CU Index Explainer

A toy compute market: three providers, two GPUs each, twelve days. Every number on this page is computed live with the same rules as cu-index, so you can watch a day get built and then break it on purpose.

Level, in $/CU·hr

Answers: what does a CU-hour cost today?

  • Mean of the listings present today, each as price ÷ CU score
  • Moves when the roster changes, on purpose
  • Not published on a thin day

Index, chained from 100

Answers: how much has the price changed?

  • Geometric mean of matched listing relatives, chained
  • Blind to the roster: a listing counts only against itself
  • Carries flat on a thin day

1. Raw listings and matching

A listing is one key: provider, GPU, instance, region, price type. Today's price is compared to that same listing's price on its last ok day. If the listing has no earlier ok price, it isn't matched and contributes nothing today.

2. Relatives, geometric mean, chain

Relative r = today ÷ reference. The CU score is in both, so it cancels: r is the same in $/hr or $/CU·hr. Provider relative = geometric mean of its listings' r. Market relative = geometric mean of the provider relatives. Then multiply yesterday's index by it.

3. Quality grade

Before the day is allowed to chain, its basket is compared to a baseline: the median basket over the last seven ok days. Three floors, each gated separately. Below any floor the day is thin: the index carries flat and no level is published. Nothing matched at all is a gap.

Glossary

listing
One product key: provider, GPU, instance, region, price type. Identity is canonical across collectors.
reference price
The listing's own price on its most recent ok day, up to 45 days back. Not simply yesterday.
matched
Present today and has a reference price. Only matched listings make relatives.
relative
today ÷ reference. 1.0 means unchanged. Multiplicative, so averaged geometrically.
chain
index[t] = index[t−1] × market relative[t]. Each day is measured against the basket that existed both days.
level
Mean $/CU·hr across cells present today. Honest about today, not about change.
thin
Basket below a floor versus baseline. Index carries flat, level withheld. The move that happened inside the hole is measured on the recovery day via the lookback.
gap
Nothing matched. Index null, line breaks.
chain drift
What you lose if a move is never measured: a chained index can end somewhere a fixed-base index wouldn't. The lookback is the defence.