Making PyQuante work with Libint

Pyquante is a very nice “open-source suite of programs for developing quantum chemistry methods” developed by Richard Muller. Although not as fast as comercial software, I can atest that the code is very simple to understand and to modify. And in case you need to implement your own Quantum Chemistry routines, PyQuante takes you off the burden of having to write everything from scratch.

Libint is a software stack for computing integrals found in Quantum Chemistry created by Edward Valeev. I certainly cannot say much about libint as I haven’t had enough time to fiddle around with it. What I can say is that Gabriele Lanaro wrote some bindings that allow PyQuante to use libint and that make the calculation of the integrals faster (I cannot give you exact figures, since I never did any rigorous runtime tests, but I can attest that for the situations I tested, it did indeed run faster – also the ground state energy was indeed the same).

My problem was that I did not find any instructions on how to make PyQuante work with libint.
So here are my own (they works for PyQuante 1.6.4 and libint-1.1.4)

Download libint 1.1.4 and then compile it by doing:

./configure --enable-shared

If using Ubuntu (and possibly other Linux distros) you may get an error similar to:

/bin/sh ./libtool --mode=compile g++ -DHAVE_CONFIG_H -D_ISOC99_SOURCE=1 
-I./include -I/data/development/libint-2.0.3-stable/./include -O2 -c src/ -o src/HRRPart1bra0ket0gf.lo
./libtool: 1: eval: base_compile+= g++: not found
./libtool: 1: eval: base_compile+= -DHAVE_CONFIG_H: not found
./libtool: 1: eval: base_compile+= -D_ISOC99_SOURCE=1: not found
./libtool: 1: eval: base_compile+= -I./include: not found
./libtool: 1: eval: base_compile+= -I/data/development/libint-2.0.3-stable/./include: not found
./libtool: 1: eval: base_compile+= -O2: not found
./libtool: 1: eval: base_compile+= -c: not found
./libtool: 1: eval: CC_quoted+= gcc: not found
./libtool: 1: eval: CC_quoted+= g++: not found
libtool: compile: you must specify a compilation command
libtool: compile: Try `libtool --help --mode=compile' for more information.
make: *** [src/HRRPart1bra0ket0gf.lo] Error 1

This is due to the fact that in Ubuntu 6.10, the default system shell, /bin/sh, was changed to dash.
Changing the shell to bash by adding

SHELL = /bin/bash

to the Makefile should solve the problem.
Now download PyQuante 1.6.4 and copy the folder libint-1.1-4 to PyQuante’s folder and install PyQuante with libint support by running

sudo python install --enable-libint


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Everything should be working now, and the integrations should now be now faster than before!