The RETIS section¶

The RETIS section specifies settings for RE(PP)TIS simulations. Note that the section for TIS also needs to be defined for a RE(PP)TIS simulation.

Example RETIS section:

RETIS settings
--------------
swapfreq = 0.5
relative_shoots = None
nullmoves = True
swapsimul = True
rgen = None
seed = None

Keywords for the RETIS section¶

The following keywords can be set for the RETIS section:

Table 31 Keywords for the RETIS section.¶
Keyword	Description
nullmoves	Determines if we do null moves or not.
relative_shoots	Selects and defines relative shooting.
priority_shooting	Prioritize the ensembles with less cycles.
rgen	Determines the rgen to use in retis function.
seed	Determines the seed for rgen in the retis function.
swapfreq	Defines how often we perform swapping moves.
swapsimul	Determines if we swap multiple path ensebles at the same time or not.

Keyword nullmoves¶

nullmoves = boolean

If True we perform null moves in the ensembles not included in a swapping move. Otherwise, no move is done in these ensembles.

Default: No default, this setting must be specified.

Keyword relative_shoots¶

relative_shoots = None or list of floats

This keyword selects and defines relative shooting. Relative shooting means that the ensembles are shot in with unequal frequencies. This is selected by specifying the relative frequency for each ensemble in a list, e.g. relative_shoots = [0.1, 0.1, 0.2, 0.6] for four ensembles (one weight per ensemble, in interface order — the [0^-] minus ensemble first when it is present), where these numbers give the relative probability of the move being performed in that ensemble. The infinite-swapping scheduler that drives all path-sampling runs weights its per-ensemble move selection by these frequencies, so a heavier ensemble is worked on more often. The weights are state-independent, so every ensemble still samples its own path distribution and the computed rate is unchanged — only the allocation of sampling effort across the ensembles changes.

The weights need not sum to one (they are normalised internally); they must be non-negative with a positive sum. If relative_shoots = None (the default when the key is omitted) the ensembles are selected with the sampler’s own, roughly uniform, frequencies.

Default: relative_shoots = None (no relative shooting).

Keyword priority_shooting¶

Priority_shooting = boolean

This keyword automatically and dynamically internally select the relative shooting such that ensembles with a lower cycle number, will be prioritized until they reach a cyclen number equal to the others. This setting simplify the use of PyRETIS in cluster environments in which walltime is rather short. Each ensemble can be, therefore, investigated also if launching several runs.

Default: The default value is priority_shooting = False.

Keyword rgen¶

rgen = string

Select the function to use to generate the random number used in the retis function. That is, (1) the selection of the swap move vs shooting or time reversal, (2) detail balance for swap when Stone Skipping or Wire Fencing with high acceptance is used.

Default: The default value is rgen = None.

Keyword seed¶

seed = integer

Select the seed for the random number generator to be used in the retis function.

Default: The default value is seed = None.

Keyword swapfreq¶

swapfreq = float

This defines how often we perform swapping moves. This gives the percentage of swapping moves in the simulation, e.g.: swapfreq = 0.5 corresponds to 50% swapping moves, the 50% other moves will be TIS moves.

Default: No default, this setting must be specified.

Keyword swapsimul¶

swapsimul = boolean

If True several swaps are performed at the same time, that is we attempt to swap several pairs of path ensembles. If this is False, we will only attempt to swap one pair.

Default: No default, this setting must be specified.