Equation 2 · The Hardest Unsolved Problems in Evaluating xAI's Claims
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giving 3.16 , = 10 , and 31.6 — which is a formal way of saying that even a well-resourced independent estimate of a frontier training run can be off by an order of magnitude or more, and everyone doing the estimating knows it going in. Epoch’s own account of its Grok 4 figures is direct about why: “the FLOP and GPU-hour estimates for Grok-4 are largely based on public statements from xAI, which are often vague,” producing significant uncertainty in the resulting compute total [ 4 ] . Their published point estimate — roughly 5.0×10²⁶ FLOP, built from about 246 million H100-hours — is a best reconstruction, not a confirmed figure, and Epoch says so on the page.
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