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Equation 14 · Part 2 · The Real Economics of Shipping a Model to a Device

Symbol C_device

TCdevice=Cdev+U+Q⋅cd,TCcloud=Q⋅ccloud,TC_{\mathrm{device}} = C_{\mathrm{dev}} + U + Q \cdot c_{d}, \qquad TC_{\mathrm{cloud}} = Q \cdot c_{\mathrm{cloud}},
CdeviceC_{\mathrm{device}}

What this part means

CdC_device is part of the quantity the equation computes from the expression on the right.

Its job in the formula

CdC_device is part of the quantity the equation computes from the expression on the right.

The passage around this formula

Define CdevC_{\mathrm{dev}} as the fixed, per-release engineering and QA cost of producing and validating the device-tier variant matrix described above — the harness time, the pass/fail sign-off per tier, per quantization scheme, per chip target. Define U as the cost of distributing model updates to the installed fleet, expanded in the next section. Define cdc_{d} as the marginal cost of one additional on-device inference and ccloudc_{\mathrm{cloud}} as the marginal cost of one additional cloud-served inference of the same model. Total cost over Q queries under each placement is TCdevice=Cdev+U+Q⋅cd,TCcloud=Q⋅ccloudTC_{\mathrm{device}} = C_{\mathrm{dev}} + U + Q \cdot c_{d}, \qquad TC_{\mathrm{cloud}} = Q \cdot c_{\mathrm{cloud}}. and the break-even query volume — the point at which on-device placement stops costing more than cloud…

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