Report on energy-efficiency evaluation of several NWP model configurations

TL;DR

This report evaluates the energy efficiency of various numerical weather prediction models and configurations on different hardware, revealing a U-shaped energy consumption pattern and comparing CPU and optical processors.

Contribution

It provides the first detailed energy consumption measurements of NWP models on Intel CPUs and optical processors, exploring performance-energy trade-offs and hardware comparisons.

Findings

Energy consumption shows a U-shaped dependence on performance.

Optalysys optical processors are more energy-efficient but less precise and slower.

CPU models outperform optical processors in speed and accuracy.

Abstract

This document is one of the deliverable reports created for the ESCAPE project. ESCAPE stands for Energy-efficient Scalable Algorithms for Weather Prediction at Exascale. The project develops world-class, extreme-scale computing capabilities for European operational numerical weather prediction and future climate models. This is done by identifying Weather & Climate dwarfs which are key patterns in terms of computation and communication (in the spirit of the Berkeley dwarfs). These dwarfs are then optimised for different hardware architectures (single and multi-node) and alternative algorithms are explored. Performance portability is addressed through the use of domain specific languages. In this deliverable we report on energy consumption measurements of a number of NWP models/dwarfs on the Intel E5-2697v4 processor. The chosen energy metrics and energy measurement methods are documented. Energy measurements are performed on the Bi-Fourier dwarf (BiFFT), the Acraneb dwarf, the ALARO 2.5 km Local Area Model reference configuration (B\'enard et al. 2010, Bubnova et al. 1995) and on the COSMO-EULAG Local Area Model reference configuration (Piotrowski et al. 2018). The results show a U-shaped dependence of the consumed energy on the wall-clock time performance. This shape can be explained from the dependence of the average power of the compute nodes on the total number of cores used. We compare the energy consumption of the BiFFT dwarf on the E5-2697v4 processor to that on the Optalysys optical processors. The latter are found to be much less energy costly, but at the same time it is also the only metric where they outperform the classical CPU. They are non-competitive as far as wall-clock time and especially numerical precision are concerned.