Code Authors: EvangelistaLab

Manual (http://forte.readthedocs.io/)

Web: evangelistalab.org

Forte is an open-source plugin to Psi4 (https://github.com/psi4/psi4) that implements a variety of quantum chemistry methods for strongly correlated electrons.

Download and compilation of Forte

Prior to the compilation of Forte you must first check to make sure you have the following:

1. CMake version 3.0 or higher

2. An updated version of Psi4 (obtain it from https://github.com/psi4/psi4)

3. The tensor library Ambit (obtain it from https://github.com/jturney/ambit). Note that ambit is included in the conda distribution of psi4. So if you already have the latest version of psi4 installed there is no need to compile ambit.

4. Pybind11

Once you have the current versions of Psi4, CMake, and Ambit, follow the following instructions to install Forte.

Download Forte

1. Open a terminal and change the current working directory to the location where you want to clone the Forte directory. Let's assume this is the folder src.

2. Clone Forte from GitHub by pasting the following command:

git clone git@github.com:evangelistalab/forte.git

The repository will be cloned in the folder src/forte

1. Compilation via setup.py (recommended)

The most convenient way to compile forte is using the setup.py script. To compile Forte do the following:

1. From the src directory change to the forte directory src/forte
2. Tell setup.py where to find ambit, which can be done by creating the src/forte/setup.cfg file and adding the following lines

[CMakeBuild]
ambitpath=<ambit install dir>

or alternatively by setting the environmental variable AMBITDIR to point to the ambit install directory (note: there is no need to append share/cmake/ambit)

export AMBITPATH=<ambit install dir>

3. Compile forte by calling

python setup.py develop 

or for Debug mode

python setup.py build_ext --debug develop

If using src/forte/setup.cfg, instead append the line debug=True to src/forte/setup.cfg and then use python setup.py develop as normal. This procedure will register forte within pip and you should be able to see forte listed just by calling

pip list

You can test that the path to Forte is set correctly by running python and importing forte:

import forte

2. Compilation via CMake

Forte may also be compiled by directly invoking CMake by following these instructions:

1. Run psi4 in the Forte folder

psi4 --plugin-compile

Psi4 will generate a CMake command for building Forte that looks like:

cmake -C /usr/local/psi4/stage/usr/local/psi4/share/cmake/psi4/psi4PluginCache.cmake
      -DCMAKE_PREFIX_PATH=/usr/local/psi4/stage/usr/local/psi4 .

2. Run the cmake command generated in 1. appending the location of Ambit's cmake files (via the -Dambit_DIR option):

 cmake -C /usr/local/psi4/stage/usr/local/psi4/share/cmake/psi4/psi4PluginCache.cmake
       -DCMAKE_PREFIX_PATH=/usr/local/psi4/stage/usr/local/psi4 .
       -Dambit_DIR=<ambit-bin-dir>/share/cmake/ambit

3. Run make

 make

Setting up the PYTHONPATH

If Forte is compiled with CMake, you will need to specify PYTHONPATH environment variable to make sure that it can be imported in python. Assuming that you cloned Forte from the folder src then you will have a folder named src/forte. Your PYTHONPATH should then include src/forte

# in bash
export PYTHONPATH=<homedir>/src/forte:$PYTHONPATH 

This allows Forte to be imported correctly since the main __init__.py file for Forte is found at src/forte/forte/__init__.py

CMake script

The following script automates the Forte compilation process

#! /bin/tcsh

# Modify the following four parameters
set ambit_dir = /Users/fevange/Bin/ambit-Release/share/cmake/ambit/ # <- location of ambit
set srcdir = /Users/fevange/Source/forte   # <- location of forte source
set build_type = Release # <- Release, Release, or RelWithDebInfo

# Run cmake
cd $srcdir

set cmake_psi4 = `psi4 --plugin-compile`

$cmake_psi4 \
-Dambit_DIR=$ambit_dir \ # remove this line if ambit is installed via conda
-DCMAKE_BUILD_TYPE=$build_type \
-DMAX_DET_ORB=128 \
-DPYTHON_EXECUTABLE=/opt/anaconda3/bin/python \
-DENABLE_ForteTests=TRUE \

make -j`getconf _NPROCESSORS_ONLN`

Advanced compilation options

Number of threads used to compile Forte

To speed up compilation of Forte specify the number of threads to use for compilation. This can be done in the setup.cfg file via

[CMakeBuild]
nprocs=<number of threads>

or when using CMake, compile Forte with the option -jn, for example, to compile with four threads

make -j4

Add configuration and build options

When using setup.py you can specify the CMAKE_CONFIG_OPTIONS and CMAKE_BUILD_OPTIONS passed internally to CMake in setup.cfg

[CMakeBuild]
cmake_config_options=...
cmake_build_options=...

These are convenient if you want to specify a different compiler from the one automatically detected by CMake.

Maximum number of orbitals in the Determinant class

By default, Forte is compiled assuming that the maximum number of orbitals that can be handled by codes that use the Determinant class is 64. To change this value modify the setup.cfg file to include

[CMakeBuild]
max_det_orb=<a multiple of 64>

or add the option

-DMAX_DET_ORB=<a multiple of 64>

if compiling with CMake.

Enabling code coverage

To enable compilation with code coverage activated, set the option enable_codecov to ON in the setup.cfg file

[CMakeBuild]
enable_codecov=ON

or add the option

-DENABLE_CODECOV=ON

if compiling with CMake.