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Equation 4 · Part 2 · The Hardest Unsolved Problems in Evaluating xAI's Claims

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u3≈31.6u_3 \approx 31.6
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What this part means

Approximately equal to; the equality is not exact.

Its job in the formula

Approximately equal to; the equality is not exact.

The passage around this formula

giving u1u_1 ≈\approx 3.16 , u2u_2 = 10 , and u3u_3 ≈\approx 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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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.