A graphics-processor molecular-dynamics code stores a particle's velocity component…

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 graphics-processor molecular-dynamics code stores a particle's velocity component v=−850.0 m s−1v = -850.0\ \mathrm{m\,s^{-1}} in the half-precision format, whose significand (including the implicit leading bit) has t=11t = 11 bits. ((a)) State ϵM\epsilon_{\rm M} and uu for half precision. ((b)) Give the bound on the absolute error committed in storing vv that follows from the rounding model fl(v)=v(1+δ)\mathrm{fl}(v) = v(1+\delta), ∣δ∣≤u|\delta|\le u.

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