Simon Willison’s Weblog

The One Billion Row Challenge in Go: from 1m45s to 4s in nine solutions (via) How fast can you read a billion semicolon delimited (name;float) lines and output a min/max/mean summary for each distinct name—13GB total?

Ben Hoyt describes his 9 incrementally improved versions written in Go in detail. The key optimizations involved custom hashmaps, optimized line parsing and splitting the work across multiple CPU cores.

# 7:08 am / go

Who Am I? Conditional Prompt Injection Attacks with Microsoft Copilot (via) New prompt injection variant from Johann Rehberger, demonstrated against Microsoft Copilot. If the LLM tool you are interacting with has awareness of the identity of the current user you can create targeted prompt injection attacks which only activate when an exploit makes it into the token context of a specific individual.

# 4:34 pm / ai, prompt-injection, security, llms, johann-rehberger