Getting started with Conquest for ISC24 SCC

Owned by Ophir Maor
Last updated: Apr 04, 2024
3 min read

 

Overview

CONQUEST is a DFT code designed for large-scale calculations, with excellent parallelisation. It gives an exact diagonalisation approach for systems from 1 to 10,000+ atoms, and brings the possibility of linear scaling calculations on over 1,000,000 atoms. In this task, you will be using the linear scaling approach, which can show perfect weak scaling of thousands of cores.

 

Note: The page may be changed until the competition stats, maybe sure to follow up until the opening ceremony.

 

Conquest presentation to the teams:

 

Presentation file:

Building and Running example

Download v1.2 from GitHub - OrderN/CONQUEST-release: Full public release of large scale and linear scaling DFT code CONQUEST.

wget https://github.com/OrderN/CONQUEST-release/releases/download/v1.2/CONQUEST-release-1.2.tar.gz

Download libxc 6.2.2 from https://www.tddft.org/programs/libxc/download/.

 

Prerequisites

  • FFTW/MKL package

  • SCALAPACK

 

Build libxc:

# Load intel compilers and mpi modules cd libxc-6.2.2 ./configure --prefix=<path> CC=mpicc FC=mpif90 make make install

 

Build Conquest:

# Load intel compilers and mpi modules cd CONQUEST-release/src # Edit system.make for XC lib and include paths, and FFT & blas libraries. # Add correct flag (-qopenmp for Intel) for OpenMP to compile and link arguments # Set MULT_KERN to ompGemm make

 

Sample build script for libxc and Conquest on PSC:

Modify src/system.make under Conquest source directory,

Build Conquest:

Running Conquest:

 

You will need to set the number of threads per process for OpenMP as well as the number of MPI processes.

 

Application metric is wall-time “Total run time”.

Tasks & Submissions

Input:

The virtual task involves performing linear scaling calculations on samples of bulk silicon with different numbers of atoms. Conquest weak scaling is seen when the number of atoms per MPI process is kept fixed, and the number of processes is scaled with the system size (number of atoms). You have been provided with three inputs, with 512 atoms (si_444.xtl), 1728 atoms (si_666.xtl) and 4096 atoms (si_888.xtl). The minimum number of atoms per MPI process is 8; the maximum will be dictated by memory limitations. The simplest way to examine weak scaling is to keep the product of MPI processes and OpenMP threads per process constant, and vary system size. You might also explore the effect of under-populating nodes where that is possible.

The smaller inputs are only for practice, not for submissions. The only input for submission is si_888.xtl.

  1. Find the best balance between OpenMP threads and MPI processes, show your work in the team’s interview presentation. Investigate the weak scaling (with the other inputs) as the MPI/OpenMP balance is changed. present your work in the interview.

  2. Run CONQUEST on 4 nodes and submit the results to the team’s folder (any number of PPN you choose).

  3. Run IPM profile or any other MPI profile on 4 nodes, and find the 3 most used MPI calls, show your work in the team interview presentation.

  4. Try run the application on 1,2,4 nodes (for the si_888.xtl input) and present strong scaling graph in the teams interview presentation.