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DOI 10.5286/dltr.2012001
Persistent URL http://purl.org/net/epubs/work/62085
Record Status Checked
Record Id 62085
Title Final report for the gNEMO project: porting the oceanographic model NEMO to run on many-core devices
Abstract This report describes work done in the gNEMO project investigating whether general-purpose graphics processing units (GPUs) can be used to improve the performance of an ocean-modelling code, NEMO. The porting is performed using accelerator directives with the aim of minimising changes to the original Fortran source code. Although speed-up factors of between two and five were obtained for five out of the six subroutines tackled, this is only in comparison to a single CPU core. Once the routines were modified so as to make use of all of the cores on a CPU, the GPU speed-up was only ever a factor of two at most. In current systems, GPUs and CPUs are separate units with a relatively slow connection between them. The time spent transferring data over this connection can be considerable and must be minimised. The work required to do this resulted in complex code consisting of double the number of lines in the original - a far cry from minimising changes to the NEMO source. Finally, with the GPU-enabled routines merged back into NEMO, a speed-up of 25% was measured when a GPU was used to augment a single CPU core. We conclude that environmental codes such as NEMO that do not have a single bottleneck and require that data be frequently transferred between CPU and GPU are not well suited for making use of current GPU technology.
Organisation CSE , CSE-HEC , STFC
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Language English (EN)
Type Details URI(s) Local file(s) Year
Report DL Technical Reports DL-TR-2012-001. 2012. DLTR-20120-01.pdf 2012