How biased is a short digital-twin run that starts from a default state?

research/warmstart-twin

Cold-start bias of short twin runs: exact AR(1) bias/variance/warm-up deletion, M/M/1 empty-start bias constant ρ/(1−ρ)³, negligible at valid-interval lengths but −5.6 of 9 at 50 jobs; MSER-5 did not help.

10 tests

What it found

A twin reset to an empty queue and averaged over n steps is biased toward that start. For AR(1) output the bias, variance and best warm-up deletion are exact (bias/sd 1.88 to 0.12 for n=20 to 2500 at φ=0.9). For the M/M/1 wait the summed empty-start bias is ρ/(1−ρ)³ (verified numerically against an exact series and coupled simulation), so it equals one standard deviation only at 23 jobs at ρ=0.9: at run lengths that give a valid interval it costs 1–3 coverage points. Short runs are different: 50 jobs from an empty start read 5.6 below the true mean wait of 9; starting at the mean reduces bias but not reliably RMSE; a noisy real-state start is unbiased with 3.6× the sd; MSER-5 truncation made bias and coverage worse here. Stylised (AR(1) and M/M/1, simulated “real” system).

A figure from its own output

Figure produced by research/warmstart-twin: bias_vs_n — warmstart-twin/experiments/bias_vs_n.svg, written by the project's own experiment code.

Paper, code and results

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.