A laser rangefinder measures a distance and the reading is stored in the binary32…

PHYSICS · Multi-part · Fermi University Physics · Mathematical Methods for Physics · Numerical and computational mathematics · Numerical and computational mathematics

Error, Chance and the Machine, Ch Rounding, backward error and the sensitivity of a computation

Problem

A laser rangefinder measures a distance L=12345.6 mL = 12345.6\ \mathrm{m} and the reading is stored in the binary32 (single-precision) floating-point format, for which the significand (including the implicit leading bit) has t=24t = 24 bits. ((a)) State ϵM\epsilon_{\rm M} and uu for binary32. ((b)) Using the rounding model fl(L)=L(1+δ)\mathrm{fl}(L) = L(1+\delta) with ∣δ∣≤u|\delta|\le u, give the bound on the absolute error committed in storing LL.

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