Efficient Fock matrix construction in localized Hartree-Fock method

Project reference: 2108

Solution of independent-particle model (DFT or Hartree-Fock method) is one of the key targets of many quantum chemistry codes. Hartree-Fock method is iterative procedure which consist of two time-consuming steps. First, construction of Fock matrix from integrals and density matrix. Second, diagonalization of constructed Fock matrix.

Several years ago we effectively removed diagonalization step which was replaced by matrix-matrix multiplications. Very recently we implemented the solution of Hartree-Fock equations in localised orbitals, which opens the route toward a code applicable for very large molecules. To initialize the process, integrals are transformed to localized molecular orbital basis and are used during the entire run. Integrals matrix should be sparse by construction. Density matrix is updated in each step of the iterative procedure and for big systems it is sparse, as well. Currently, Fock matrix construction is implemented only in a sequential mode.

Students are expected to cooperate on implementation and performance testing of Fock matrix construction. Two different approaches will be implemented and tested.

First, BLAS version combined with OpenMP or MPI. Second we would like to implement Fock matrix construction using sparse matrix multiplications. Both algorithms will be implemented in local version of quantum chemistry program DIRCCR12OS which is mostly coded in fortran. It contains working MPI environment so students will be using several routines already implemented in the code.

Traditional Hartree-Fock method scheme for large-scale molecules calculations (in this case with phenylalanine peptide fragment as a test case).

Project Mentor: RNDr. Ján Simunek, PhD.

Project Co-mentor: Prof. Dr. Jozef Noga

Site Co-ordinator: Mgr. Lukáš Demovič, PhD.

Participants: Ioannis Savvidis, Eduárd Zsurka

Learning Outcomes:
Student will learn about Fortran and MPI environments. He/she will also get familiar with ideas of efficient use of tensor-contractions and parallel I/O in quantum chemistry algorithms.

Student Prerequisites (compulsory):
Background in quantum-chemistry or physics.

Student Prerequisites (desirable):
Advanced knowledge of Fortran, basic knowledge of MPI, BLAS libraries and other HPC tools.

Training Materials:
https://training.prace-ri.eu/index.php/prace-tutorials/

Workplan:

• Week 1: training with existing code;
• Weeks 2-3: introduction to fortran, MPI and theory of implemented Hartree-Fock method,
• Weeks 4-7: implementation, optimization and extensive testing/benchmarking of the code,
• Week 8: report completion and presentation preparation

Final Product Description:
We believe that the resulting code will be capable of successfully completing local Hartree-Fock calculations using at least several computational nodes. Codes will be benchmarked and compared with the previously used versions of HF calculations.

Adapting the Project: Increasing the Difficulty:
The goal is to push the efficiency of the MPI code(s) to maximum.

Adapting the Project: Decreasing the Difficulty:
Any successful implementation of local Hartree-Fock using MPI or with sparse matrix multiplications will be something new and acceptable from our side.

Resources:
Student will have access to the necessary learning material, as well as to our local IBM P775 supercomputer and x86 infiniband clusters.

Organisation:

CC SAS-Computing Centre, Centre of Operations of the Slovak Academy of Sciences