When Serving Costs More Than Training

Kaplan et al. estimate a transformer's non-embedding compute at about 2N2N FLOPs per token for a forward pass, with the backward pass costing roughly twice the forward pass, giving C≈6NDC \approx 6ND FLOPs to train NN parameters on DD tokens.

A 7B model is trained on 2T tokens and then deployed. How many tokens must it process at inference before serving compute equals training compute?

A

The break-even is never reached: training compute exceeds lifetime serving compute for any model.

B

About 6 trillion tokens: training costs 6×7e9×2e12=8.4e226 \times 7\text{e}9 \times 2\text{e}12 = 8.4\text{e}22 FLOPs and each served token costs about 2N=1.4e102N = 1.4\text{e}10, so three served tokens per training token.

C

About 2 trillion tokens, one served token per training token, since a served token costs the same 6N as a training token.

D

About 6 trillion prompt tokens, but generated tokens are free, because the KV cache removes their matmuls.