Roofline model: definition · Chip Field Guide

Beginner

A simple chart that shows whether a job is limited by how fast the chip can calculate or by how fast it can fetch data.

Novice

A chart of the best speed a chip can reach on a task: attainable performance is the smaller of peak compute and $\text{memory bandwidth} \times \text{arithmetic intensity}$ . On log-log axes the limit looks like a roof: a sloped line (limited by memory) meeting a flat one (limited by compute).

Expert

The ridge point, $\text{peak compute} \div \text{bandwidth}$ , is the lowest arithmetic intensity at which a task can reach peak. Lower “ceilings” show the limit when an optimization is missing. For chips with several memory levels, draw one roofline per level (DRAM, on-chip SRAM).