You're given a compute kernel and a cycle-accurate simulator that verifies functional correctness and reports runtime. Within two weeks, achieve the largest speedup without changing outputs. Describe your end-to-end plan: establish a baseline, profile to find bottlenecks, form hypotheses, choose data-layout transformations, use bitwise operations and hashing where helpful, and apply VLIW-style instruction scheduling to exploit instruction-level parallelism. Explain how you validate correctness after each change, avoid overfitting to the simulator, and quantify speedup improvements. Prioritize the first three optimizations you would try and justify them.

This question evaluates performance engineering and low-level kernel optimization competencies, including profiling, data-layout and instruction-level techniques, correctness verification, and benchmark-driven measurement within the System Design domain.

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This is a hard difficulty System Design question, commonly asked during Onsite rounds at Anthropic.

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This question is commonly asked for Software Engineer candidates at Anthropic during technical interviews.

Optimize a compute kernel with a simulator | Anthropic Interview Question

Performance Optimization Plan for a Compute Kernel

Context

You are given:

A compute kernel (single critical function or set of loops) to optimize.
A cycle-accurate simulator that both verifies functional correctness and reports runtime/cycle counts.

Goal: Within two weeks, achieve the largest possible speedup without changing the kernel's outputs.

Task

Describe your end-to-end plan to:

Establish a reproducible baseline.
Profile to find bottlenecks and form hypotheses.
Select and apply optimizations, including:
- Data-layout transformations.
- Strength reductions via bitwise operations.
- Hashing where helpful.
- VLIW-style instruction scheduling (manual ILP and software pipelining).
Validate correctness after each change.
Avoid overfitting to the simulator.
Quantify speedup improvements.

Requirements

Outputs must be identical to baseline.
Prioritize the first three optimizations you would try and justify them.
Explain how you will measure and report gains after each change.

Task

Describe your end-to-end plan to:

Establish a reproducible baseline.

Profile to find bottlenecks and form hypotheses.

Select and apply optimizations, including:

Data-layout transformations.
Strength reductions via bitwise operations.
Hashing where helpful.
VLIW-style instruction scheduling (manual ILP and software pipelining).

Validate correctness after each change.

Avoid overfitting to the simulator.

Quantify speedup improvements.

Optimize a compute kernel with a simulator

Quick Overview

Performance Optimization Plan for a Compute Kernel

Context

Task

Requirements

Solution

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Optimize a compute kernel with a simulator

Quick Overview

Performance Optimization Plan for a Compute Kernel

Context

Task

Requirements

Solution

Comments (0)