation you should run

qp run save_for_qmcchem

to prepare the directory for use in QMC=Chem.

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TREX: Targeting Real Chemical Accuracy at the Exascale project has received funding from the European Union’s Horizon 2020 - Research and Innovation program - under grant agreement no. 952165. The content of this document does not represent the opinion of the European Union, and the European Union is not responsible for any use that might be made of such content.