I build machine learning systems that waste less compute.

My research spans the inference and training stack: deciding when a small local model's answer is good enough before paying for a frontier one, packing training workloads onto partitioned GPUs, and simulating wafer-scale interconnects so runtime changes can be validated in minutes instead of days.

I studied Computer Engineering at Columbia University (B.S. 2026), where I published first-author work on GPU partitioning and fine-tuning efficiency with Prof. Martha Kim and IBM Research. At Cerebras Systems, I designed and built a simulator of the wafer-scale engine's interconnect from scratch — now part of how runtime engineers there diagnose throughput stalls on large models.

News

Publications

Escalator: Low-Cost Activation Probes for Local-to-Remote Model Routing

Connor Espenshade, Martha A. Kim

Preprint, 2026

Generate locally first, then decide. A lightweight probe over the local model's hidden activations scores each response (ROC-AUC 0.861 at detecting correctness) and escalates to a remote model only when the local answer looks insufficient, matching always-remote accuracy while escalating just 54% of queries.

prompt local model activation probe return · 46% answer escalate · 54% remote model answer
Fig. 1 — Every query is answered locally first; a lightweight probe over the local model's hidden activations decides whether that answer ships or the query pays for a frontier model.

Energy Efficient Scheduling of AI/ML Workloads on Multi-Instance GPUs with Dynamic Repartitioning

E. Lipe, N. Karia, C. Espenshade, C. Stein, A. Tantawi, O. Tardieu

IEEE International Symposium on Cluster, Cloud and Internet Computing (CCGrid), 2025

Treats a single MIG-partitioned GPU as a multi-objective scheduling problem under real diurnal datacenter load, with reinforcement-learning-driven repartitioning — 68% better on a joint energy–tardiness objective than an unpartitioned GPU.

Characterizing Training Performance and Energy for Foundation Models and Image Classifiers on Multi-Instance GPUs

C. Espenshade, R. Peng, E. Hong, M. Calman, Y. Zhu, P. Parida, E. K. Lee, M. A. Kim

Workshop on Machine Learning and Systems (EuroMLSys, at EuroSys), 2024

Measured six workloads, from 14M-parameter classifiers to 1.5B-parameter language models, across MIG partition mixes: heterogeneous partitions deliver up to 33% lower energy and 9% higher training throughput from a single GPU, and fine-tuning runs 55% faster at 42% less energy.

Earlier work, before ML systems: regenerative medicine at Penn's Singh Center for Nanotechnology (2021), and radio astronomy — modeling Jupiter's synchrotron radiation with NASA JPL collaborators (ATOM, 2020) plus two star-cluster studies (SAS, 2020).

Systems

Selected engineering work, from silicon to kernel to runtime.

Wafer-scale interconnect simulator Cerebras Systems, 2025

Before this existed, validating a runtime change meant a 24-hour run on wafer hardware. I designed and built a C++ simulator of the wafer's inter-die fabric from a blank file: every region, core, and wire, with backpressure from link capacities and delays, so simulated throughput and stalls track the real machine. Iteration dropped to 5 minutes (288x), and the simulator surfaced KV-cache token drops, batching inefficiencies, and race conditions on production-scale models. Hardware, systems, and ML teams adopted it, and engineers I onboarded kept extending it after my internship ended.

Transformer accelerator on ESP Columbia, 2025

Extended the HLS4ML compiler with custom C++ translators for matmul and transpose, implementing the hardware primitives transformer attention needs on FPGAs within the open-source ESP SoC platform. Report

FPGA CNN accelerator Columbia, 2025

Hardware/software co-design in SystemVerilog and C running an int8-quantized TensorFlow CNN (scales and zero-points handled in hardware), reaching a 3.4x convolution speedup at 30% device utilization. Presentation

Linux kernel scheduler & filesystem Columbia, 2024

A custom priority scheduler (+75% throughput on mixed workloads) and a complete read/write filesystem, both implemented in-kernel in C. Notes

Robotic patch-clamp orchestration Columbia Bioelectronic Systems Lab, 2024

Real-time control software coordinating ten lab devices, including manipulators, pumps, and cameras, to 1.0 µm precision for automated patch-clamp electrophysiology. GitHub

Archive

Where this started.

Apple WWDC scholarship 2018

One of 350 students worldwide selected for a physics-based game simulating collisions and gravity, written in Swift. Apple flew me to San José as a high-school freshman. Code

Connor outside the San Jose McEnery Convention Center at WWDC 2018

Leaning Eagle 2017–2019

An iOS ordering app for my high school's coffee bar — Stripe, Apple Pay, CloudKit, and AWS Lambda — that ran in production on the App Store through two years of daily lunch rushes.

Leaning Eagle iOS app screens: menu, espresso order with Apple Pay, and smoothie customization

FIRST Robotics vision 2019

Real-time object tracking running on an iPhone mounted to a competition robot, streaming target poses over TCP to the drive controller. GitHub

iPhone app tracking a vision target with confidence and angle readouts

Also from those years: augmented-reality turn-by-turn navigation prototypes, and websites built and delivered for local clients.

Contact