pyhande.weight¶
Attempt to remove the population control bias by reweighting estimates.

pyhande.weight.
reweight
(data, mc_cycles, tstep, weight_history, mean_shift, weight_key='Shift')¶ Reweight using population control to reduce population control bias.
Reweight estimators linear in the number of psips by the factor:
\[W(\tau, N) = \Pi^{N1}_{m=0} e^{A \delta \tau S(\tau  m\delta\tau)}\]where \(A\) is the number of steps per shift update cycle, \(\delta\tau\) is the time step and \(S(\tau  m\delta\tau)\) is the shift at time \(\tau  m\delta\tau\), and \(m\) is the number of iterations to reweight over.
See [Umrigar93] Eqs. 1420 for details and [Vigor15] for use in FCIQMC.
Parameters:  data (
pandas.DataFrame
) – HANDE QMC data.  tstep (float) – The time step used in the weight factor.
 mc_cycles (int) – The number of monte carlo cycles per update step.
 weight_history (integer) – The number of iterations to reweight over.
 mean_shift (float) – The mean shift. Used to prevent weights becoming too big.
 weight_key (string) – Column to generate the reweighting data.
Returns: weight – List of weights.
Return type: List[float]
References
 Umrigar93
 C.J. Umirigar et al., J. Chem. Phys. 99, 2865 (1993)
 Vigor15
 W.A. Vigor, et al., J. Chem. Phys. 142, 104101 (2015).
 data (