Tag: PhD

Jihye Kwon, a computer engineering PhD student, talks about her research projects and what it took to win a Best Paper award.

What drew you to computer engineering, specifically the application of machine learning to computer-aided design? What questions or issues do you hope to answer?

I was attracted to the concept of a computer: a machine that performs calculations. I found it very interesting how modern computers evolved from executing one instruction at a time to executing many instructions simultaneously by exploiting multiple levels of parallelism. Still, various challenges remained, or newly arose, so I dreamed about designing a brand-new computer system. That is what I had in mind when coming to Columbia.

At the beginning of my PhD, I experimented and learned how to design the core parts of special-purpose computers, using computer-aided design tools. I also explored machine learning from both theoretical and practical perspectives. These activities led me to work on my current research problems.

In advanced computer-aided design of computer systems, computers solve many complex optimization problems in steps to generate a final design. They do so as guided by the designers via means of the configurable ‘knobs’. My focus is on the designers’ work.

For a target system, designers run the computer-aided design tools repeatedly with the many different knob configurations until the tools output final designs with optimal or desired properties, e.g., in timing, area, and power. I wondered if machines can learn, from designers’ previous work, how to configure the knobs to optimize a new target system. Can designers virtually collaborate across time and tasks through the machine learning models? These are the main questions that I hope to answer.

Could you talk about your research and how you collaborated with other groups? Was this something you considered when applying to Columbia – that there are opportunities to do multi-disciplinary work?

When I was applying to Columbia, I wished I could have collaboration opportunities to study and work in the interdisciplinary research communities at the center of New York City. I wanted to explore applications of computer science in different areas to eventually gain insight and inspiration for my own research, which is centered at computer engineering.

Fortunately, these were realized as I worked with my advisor, Professor Luca Carloni. I was invited to join the project “Energy Efficient Computing with Chip-Based Photonics”, which is a part of a large initiative supported by the government and industry. In this project, I worked closely with Lightwave Research Laboratory in Electrical Engineering on a new optical computing system. We proposed the concept of a next-generation computing system that is co-designed with silicon photonics and electronic circuitry, in order to overcome the fundamental and physical limitations of today’s computers.

Another project on optical communication was initiated from a student project that I mentored in my advisor’s class, Embedded Scalable Platforms. This project investigated the use of photonic switches in optically-connected memory systems for deep learning applications.

Outside Columbia, I have also collaborated with researchers at IBM TJ Watson Research Center via my summer internships on the project of auto-tuning computer-aided design flows for commercial supercomputers. All these collaborations opened new horizons for me.

You won the MLCAD 2020 Best Paper award for your research, can you talk about your process – how did the research come about? How long did it take you to complete the work? What were the things you had to overcome?

In this work, I proposed a novel machine learning approach for computer-aided design optimization of hardware accelerators. I wanted to address this problem because it is computationally very expensive to explore the entire optimization space. It took me about one year to complete the work. One of the biggest difficulties I faced was the limited availability of the data for applying machine learning to the problem.

Then, I found out that transfer learning has been recently successfully applied in other areas with limited data. In transfer learning, a model trained for a related problem (e.g., natural image recognition) is transferred to aid the machine learning for the target problem (e.g., face recognition). Hence, I tried to apply transfer learning to my research problem. I trained a neural network model for a different accelerator design, and transferred the model to predict the design properties of a target accelerator.

However, the transferred model did not perform well in this case. I realized that due to the diverse characteristics of the accelerators, I needed to distinguish which piece of the source information should be transferred. Based on this intuition, I constructed a series of new models, and eventually, proposed one with promising performance. While it was a long process of building new models without knowing the answers, my advisor greatly encouraged me in our discussions to keep moving forward, and it was very rewarding in the end.

The Machine Learning for Systems session from the 2nd ACM/IEEE Workshop on Machine Learning for CAD (MLCAD) can be viewed here and the Best Paper announcement here. 

Looking back, how have you grown as a researcher and a person?

Besides expanding my problem-solving capabilities and technical skills, I have grown to be a better presenter and communicator. One of the tasks of a researcher is to explain one’s work to various groups and different types of audiences. I had a number of opportunities to present my work at academic conferences, seminars at companies, lightning talks, and annual project reviews. Initially, I struggled to meet the audience’s interests whose expertise spans a diverse range of areas and levels. Through those opportunities, I have received very helpful feedback, I have tried to ask myself questions from other people’s perspectives and progressively learned to keep a good balance between abstraction and elaboration.

Also, by interacting with a lot of students with heterogeneous backgrounds in the classes I TA’ed, I have learned to understand what their questions mean and where they come from. Based on that, I tried to adjust my answers to have more relatable conversations. From those conversations, sometimes the students found the topics very interesting, and sometimes I learned something new from them. It was such a great pleasure to inspire others and to be inspired. I think those experiences have made me a better researcher and person.

There are many organizations on campus, why did you choose to join Womxn in Computer Science (WiCS)?

In Fall 2017, I received an invitation from WiCS’ president, Julia Di, and was impressed by the passionate and caring board members working on the common goal of supporting the advancement of womxn in computer science. In my second year I launched the WiCS Lightning Talks for students with research experience to share their work and stories. The goal was for young students to get to know more about research and demystify the process.

I am one of the few women at Columbia in my research area of computer engineering and would like to contribute to inspiring the next generation to join us.

What was the highlight of your time at Columbia?

Every moment was special for me. Some of the highlights were during happy hour with members of the fishbowl. The fishbowl is a large office occupied by the majority of PhD students in computer engineering. We call it the fishbowl, because it is surrounded by large windows and students inside look like small fishes. Once, my colleagues talked about their memories of old computers that I had never seen. I enjoyed imagining the machines from their descriptions, and thinking about different types and generations of computers.

What is your advice to students on how to navigate their time at Columbia?

Explore, experience, and exploit. There are recommended lists of classes, activities, and companies, depending on your track and interests, but no one is exactly like you. There is such a great variety of opportunities and resources at Columbia and in New York City. I hope you can spend enough time exploring them and get involved in many ways before determining your academic and career goals.

Is there anything else that you think people should know?

Columbia is beautiful in the snow! It gets pretty windy in the winter, so please be aware if you are coming from warmer places. There are many places where you can study but Avery Library is my favorite library on campus. If you have any questions or opinions on this Q&A story, please feel free to drop me a line!