Ten minutes with...Santhosh Rethinagiri, Barcelona Supercomputing Center
Santhosh Rethinagiri is a senior researcher with the Microsoft research group in Barcelona Supercomputing Center (BSC). His research interests involve minimisation of energy for data centers, power reduction for supercomputers with mobile computing chips and a FPGA-based acceleration for databases. Fellow BSC researcher Oscar Palomar also participates in the ParaDIME project, while the principal investigators are BSC’s Adrián Cristal and Osman Ünsal.
What’s your research background? How did you come to be working in this field?
I did my B.Eng in electronics and instrumentation before specialising in embedded systems for my MS in electrical engineering. After that, I spent time working for the electronic system-level (ESL) company Synopsys, where I got to know about system research, platform architecture in general and the products which they offer in particular. My PhD, which I studied at Inria, in France, focused on developing tools to estimate power for applications and systems used by various companies, including Thales, Inpixel, Inria and STMicroelectronics.
What are your current research interests?
My work is mostly in power estimation and optimisation across every step of the computing system, from hardware to applications. I undertake heterogeneous prototyping with field-programmable gate arrays (FPGAs), central processing units (CPUs) and graphic processing units (GPUs). This involves running real applications and trying to optimise them for different devices, aiming to use the advantages of the three different devices to improve energy efficiency and accelerate applications. I am also working at the device level for hybrid architectures, using complementary metal-oxide-semiconductors (CMOS).
In terms of software, I am working on annotated power saving. A piece of software will specify that an application should be executed on a specific frequency, but some applications don’t require that much power so you can use automatic workload specification to intelligently distribute power.
Why should we be working towards more energy-efficient computing systems? What can we do to make them more efficient?
Currently, data centres are not operating fully: up to 90% of their processors may be idle at any one time. This leads to enormous energy costs.
One way to reduce the power consumption is to replace powerful processors with embedded ones, gaining a productive trade-off of energy versus performance. The Mont-Blanc project at BSC, for example, is creating supercomputer prototypes where high-performance processors are replaced with ARM-based chips. Where software is concerned, annotating the sections which are critical and therefore need high performance and those which need less power can help reduce the power consumption, as mentioned above.
What, for you, are the main technical challenges which should be tackled in order to achieve these?
For me the key thing is that every part of the design of computing systems needs to be addressed: improved architecture should be complemented by software and device design. As no one person can master every element, this means that engineers from different areas need to work together, and this is what the ParaDIME project is all about.
On what areas are you concentrating in the ParaDIME project?
Within the project I concentrate on architecture. My first task was to develop power models for different kinds of processor and automatically evaluating these models. Next, I’ve been building heterogeneous platforms consisting of the three different processor types listed above, both high-performance and embedded systems. These will define how future architectures are designed.
We are also working on a proposal for a hybrid device combining two different types of processor, such as CMOS and tunnel field-effect transistors. We’ve been modelling designs with the help of a Belgian research institute, the Interuniversitair Micro-Electronica Centrum (IMEC).
We’re lucky to have a cooperative working environment in the ParaDIME project, as well as strong project management, which means that everything is well coordinated.
What do you think BSC’s unique contribution to the ParaDIME project is?
As the coordinator, BSC is the heart of the project, both in terms of project coordination and the new research it is producing on different topics. The fact that there is a supercomputer on site at BSC means that researchers can experiment with their own prototypes. There is also expertise in every field at the centre and researchers are very approachable. We swap advice and share code with researchers from the Mont-Blanc project –we’ve asked for their input about their prototypes, for example, which has influenced our development of a data centre prototype. We also work with the programming models group: their programming models can be accessed for FPGA and GPU communication.
Why is the ParaDIME project important? What do you think the most important results will be for society in general?
ParaDIME will provide new roadmaps for data-centre systems, covering programming models, runtime models, new devices (both in the near and distant future). Testing with prototypes gives us the assurance that these will work. The project won’t change the face of data centres, but at least it will provide one of the solutions contributing to energy-aware computing.
Why is it important for ParaDIME to participate in the ICT-Energy project?
In ICT-Energy, a consortium of projects related to energy, the projects start from basic physics and go all the way up to data centres and modern supercomputers. ParaDIME is the only one working on all aspects from the device to data-centre level, so acts as a kind of middleman for the other projects, and the other projects give their inputs on how to utilise small architectures.